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All Springer/NP/PCP Air Gun Discussion General => European/Asian Air Gun Gates => China/Asian AirGun Gate => Topic started by: Scotchmo on October 27, 2011, 02:15:16 PM

Title: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on October 27, 2011, 02:15:16 PM
I am going to contribute my findings. Anyone else is welcome to do the same. Hopefully, no drama, just facts.

Can any spring airgun be easily converted to a gas spring?

Some airguns lend themselves to easy conversion. Some do not. If the airgun uses a latching rod down the center of the piston, then it is NOT a good candidate. If the piston has a perimeter latching sear, than it can be a simple conversion. So, good news for all the rifles that can use a GRT trigger. They should be fairly easy to convert. Some of the Chinese copies of high end European rifles use a latching rod so they are not good candidates. Sorry B21, B30, B40 owners.

What kind of special tools are needed?

A spring compressor is a good idea, but once you remove the wire spring, you really only need a simple bar clamp. The amount of preload on a gas spring is small so you do not need a long throw spring compressor to reassemble the rifle. A metal lathe is helpful for making the necessary spacers, top hats and bushings. But some clever use of flat washers, spacers, drill, and a hacksaw can also work. There have been a couple of instances where I was lucky and the gas spring fit with no spacers or bushings.

The gas spring can be installed in either direction. The combined weight of the piston and tophat can affect performance. When you install the spring "backwards" (spring body inside piston), you may be increasing the weight of the piston more so than if you install it "front facing" (spring shaft projecting into piston). I prefer to install the spring "front facing" but a "backwards" installation is often simpler and the spring body will not scrape the piston wall when you cock or fire. If you install it "front facing" you need to use bushings/washers to keep the spring centered. A "front facing" gas spring gives you more control over the combined piston weight.

What kind of gas spring should I use?

The gas springs that will work best are NOT automotive gas springs. Lift struts probably will NOT do the job. Some people have adapted Crosman gas springs. I am not familiar with the specifications of the Crosman gas springs and I have not been able to find any published information on them. But obviously they work. Industrial gas die springs will work. They are high quality so they should last. Detailed specifications are available which makes selection of the appropriate spring easier.

There are a number of manufacturers of gas die springs:

N-Forcer (USA)
Dadco (USA)
Kaller (Sweden)
ASRaymond (Kaller rebadge?)
etc.

http://www.n-forcer.com/content/pdf/Mini.pdf (http://www.n-forcer.com/content/pdf/Mini.pdf)
http://www.dadco.net/Catalog%20PDF/micro_catalog_revC.pdf (http://www.dadco.net/Catalog%20PDF/micro_catalog_revC.pdf)
http://www.asraymond.com/documents/Counterbalance%20Solutions%202012%20Web.pdf (http://www.asraymond.com/documents/Counterbalance%20Solutions%202012%20Web.pdf)

Some of the manufacturers may not deal directly with end users so you might have to find a distributor. McMaster has a few, though limited to shorter stroke spring guns.

http://www.mcmaster.com/#6643k561/=eo9zhf (http://www.mcmaster.com/#6643k561/=eo9zhf)

Which model springs should I use?

That will depend on the rifle. Most of the rifles that we are considering here use a 1inch (25mm-26mm) piston. The 19mm diameter gas springs fit nicely in these pistons. There are probably three different strokes of the 19mm diameter springs to consider. Low power, short stroke rifles will use the 80mm stroke gas springs. Medium power rifles will use the 100mm stroke gas springs. High power rifles will use the 125mm stroke gas springs.

19mm-080mm = QB36-1, QB57, QB58, TF58, TF67, TF97, etc.
19mm-100mm = QB36-2, TF99, medium power Gamos, etc.
19mm-125mm = AR3000, TF87, etc.

Besides the size of the gas spring, you have to specify a force. They are rated by PSI, BAR, Lbf., Newtons, etc. The lbf. is what I use to calculate which spring might work best in a given instance. So you can do the math and choose it that way. Or - they also include a simple color coding system. Springs can come from different manufacturers, but if they have the same color code, they are generally interchangeable as far as approximate force. Color is usually indicated by a colored shaft seal or a colored label.

Green label - very low force, too low for most airguns, but still usable. - not recommended
Blue label  - good for airguns that need to be smooth.
Red label -  good for airguns that need to be powerful
Yellow label - very high force, too high for most airguns, but still usable. - not recommended

I have found the Blue and Red label gas springs to be good choices for airguns. You can get the most power from the Yellow label spring but there will be consequences from the excess force. Most manufacturers also have a Black label spring. That merely indicates a custom force that can be anywhere between the Green and Yellow ratings. Some gas springs are even adjustable but you will need to buy the charging equipment.

What does a gas spring cost?

Probably $40-$100 depending on the source.

There are some companies that will install gas springs in your airgun for you. Pyramyd air does a few models but they give no details on the type of gas spring that they use. It looks like Mike Melick is now converting some of the Chinese airguns. The dealer/tuner installed springs seem to run $100+.

Gas springs have some advantages over wire springs. I like them a lot so far. But they are not a cure all. Sometimes wire springs are more appropriate.

-Scott Hull
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Addictedtoair on October 27, 2011, 02:30:18 PM
Thank you for sharing your information in a well written and understandable manner.

Brett
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Onebaddj on October 27, 2011, 04:18:31 PM
Awesome info. Thanks for sharing it.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: gene_sc on October 27, 2011, 05:11:14 PM
Fantastic compilation of information Scott. May I place this information in the GTA Library?

Thanks so much for a valuable contribution.

Gene
Title: Re: Chinese air rifles and Gas spring conversions
Post by: amb5500c on October 27, 2011, 05:48:00 PM
Very well done sir. Easy to understand and well written.
Richard
Title: Re: Chinese air rifles and Gas spring conversions
Post by: z28rod on October 27, 2011, 06:00:38 PM
Man I really learned alot from that post, excellent.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: stilkikin on October 27, 2011, 09:08:10 PM
Great post. You make things easy for people like me!
Title: Re: Chinese air rifles and Gas spring conversions
Post by: bradyman1 on October 27, 2011, 09:09:50 PM
Thanks for the info. Very well written and VERY informative.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Smackey54 on October 27, 2011, 09:20:06 PM
Thank you Scott! Nice job! Do you write for a living? Technical writing for dummies like me? If not, you should!
Thanks again!
Title: Re: Chinese air rifles and Gas spring conversions
Post by: supertech77 on October 27, 2011, 11:40:31 PM
great post ,very informative,very organized and factual 'thank you. 8)
Title: Re: Chinese air rifles and Gas spring conversions
Post by: gamo2hammerli on October 27, 2011, 11:42:50 PM
That's an excellent and informative post...great for do-it-yourselfers who want to convert to nitro piston power.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on October 27, 2011, 11:43:38 PM
GREAT POST !!!

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on October 28, 2011, 12:51:47 AM
Fantastic copulation of information Scott. May I place this information in the GTA Library?

Thanks so much for a valuable contribution.

Gene
Please do so. It is my pleasure to be able to contribute to the GTA library.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: redone1992 on October 28, 2011, 09:13:24 AM
excellent and informative post
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Kailua on October 29, 2011, 04:11:18 AM
Always wondered where to get gas pistons.  Thanks for taking the time and effort to bring this to our attention.  Have this bookmarked.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: z28rod on October 29, 2011, 05:57:12 AM
Scotchmo , do you think you could post some of your info. on what manuf. springs fit what rifles that worked safely ?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on October 29, 2011, 04:52:35 PM
Scotchmo , do you think you could post some of your info. on what manuf. springs fit what rifles that worked safely ?
Die springs are standardized parts in the tooling industry. A 19x080 spring from one manufacturer is interchangeable with a 19x080 spring from another manufacturer. Kind of like ball bearings or nuts and bolts. Any spacers or adapters that you make for one spring should fit the other regardless of the source. There can be very small differences in external dimensions but usually inconsequential. I have tried N-Forcer, Dadco, and Kaller/ASRaymond/McMaster. All interchangeable.

So far I'm preferring to use the N-Forcer products. It seems to be a smaller company that is willing to deal directly with end users. Just deal with them in a professional manner and it should go fine. They cost about $45+/- for the airgun sizes and they give a small discount for ordering 10+ of any one item.

I have not been doing this long enough to have any kind of definitive list of airguns that can be converted. Just that 19mm OD springs seem to work in most of the Shanghai rifles.

I have worked a lot with the QB57 and TF58. The 19x080 size spring works well in these particular short stroke rifles. They use separate spring guides so no cutting is involved. I am going to use a 19x100 spring to convert my TF99 next but I think it has an integral plastic spring guide that will have to be cut off. You mentioned "safely". The only safety consideration I had was when trying to cock a rifle with the yellow label spring installed. The QB57 with the yellow spring actually performed well. Fairly smooth shot cycle and gave 780fps with medium weight .177 pellets. That was a 130fps increase. Still, it was a bear to cock. Too high to be acceptable. Maybe a long stroke underlever would be easier to cock. But you would still be stressing the other components way beyond what the original designers intended. I think if you stick with the red or blue label springs, you should be "safe".
Title: Re: Chinese air rifles and Gas spring conversions
Post by: z28rod on October 29, 2011, 07:14:07 PM
"I am going to use a 19x100 spring to convert my TF99 next"
Can you post how it works out with that tf99, i have a tf99 also, would be nice to see how it works.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: lurch420gam on October 31, 2011, 03:15:13 PM
Thanks for the excellent information. Great post! Joel
Title: Re: Chinese air rifles and Gas spring conversions
Post by: gene_sc on October 31, 2011, 10:27:44 PM
All this is great informtion and I do respect your research but, I would have to say that messing with using these rams or springs you mention in a QB-57 -58 is treading dangerous ground. As it is now, the trigger system is almost to weak for the stock spring they use now. I would recommend staying away from any power mods on the QB's. One could lose a finger very easily on these models.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 01, 2011, 12:27:43 AM
All this is great informtion and I do respect your research but, I would have to say that messing with using these rams or springs you mention in a QB-57 -58 is treading dangerous ground. As it is now, the trigger system is almost to weak for the stock spring they use now. I would recommend staying away from any power mods on the QB's. One could lose a finger very easily on these models.
True. Be careful. Messing with any stored energy device of this level can be dangerous. Gas spring or wire spring. That is why I suggested the Blue and Red label gas springs. They are the closest to the stock spring as far as stored energy. A small increase (10-20%) beyond stock is about as much as I would feel comfortable attempting. I felt a little uneasy testing the Yellow spring. And I never let go of the cocking lever when it is retracted. The Yellow spring was removed right after an hour of testing as I did not want it used anymore.

Total spring energy when cocked:
N-Forcer 19x080 BL - 27 ft-lb
Stock TF58 spring - 36 ft-lb
N-Forcer 19x080 RD - 40 ft-lb
N-Forcer 19x080 YW - 54 ft-lb - not recommended

Maximum return force:
N-Forcer 19x080 BL - 130 lbf.
N-Forcer 19x080 RD - 195 lbf.
Stock TF58 spring - 212 lbf.
N-Forcer 19x080 YW - 260 lbf. - not recommended

The gas spring produces a more constant force throughout its stroke. That is why it can deliver more total ft-lbs of energy with a lower peak spring force. The TF58 trigger system is a copy of the Gamo trigger system. I have a GRT trigger installed. The trigger system is adequate for springs that are close to stock as far as force. The Blue and even the Red label gas springs have less trigger load than the stock spring. I am not doing, and I don't advocate doing this as a way to increase the power a large amount. A small increase would be nice but my main goal is to have an improved shot cycle. The gas spring produces no torque when extending. That increases accuracy and can decrease hold sensitivity. I know that careful lubing and tuning using a wire spring can minimize the torque, but the gas spring eliminates it.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: gene_sc on November 01, 2011, 01:07:51 AM
You data and what you have posted is very intriguing to say the least. With my R&D using the Crosman NPSS, NP and XL gas rams has been quite an exciting exercises in performance. Although I do not know what these gas rams are rated at I have found they work consistently well with the conversions I have done. Especially on the Stoeger, and older Daisy's. One issue is room for the rams in certain instances. I have had to re design a couple springers in the trigger and spring block section on a couple when using the XL rams due to length.

I would love to be able to converse with these people and find out if the pressures can vary with the different length strokes of the piston. For example can these rams be ordered with different pressures of nitrogen in different overall lengths. There is a world of things a tuner can do with many of the non piston seer style springers.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 01, 2011, 01:52:21 AM
I don't know about custom lengths, but you can order custom pressure within the allowable range. The 19mm diameter springs go up to about 260lbs. Does the NPSS and XL use a larger diameter piston? The next size up in gas springs is 25mm and they are available in longer strokes. Maybe these larger gas springs would work in the rifles with larger pistons.

There is a limited selection of standard strokes so I pick the one with a stroke that is just a little longer than the stroke in the particular rifle. I'm lucky in that the rifles that I have been working on match up fairly closely with the standard gas piston stroke lengths. I leave a little room for preload so that the spring does not experience damaging "top out" during firing or "bottom out" during cocking. The spring usually has to be spaced up to fit. If a particular spring does not quite have enough travel, and the next size up won't fit, I think I could add a spacer under the piston seal in order to shorten the stroke of the rifle slightly. Like you said, the spring block might need to be drilled or cut back to add a little space if the gas spring is a little too long. I have not had to do this yet, though I will have to cut down the spring guide in my TF99.

I suspect that the Crosman springs may be based on dies springs. Maybe they use custom lengths. I'm curios if they are the same dimensions as stock die springs. Compare them to those in the die spring catalogs that I linked to. You can check the force with a bathroom scale and a press. Dies springs are high friction devices. The compression force is significantly higher than the extending force. So you have to release the press slightly to get an accurate measurement of extension force.

What do you mean by "non piston seer style springers"?

I too have been learning a lot and having fun experimenting with these combinations of low priced rifles and high quality gas springs.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 08, 2011, 03:49:26 PM
Here is some interesting test data:

Rifle: TF58

Pellet: AA 7.33g

Blue label 19x080 ASRaymond gas spring, strut forward, heavy tophat - 670fps average
Red label 19x080 N-Forcer gas spring, strut forward, heavy tophat - 730fps average
Red label 19x080 N-Forcer gas spring, strut forward, light tophat - 710fps average
Red label 19x080 N-Forcer gas spring, strut backward, maximum spacer weight - 770fps average

Putting the strut in backwards is actually easier and in this case, the added piston weight improves performance. Adding weight to the piston assembly does not always increase performance and sometimes makes the shot cycle harsher. I still need to do a good accuracy comparison, but the shot cycle still seems OK. So for now my preferred way to mount the gas springs is with the spring body inside the piston.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: z28rod on November 10, 2011, 10:32:16 AM
Scotchmo can you post some pics of the process it would help to see what your doing alot thanks.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 0351_Vet on November 10, 2011, 11:03:09 AM
Great Post.....Lots of info.

Question: What is the advantage of a Gas Spring over a Conventional Spring?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on November 10, 2011, 01:58:15 PM
The two obvious advantages to a gas spring:

It can be left cocked indefinitely without harm....
It has no "torque" (twisting) reaction when firing....

One disadvantage:

It will change in power in relationship to the absolute temperature because the internal pressure changes....

I'm sure there are other effects that can be argued, but those are the obvious ones from a quick look....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 0351_Vet on November 10, 2011, 02:08:22 PM
So....Do you like Gas Springs over Springers Bob?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on November 10, 2011, 02:25:35 PM
Never had one....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 10, 2011, 07:47:56 PM
Scotchmo can you post some pics of the process it would help to see what your doing alot thanks.
The pictures are of a QB57. I picked it to show since it is easier to disassemble than the TF58 (no scope to deal with). The two actions are almost the same. The only difference in the parts is that the spacer for the end of the gas spring needs to be a little longer than the one for the QB57. The action of the QB57 is about 3/8" shorter than the QB58. The stroke is about the same. The spacer for the QB57 is .28" long. It is 3/4" diameter with a .81 diameter lip at the start that keeps it centered in the piston. The spacer has a countersunk recess for the screw that holds the spacer onto the gas spring. That is how I did it. I have a lathe to make the parts but if you don't, there are many other ways to center the gas spring and space it to the correct length.

The first picture shows the ASRaymond/McMaster blue label 19x080 gas spring, the top hat/spacer and the spacer screw. These are the only parts that were added. You can discard the original wire spring, top hat and spring guide.

The second picture shows the gas spring assembly.

The third picture shows how the gas spring rod nests into the spring cap. The QB/TF/5758/67 need no other modifications. On other models, you may have to cut off the plastic spring guide and make a metal spacer to center the rod.

The forth picture shows the gas spring being inserted into the action.

The last picture shows the cap in place before compressing. There should be at least a small amount (maybe 1/8") of preload in the gas spring to prevent it from topping out when the rifle is fired.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: z28rod on November 10, 2011, 09:05:47 PM
Thank you Scotchmo , this is very cool. So what kind of fps does that give you on the qb57 ? is it 177 or 22 cal. That would be a cool rifle at 700 + fps in .22 cal.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 10, 2011, 09:21:25 PM
Thank you Scotchmo , this is very cool. So what kind of fps does that give you on the qb57 ? is it 177 or 22 cal. That would be a cool rifle at 700 + fps in .22 cal.

The .177 QB57 that currently has the "Blue" ASRaymond spring is shooting 7.33 grain AA Falcons at 720fps average. It is lighter than the stock spring so very easy to cock.

The .177 TF58 that currently has the "red" N-forcer spring is shooting the same pellet at 776fps average.

These rifles have fairly small chamber volumes. So they are well suited to .177 caliber. A .22 QB57 would probably max out around 600fps with 14-15g pellets.

Title: Re: Chinese air rifles and Gas spring conversions
Post by: bang45 on November 15, 2011, 09:32:10 AM
The best info for airgun enthusiast!
Title: Re: Chinese air rifles and Gas spring conversions
Post by: z28rod on November 15, 2011, 05:01:10 PM
That is still a decent velocity 600 fps .22 cal. qb-57.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: pappa on November 16, 2011, 01:43:30 PM
Does anyone know if it is possible to convert a B25 or B28 to gas piston?
Thanks for any helpful contribution.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 16, 2011, 02:04:47 PM
Does anyone know if it is possible to convert a B25 or B28 to gas piston?
Thanks for any helpful contribution.
Short answer - No

Although anything is possible with enough work. A standard gas spring will not just drop in. The B25 and B28 have a latching rod down the center of the piston. They would require a redesign of the piston and trigger assembly.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: pappa on November 17, 2011, 05:18:08 PM
Scotchmo,
Thanks! Now I can stop dreaming about it.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Skjold on November 18, 2011, 07:37:32 AM
What about a Beeman RS2?  I would love one of these in a gas piston.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 18, 2011, 03:34:03 PM
What about a Beeman RS2?  I would love one of these in a gas piston.

Yes, the RS2 should be a fairly simple conversion. The trigger looks very similar to the higher end Tech Force rifles. The trigger latches on the piston skirt so there should be room for a gas spring. No promises - just my observations.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Skjold on November 19, 2011, 02:33:59 AM
I am getting a Beeman RS2 when I return from Afghanistan.  I will be in Maine where is gets pretty cold but would still like to be able to shoot.  I hear the Gas Springs do not suffer from the effects of the cold like wire springs do.  I like the duel caliber option of the RS2 which is why I am getting it. A gas spring would make this a good multipurpose all weather rifle.  Would the "Red" spring give it the same or perhaps a slight bump in power as well?  I know you do not recommend the "yellow" but I would also like to get a slight to moderate increase in power if possible. ;)
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 19, 2011, 03:46:13 AM
I am getting a Beeman RS2 when I return from Afghanistan.  I will be in Maine where is gets pretty cold but would still like to be able to shoot.  I hear the Gas Springs do not suffer from the effects of the cold like wire springs do.  I like the duel caliber option of the RS2 which is why I am getting it. A gas spring would make this a good multipurpose all weather rifle.  Would the "Red" spring give it the same or perhaps a slight bump in power as well?  I know you do not recommend the "yellow" but I would also like to get a slight to moderate increase in power if possible. ;)
The gas springs do change some with temperature (on an absolute scale). When cold, they do lose velocity.  They warm up after just a few cycles. A "dry" wire spring is probably less affected by temperature. But many tuned wire springs use a "heavy tar" lube. I'm guessing that the "heavy tar" is affected by temperature at least as much as the gas spring. I'm not convinced that either has the advantage with temperature variation.

The red spring is probably close to stock. It may be the same or slightly more powerful than the stock spring, but that is just an educated guess.The only way that I could check for sure is if I knew the original RS2 wire spring dimensions and operating parameters - wire diameter, number of coils, outside diameter, free length, installed length, stroke length. From this information, you can calculate the mechanical energy of the spring in ft-lbs. That is then compared to the different gas springs.

I tested a red label gas spring in my TF99 this week. Even after shortening the stroke a little bit, it still  produced about the same velocity as the stock spring. 720fps with CP 14.3gr. The stock spring in the TF99 was unusually long with a lot of preload.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Skjold on November 21, 2011, 03:04:24 AM
I am told the RS2 spring is a .120 wire dia - 11" free length with 44 coils - inside dia .465 outside dia .715.  Would the Gas coversion maintain at least equal power if not increase it a bit?  I am guessing the gas conversion will make it smoother as well and more accurate.

Title: Re: Chinese air rifles and Gas spring conversions
Post by: Dick Tracey on November 21, 2011, 03:22:00 AM
PA is/was offering the gas piston conversion for the dual barrel RS2.  You can order the gun and the conversion ram at the same time and they will do the conversion free and ship to you.  The ram is/was about $100.  They have a silver barrel and receiver optioned model with the better trigger and scope combo that I have fancied from afar for some time now.  Might be a Black Friday purchase if on sale.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 21, 2011, 05:11:31 AM
I am told the RS2 spring is a .120 wire dia - 11" free length with 44 coils - inside dia .465 outside dia .715.  Would the Gas coversion maintain at least equal power if not increase it a bit?  I am guessing the gas conversion will make it smoother as well and more accurate.

I will have to make some assumptions here. We will say 43 active coils since it probably has at least 1/2 of a closed coil on each end. No installed length or stroke length was given so I will just use the maximum deflection and a 4 inch stroke. Your rifle may have a longer stroke but this will at least give a relative comparison. So the decision on which spring to select should still hold.

I calculate that the force will go from 51lbf to 179lbf, or 115lbf average:
115lbf.x4in/12in per ft=38ft-lbs. of mechanical energy

The blue label spring will go from 100lbf to 130lbf, or 115lbf average:
115lbf.x4in/12in per ft=38ft-lbs. of mechanical energy

The red label spring will go from 150lbf to 195lbf, or 173lbf average:
173lbf.x4in/12in per ft=58ft-lbs. of mechanical energy

The wire springs seems a little short on preload for a rifle of that power level. But if the spring dimensions are correct, you can use the blue label gas spring to get approximately the same power as the wire spring. It should be smoother to cock and shoot. The peak force of the red spring is only about 9% greater than the wire spring but stores 50% more energy. So it is probably within safe limits of the rifle. It will be a little harder to cock but should be smoother as far as torque and more powerful. It will kick harder. Double check your wire spring dimensions. The last post mentioned that this rifle is available with a gas spring installed. If you have not already bought the rifle, that may be a good option.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Dick Tracey on November 21, 2011, 08:27:18 AM
I just checked the PA site this morning.  The dual air beemans are still available and so is the gas ram.  You can purchase both together and the ram will be installed and shipped, or you can purchase the gas ram and ship your gun to PA to be installed.  I would recommend calling PA to make sure it will work before ordering.  Also PA will not sell ram without the installation.
https://www.pyramydair.com/product/crosman-nitro-piston-conversion-fits-many-newer-gamo-rifles?a=2103 (https://www.pyramydair.com/product/crosman-nitro-piston-conversion-fits-many-newer-gamo-rifles?a=2103)
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Dick Tracey on November 21, 2011, 04:16:20 PM
OK My bad.  Called PA and was told they do not sell gas pistons for beeman guns.  Specifically asked about the beeman elite dual Caliber rs2.  They do offer for gamo however.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: ray in wi on November 22, 2011, 11:57:39 AM
Fantastic Post!! Thanks for the info
Ray
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Skjold on November 22, 2011, 12:26:50 PM
Where can I buy a red piston for the RS2?  Do you do the conversions?  If so what would you charge?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 22, 2011, 03:26:06 PM
Where can I buy a red piston for the RS2?  Do you do the conversions?  If so what would you charge?
I assume that your asking me. I don't do conversions for others but I think mikeiniawoa does them. I believe he is at Flying Dragon Air Rifles - 515-924-3699

If you do it yourself, you need to measure the exact stroke length of your rifle before you order a gas spring. I gave some sources at the beginning of the thread but you need to know what to order first.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Smackey54 on November 22, 2011, 03:33:28 PM
Where can I buy a red piston for the RS2?  Do you do the conversions?  If so what would you charge?
I assume that your asking me. I don't do conversions for others but I think mikeiniawoa does them. I believe he is at Flying Dragon Air Rifles - 515-924-3699

If you do it yourself, you need to measure the exact stroke length of your rifle before you order a gas spring. I gave some sources at the beginning of the thread but you need to know what to order first.

I looked at McMasters, MSC, and Grainger, but could not find a retailer for the particular  sizes. Should I go to a manufacturer's site and then look for a distributor there?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 22, 2011, 04:30:05 PM
Yes, check with the different manufacturers. Most of them will refer you to a distributor. I posted some information earlier in this thread. N-Forcer will deal direct.

...
So far I'm preferring to use the N-Forcer products. It seems to be a smaller company that is willing to deal directly with end users. Just deal with them in a professional manner and it should go fine. They cost about $45+/- for the airgun sizes and they give a small discount for ordering 10+ of any one item.
...
Title: Re: Chinese air rifles and Gas spring conversions
Post by: D_Weezy on November 29, 2011, 01:22:18 PM
Which one of those gas springs could I use for my B3-1's? My B3's are the old ones, with the white spring guide.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on November 29, 2011, 02:01:30 PM
Which one of those gas springs could I use for my B3-1's? My B3's are the old ones, with the white spring guide.

There are a few critical dimensions that you need to measure in order to make the selection. Start with:

What is the stroke length of the B3-1?
How much space in the B3-1 for a compressed spring?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: D_Weezy on November 29, 2011, 03:09:46 PM
Anyone out there with a B3-1 that has this info needed for a gas ram fit? How do you figure the stroke length of the B3-1 air rifle? Solid length of spring should be (number of coils x wire size = compresed spring length - example/ 36 coils x .117" wire size = 4.212" compresed spring length) These figures are for the B3-1 with standard 9.30" length mainspring.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: YankeeDude on December 16, 2011, 11:00:20 PM

I tested a red label gas spring in my TF99 this week. Even after shortening the stroke a little bit, it still  produced about the same velocity as the stock spring. 720fps with CP 14.3gr. The stock spring in the TF99 was unusually long with a lot of preload.

Speaking of TECH FORCE airguns . . .

What about the TECH FORCE JET ?

Is a gas ram conversion possible on a .22 TF Jet ?

I am interested in a possible velocity increase with heavy .22 pellets 21.1 gr +/- . . . Would like to see 850 + fps. Also, around  950 fps, w / 14.3 CPHP's.

Dave
Title: Re: Chinese air rifles and Gas spring conversions
Post by: blaqheart on January 17, 2012, 08:42:01 AM
hi guys, my air rifle is rated at 1250 fps with the standard spring.  If I install the 19mm x 125mm 150 bar nitro ram from n-forcer what velocity can I expect?   
Title: Re: Chinese air rifles and Gas spring conversions
Post by: z28rod on January 17, 2012, 07:18:55 PM
That 1250 is with pba ammo ill bet, and the rifle looks preaty powerfull now , why would you need more anyways ? What rifle is it ? And caliber ?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: blaqheart on January 17, 2012, 07:55:21 PM
its a hatsan 125 .177.Honestly i am not after more power, i heard the gas ram reduces the recoil so i could squeeze all the accuracy from it. However i would like to maintain its velocity.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: z28rod on January 18, 2012, 07:22:59 AM
From what guys have written here and told me , that n forcer gas spring should make your rifle into a super cannon, but the 22 cals with 14.3 gr pellets are going super sonic so a 177 even with the heaviest pellets would be super sonic all the time , so if sound isnt a issue then your the man but if it is, it will be like your shooting a 22 rimfire all the time in youir backyard ? is that cool ? i would get the red spring not the yellow marked spring, or just one level down from the ones installed in the wfh .22 and .25 cal. rifles, so you can keep her under ss speeds.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: tjk on January 18, 2012, 10:40:47 AM
850 with +/- 21 grain .22 caliber pellets?!?!?! From a bb type rifle??? Thats asking an awful lot. Even if you were to install a ram that could generate the energy to do that, I wonder how long it would be before we hear posts on the Airgun forums of how 'so and so' was seriously injured when the comp-tube walls/retaining pin(s) render and back end of their rifle busts through and causes,..... Sorry to paint such a negative picture, but I just
get a bad feeling about the trend some folks are heading with these 'power' mods. If you need that much power, get a RF or a pcp. Simple as that.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: MarkFive on January 18, 2012, 11:02:30 AM
Here is a rough thought I had on the gas ram conversion subject. If you have an advanced degree in physics please speak up.

The more powerful ram will force the piston to move faster, relative to a "stock" or lesser ram, but only marginally because they both are moving the same volume of air from the compression chamber.

So the best method of increasing performance would not be only a stronger ram, but also more air volume. I believe the NP XL guns are an example of this, but I haven't measured their compression chamber to be sure, only looked at the schematics.

I plan to look for ways to increase volume while converting my gun. I have no idea if it is even possible. Custom parts would obviously be involved, so don't try this at home.

Thoughts?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on January 18, 2012, 04:29:10 PM
MarkFive -
I don't have an advanced degree in physics but I'll speak up anyway. You are correct. The primary limiting factor in piston gun power is the swept volume. The head space also plays a role. Those two factors determine the compression ratio. Knowing those properties makes it possible to determine the maximum possible amount of energy that can be transferred. Adding more spring energy beyond that makes no difference in power output. It just makes the piston slam harder.

Increasing the swept volume returns a proportional increase in power. Increasing the spring energy gives diminishing returns and maxes out at some point.

It is sometimes possible to increase the swept volume by a small amount. A large change requires a redesign of the whole mechanism. But if spring energy is already near the maximum, a small increase in chamber volume can yield a substantial power increase.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Paul68 on January 19, 2012, 10:19:44 PM
"The primary limiting factor in piston gun power is the swept volume."

I keep seeing this said, but something seems like it doesn't add up to me.

In the end, you are transferring energy to the pellet. The spring stores the energy you provide by compressing it, the air is a "vehicle" for transfering that energy from the spring to the pellet, and the pellet then transfers the energy to the barrel, whatever it hits, and to a lesser degree, the atmosphere and losses that get all scientifiky like and stuff.

The problem I have with the idea that chamber volume limits energy is that it doesn't seem that volume alone dictates how efficiently energy is transferred, how much can be stored, or what limits the total transfer of energy. We naturally view air as gaseous and without much energy or resistance, but in a closed system (chamber) applying energy to air causes the air to absorb energy and store it until it is released or transferred. This is how an air compressor works to power tools and the like, which is the same principal for an AG. Putting more energy into the "air", stores more energy until it is released.

For example, if we pump up our air compressor to 250 psi, we have stored a whole bunch of energy, and we can then run an impact wrench for some time as the rate of energy release is controlled and spread out over a long period of time.

Now, if we take that same compressor and simply open a hole in it without any regulation or control over the rate of energy release, we get a catastrophic and extreme release of energy over a short period of time. **Kaboom.** The restricted release of energy over a long period of time results in a little force of long duration, the full release over a short period results in a ginormous force of short duration. The restricted release would simply loosen lug nuts, the full release would blow the wheel off. We are simply altering how the energy is applied.

Also, lest you think that by adding air to the compressor in order to adde energy we are in effect increasing the total "volume" of air, which is also true, consider that this is not the only way to add energy to get the same results. We could also apply heat to air in a closed chamber instead and still store a whole lotta energy.


So, it would seem, that applying more energy to a specific amount of air would result in a cooresponding increase in energy stored in that  air. Put a little energy into a volume of air, get a little out; put a lot of energy into that same volume of air, get a lot out. Of course there are limits and losses due to friction, heat and the like that reduce possible returns, but I think this gets the idea across.

It seems like the main limiting factor below the total limits of how much energy a volume of air can store, would be how efficiently the energy can be transferred to the pellet rather than how much volume there is. Since I doubt that an airgun is capable of containing energies high enough to represent the total storage limits of a volume of air, perhaps something else is causing the poor returns on energy represented by larger springs?

(I think I hurt my brain with this one)

;)
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on January 20, 2012, 01:03:07 AM
You can't compare how a springer works to the energy stored in an air tank.... In a springer, the compression of the air occurs in a fraction of a second and incorporates a large degree of heating.... enough to cause some combustion of the film of lube on the chamber walls according to the Cardew brothers in their work "The Airgun from Trigger to Target".... They proved this by filling and firing a springer in a Nitrogen atmosphere and it lost a lot of power.... when used in air, the power returned....

There is an old saying in automobile engines that "nothing beats cubic inches".... While it's true that you can produce incredible amounts of horsepower from a tiny engine by supercharging it.... if you do the same modifications to a larger engine you get even more power.... If you push any engine far enough you will blow it up.... If you push a springer far enough, you will simpy crash the piston into the end of the chamber and start destroying parts.... Add volume, and you have a larger amount of air to cushion and harness the energy of a larger spring....

Up to a certain level, increasing the spring power will add performance.... Once that level is reached, trying to exceed it only makes the gun harsh shooting and eventually will destroy it....

Bob

Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on January 20, 2012, 02:42:43 AM
Paul68,
We can take a simplified view of it so that it is more clear:

You have a 6 inch long cylinder with a piston inside it. There is 1 inch of head space at the bottom of the stroke. That is a lot but it is just for demonstration. You manually push the piston until it comes to within 2 inches of the bottom, resulting in a 6 inch column of air squeezed into a 2 inch space. It took a certain amount of energy to do that. If you input some additional energy, you can further compress that column of air down to 1 inch. At that point, no more energy can be accepted. The piston is bottomed out and the head space contains all of the compressed air.

If you use a spring to launch that piston down the tube, all of the energy in the spring wants to go somewhere. Once the spring energy is high enough to bottom out the piston, you have reached the limit. Any excess energy just ends up as energy transferred into smashing the seal and jarring the rifle.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: blaqheart on January 20, 2012, 06:31:48 AM
I got a buddy with a rws 48,he put a webley patriot spring in it,he got more power,or so he believes since its never been put trough a crony.The gun is no longer a smooth  shooter and it spends a lot of time in the shop.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: william71743 on January 20, 2012, 01:36:20 PM
All of this is very interesting and all the forces of physics certainly apply . That said, it's PSI, pounds per square inch right, and the base of a pellet isn't very big . I'm sorry I'm brain dead already,  but is it something like .0246 for a .177 cal.  Wouldn't it take a big change to make just a little difference, someone with a degree in physics again ?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Paul68 on January 20, 2012, 11:09:10 PM
Paul68,
We can take a simplified view of it so that it is more clear:

You have a 6 inch long cylinder with a piston inside it. There is 1 inch of head space at the bottom of the stroke. That is a lot but it is just for demonstration. You manually push the piston until it comes to within 2 inches of the bottom, resulting in a 6 inch column of air squeezed into a 2 inch space. It took a certain amount of energy to do that. If you input some additional energy, you can further compress that column of air down to 1 inch. At that point, no more energy can be accepted. The piston is bottomed out and the head space contains all of the compressed air.

If you use a spring to launch that piston down the tube, all of the energy in the spring wants to go somewhere. Once the spring energy is high enough to bottom out the piston, you have reached the limit. Any excess energy just ends up as energy transferred into smashing the seal and jarring the rifle.

Thanks. I hadn't taken into account the need for extra volume to compensate for compression itself. This would explain the ability of PCP's to produce more power, because they aren't limited by a single compression of a small air volume. In other words, we are limited in springers by the PSI that can be produced with a certain volume of air.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on January 20, 2012, 11:30:52 PM
Thanks. I hadn't taken into account the need for extra volume to compensate for compression itself. This would explain the ability of PCP's to produce more power, because they aren't limited by a single compression of a small air volume. In other words, we are limited in springers by the PSI that can be produced with a certain volume of air.
True, and there is a practical limit to the maximum pressure. So once we reach that practical limit, the only way to transfer more energy is to increase the swept volume.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on February 04, 2012, 02:06:43 PM
Could I request that the Admins sticky this thread?.... I for one, don't want to lose it....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Mike 4888blues on February 09, 2012, 06:27:48 PM
 :D yes  I agree this should be saved great discussion 
Title: Re: Chinese air rifles and Gas spring conversions
Post by: peterdulux on February 09, 2012, 11:27:08 PM
Just what I've been looking for too. I just bought a Walther Talon in .25, what a hammer. Took out the cheap scope stop in less than 30 shots.
Three questions for now; Will these pistons fit the Talon and a Diana 350?
How about a little piston for a Diana 24?
Would like a little more punch from my XL1100. It shoots predators very well and would like to get them up to mid 800's. Is that possible?

I'll keep reading, and thanks so much. Complete information is always so refreshing.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Kailua on February 21, 2012, 11:49:22 PM
Scotchmo
I know this is an old thread.  But if you can get back to this.  I read this post and might have missed something.  When looking at the N-forcer pdf the nitrogen springs are pressure adjustable.  Have you tried to adjust the pressure.  Also do you think air can pressurize the cylinder.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on February 22, 2012, 12:59:59 AM
Kailua,
I have not tried to adjust the pressure. I have not needed to yet. I thought about the use of air. It might be OK for experimenting. Even though air is mostly nitrogen, it also contains some oxygen which promotes corrosion and oxidation. So use it at you your own risk. I would stick with pure nitrogen for long term use.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Kailua on February 22, 2012, 01:33:48 AM
The reason why I had asked was the numbers needed for the pressure adjustments were in the PCP range and wondered if a PCP pump or tank could work instead of renting a nitrogen tank for a such a small amount.  Good point on moisture.  May need a good air filter.  Not sure if there is a filter to hold that kind of pressure.  Thanks for the reply.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: SMOKEY on February 23, 2012, 09:57:45 PM
another reason to use only nitrogen is that it dosent expand with heat !
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on February 23, 2012, 10:29:13 PM
another reason to use only nitrogen is that it dosent expand with heat !
Yes it does, just like air.

PV=nRT

Title: Re: Chinese air rifles and Gas spring conversions
Post by: codytwoeyes on March 30, 2012, 12:00:53 AM
You wrote (I tested a red label gas spring in my TF99) have you tried a yellow in a tf 99.
do you think it is OK just to Strong for the 99? can you tell the size me of the ram you ordered.
sorry there is just so much I dont know. is there perhaps a really strong spring that would be better?
I  asking all this because  I now have a 99. nice gun but my XL has just about ruined me.I really like power! I think the 99 can be up power some however I do want to learn to do this the right way.
So any help you would or can give would greatly appreciated.-- I will pass it on   
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on March 30, 2012, 12:28:03 AM
You wrote (I tested a red label gas spring in my TF99) have you tried a yellow in a tf 99.
do you think it is OK just to Strong for the 99? can you tell the size me of the ram you ordered.
sorry there is just so much I dont know. is there perhaps a really strong spring that would be better?
I  asking all this because  I now have a 99. nice gun but my XL has just about ruined me.I really like power! I think the 99 can be up power some however I do want to learn to do this the right way.
So any help you would or can give would greatly appreciated.-- I will pass it on   
What does your TF99 do in stock form?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: brogreg on June 20, 2012, 09:35:52 PM
just wondering if anyone has done a gas piston conversion on a crosman phantom
and if so
what do you see as the pros or cons with this particular gun
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Fwawa20 on June 20, 2012, 10:18:49 PM
You wrote (I tested a red label gas spring in my TF99) have you tried a yellow in a tf 99.
do you think it is OK just to Strong for the 99? can you tell the size me of the ram you ordered.
sorry there is just so much I dont know. is there perhaps a really strong spring that would be better?
I  asking all this because  I now have a 99. nice gun but my XL has just about ruined me.I really like power! I think the 99 can be up power some however I do want to learn to do this the right way.
So any help you would or can give would greatly appreciated.-- I will pass it on   
Yes I was wondering the same thing about my TF99P. It's really accurate already just want to gain a little more power for pushing 18g pellets. This is my primary hunting rifle, and I use it for mostly squirrel,rabbit,possums,coon, and g-hogs(TANKS).
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on June 20, 2012, 11:28:01 PM
You wrote (I tested a red label gas spring in my TF99) have you tried a yellow in a tf 99.
do you think it is OK just to Strong for the 99? can you tell the size me of the ram you ordered.
sorry there is just so much I dont know. is there perhaps a really strong spring that would be better?
I  asking all this because  I now have a 99. nice gun but my XL has just about ruined me.I really like power! I think the 99 can be up power some however I do want to learn to do this the right way.
So any help you would or can give would greatly appreciated.-- I will pass it on   
Yes I was wondering the same thing about my TF99P. It's really accurate already just want to gain a little more power for pushing 18g pellets. This is my primary hunting rifle, and I use it for mostly squirrel,rabbit,possums,coon, and g-hogs(TANKS).
Had this question earlier. I can't say if it will give you more power unless you tell me what your FPE is right now. What velocity are you shooting the 18gr already.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: gamo2hammerli on June 20, 2012, 11:58:25 PM
Hey brogreg....first off, welcome to the GTA forum and family.  Check out some of these links:

http://www.gatewaytoairguns.org/GTA/index.php/topic,13374.0.html (http://www.gatewaytoairguns.org/GTA/index.php/topic,13374.0.html)

http://www.gatewaytoairguns.org/GTA/index.php/topic,18220.0.html (http://www.gatewaytoairguns.org/GTA/index.php/topic,18220.0.html)
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Fwawa20 on June 21, 2012, 08:45:47 AM
No chrony but if I had to guess from reading others numbers I would say its shooting them 640-650fps
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on June 21, 2012, 02:27:05 PM
No chrony but if I had to guess from reading others numbers I would say its shooting them 640-650fps
Without a chrony, there is no way of knowing what you really have or end up with as far as FPS or FPE. So I would just go for the best feeling shooter. Put in a 100mm red label spring and shim the piston head to reduce the stroke down to 94-96mm. You'll shoot about the same velocity (you won't know without a chrony so what does it matter). But you'll get a better shot cycle. Less recoil, no twang, no torque.

Forget the yellow label spring. The TF99 trigger is already marginal. The extra force of the yellow will also make cocking and shooting unpleasant. The yellow may be suitable for a rifle with a piston diameter of 28-32mm, but for a 25mm piston, stick with the red or blue label gas spring.
Title: Converted my TF87 to gas spring
Post by: Scotchmo on August 08, 2012, 04:35:45 PM
I got a good deal on a .177 TF87 from Pyramyd Air a while back and finally got around to doing the conversion to a gas spring.

The TF87 has about a 107mm stroke (110mm when cocked to bottom). The closest stroke in a standard gas spring is 100mm or 125mm. The gas spring needs to have a stroke that is at least 4 or 5mm longer than the rifle stroke. If I shortened the stroke of the TF87 to below 100mm, I could use a 100mm spring but than it would end up the same power as a TF99. That would be OK but it would not fully utilize the swept volume of the TF87. After some careful measurements, I determined that I could fit a 125mm gas spring. I would need to drill out a little material from behind the piston head in order to get another 1/4 inch or so of space, otherwise the spring would have too much preload and would bottom out.

I already had an N-Forcer MF19-125-RD on hand so I did the minor modification to the TF87 piston and machined a centering spacer for the gas spring body. The gas spring was installed "frontwards" with the rod pointing toward the front. That direction was the easiest to implement on the TF87.

Testing showed that I was matching the wire spring FPE with 10.5gr pellets going about 890-900fps. I then trued up the piston and made an aluminum piston head with a PTFE piston ring. I'm now getting about 920-930fps with the 10.3gr and 10.5gr pellets.

It is a smooth shooter right at 20fpe.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Deej on August 13, 2012, 04:34:56 PM
Thanks,saved me a lot of research.have been pondering converting my QB 57,and you practically did my homework for me.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: brogreg on August 13, 2012, 09:12:57 PM
not all gas springs are equal
i have been doing as much research as i can on this subject
i have spent some time visiting a local nitrogen spring manufacturer
now that i've found this local shop i've been putting them on everything
the internal valving and oil weight in them makes a huge difference in the speed the spring releases it's energy no matter what the psi
the shop is a satellite shop of one in denmark but they will have all there equipment by the end of sept to custom build there own
i've talked to the owner and he is interested in trying out a few things to make a spring for my hatsan 60s
his springs have a release mechanism to release pressure with a $10 dollar tool and if too much nitrogen is released he will re-fill them for free 
i just had one filled for the 3rd time today (think i have it dialed in now )
these are a quality product and at $20 canadian for a gas spring
you can't go wrong

fairly new here so is  it ok to post a link to there website

Title: Re: Chinese air rifles and Gas spring conversions
Post by: brogreg on August 13, 2012, 09:29:47 PM
Hey brogreg....first off, welcome to the GTA forum and family.  Check out some of these links:

http://www.gatewaytoairguns.org/GTA/index.php/topic,13374.0.html (http://www.gatewaytoairguns.org/GTA/index.php/topic,13374.0.html)

http://www.gatewaytoairguns.org/GTA/index.php/topic,18220.0.html (http://www.gatewaytoairguns.org/GTA/index.php/topic,18220.0.html)
thanks for the links
i finally made my choice after alot of reviews and for the most bang for the buck i went with the hatsan 60s with the quattro trigger and sas in a .22 cal
Title: Re: Chinese air rifles and Gas spring conversions
Post by: ako on August 13, 2012, 10:11:23 PM
Scotchmo
I know this is an old thread.  But if you can get back to this.  I read this post and might have missed something.  When looking at the N-forcer pdf the nitrogen springs are pressure adjustable.  Have you tried to adjust the pressure.  Also do you think air can pressurize the cylinder.

Kailua, I was thinking you could go to the nearest off road (4x4) shop. They use nitrogen shocks and bumpstops in the long travel suspension set ups. Would take them about 2s to fill a tiny little cylinder we are taking about. Then you can play around with any pressure you feel like.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: brogreg on August 14, 2012, 05:03:58 AM
the cylinder should be emptied before re-filling to get a proper and accurate pressure if the pressure is taken to low.
adjusting the pressure is strictly letting out some gas through the fill valve
let out to much and your back to square one
these springs are a completely different animal than gas shocks
to increase spring speed the valve can be drilled out about .5mm
the gas spring force is measured during filling not by the bottle pressure but by spring force as the tube is filled

there isn't an actual adjustment
 i have adjustable gas reservoir shocks on my truck
and the valving dampens the speed not the overall pressure
slowing them down is the easy part

100 psi through a 1 inch hole or 200 psi through a pin hole
what would cause the most damage
And why am i still awake at 1 am on a tuesday
i wonder if this will make any sense to me in the morning
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on August 14, 2012, 02:29:46 PM
...these springs are a completely different animal than gas shocks
to increase spring speed the valve can be drilled out about .5mm
the gas spring force is measured during filling not by the bottle pressure but by spring force as the tube is filled ...

I don't know which springs you are talking about. None of the die springs that I listed have any internal valves. There is nothing that can be drilled out.

You can measure the force after filling to a safe specified pressure.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Paul68 on August 14, 2012, 02:45:58 PM
I know that some manufacturers offer rebuilable gas springs than can be broken down and resealed. Perhaps he is dealing with something along those lines Scotchmo.Those can be broken down and messed with internally, though it seems to me a lot of extra hassle when you can instead get a spring with the desired rate already set.

Most of the springs available list their rates as well as force, and I belive the die type springs usually referred to here are generally intended to replace or fill the same role as coil springs, so rates are similar if not equal or better.

I'm almost to the point where I can order a few different gas springs and try em out. I'll definitely be using your efforts as a guideline Scotchmo.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on August 14, 2012, 03:03:01 PM
I know that some manufacturers offer rebuilable gas springs than can be broken down and resealed. Perhaps he is dealing with something along those lines Scotchmo.Those can be broken down and messed with internally, though it seems to me a lot of extra hassle when you can instead get a spring with the desired rate already set. ...
The N-Forcer gas springs can be broken down and resealed. They have no valving. There is nothing that can be drilled out to speed up the spring. The only adjustment is the pressure. I'm guessing that he is dealing with some kind of gas lift spring with a regulated rate of return. I guess you could get them to work by drilling out the valving so that they would be fast enough to work in an airgun. But if you stick with die springs, you don't have to.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: brogreg on August 14, 2012, 09:57:44 PM
I know that some manufacturers offer rebuilable gas springs than can be broken down and resealed. Perhaps he is dealing with something along those lines Scotchmo.Those can be broken down and messed with internally, though it seems to me a lot of extra hassle when you can instead get a spring with the desired rate already set. ...
The N-Forcer gas springs can be broken down and resealed. They have no valving. There is nothing that can be drilled out to speed up the spring. The only adjustment is the pressure. I'm guessing that he is dealing with some kind of gas lift spring with a regulated rate of return. I guess you could get them to work by drilling out the valving so that they would be fast enough to work in an airgun. But if you stick with die springs, you don't have to.
no guess work involved these are a direct replacement for coil springs that operate at equal or greater speed than a coil
and not a dampened lift spring

how are the n-force lubricated
oil or grease
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on August 15, 2012, 12:34:18 AM
brogreg,

The N-Forcer has an oil packed area between the pressure seal and the shaft wiper. Some brands do not. The oil can be a problem when your trying to eliminate all combustion products from a spring gun. Small amounts can be drawn out when the spring extends and it will eventually migrate into the compression cylinder.

The springs that you are describing may be different than what we are talking about.

What is the brand? Do you have any specifications? What are those specs? Do you have any web page links to them?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: elite_airguns on December 19, 2012, 12:14:27 PM
GAS RAM ELITE AIRGUNS can be used in some chinese like BAM and our kit can be used to.



DOUGLAS

ELITE AIRGUNS
Title: Re: Chinese air rifles and Gas spring conversions
Post by: venxxxxx on February 25, 2013, 05:01:18 PM
WHere can I get a hold of a crosman gas ram for a conversion? Searched and no sites listed. Called crosman? I'd prefer on a website thanks
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Paul68 on February 25, 2013, 07:26:17 PM
Go to Crosmans website, and in the lower right corner you will see a link to manuals/parts diagrams. Use those schematics to find the part and part# you want, then just call Crosman and order it.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: brogreg on March 14, 2013, 09:17:33 PM
brogreg,

The N-Forcer has an oil packed area between the pressure seal and the shaft wiper. Some brands do not. The oil can be a problem when your trying to eliminate all combustion products from a spring gun. Small amounts can be drawn out when the spring extends and it will eventually migrate into the compression cylinder.

The springs that you are describing may be different than what we are talking about.

What is the brand? Do you have any specifications? What are those specs? Do you have any web page links to them?
better late than never
http://www.geminigassprings.com/index.php?page=shop.product_details&flypage=flypage1.tpl&product_id=1734&category_id=113&option=com_virtuemart&Itemid=12 (http://www.geminigassprings.com/index.php?page=shop.product_details&flypage=flypage1.tpl&product_id=1734&category_id=113&option=com_virtuemart&Itemid=12)
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on March 15, 2013, 12:21:40 AM
Those springs appear to come standard with damping:

http://www.geminigassprings.com/index.php?option=com_virtuemart&page=shop.browse&category_id=113&Itemid=12 (http://www.geminigassprings.com/index.php?option=com_virtuemart&page=shop.browse&category_id=113&Itemid=12)

It is a lift spring. It won't work as an airgun spring with damping. Some companies may allow special orders without damping in which case it might work. 19mm die springs typically have no damping and work well as airgun springs.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Phoghat on August 24, 2013, 04:40:37 AM
" Gas springs have some advantages over wire springs. I like them a lot so far. But they are not a cure all. Sometimes wire springs are more appropriate."
For the non-experienced ( like me ) when would a wire spring be more appropriate? Also, I have heard that nitro-pistons have been prone to leakage, any thoughts on that?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: svhanc on August 24, 2013, 07:54:49 AM
I got my 19x080 red N-Forcer spring and it went together easily in my QB57.  The N-Forcer people are nice and have really quick shipping.

As installed, I put a spacer between the body and piston to get to basically zero preload rather than a gap.  Is there a rule of thumb on gas springs?  There is a clunk each cycle, so I think it needs a little extra spacing but it would be nice to just go back in once.

It is smoking a little out of the barrel and dieseling, so I am doing a round of goo gone.  It wasn't doing it before, so I suspect I picked up a few fps. 

The shot cycle is a lot calmer, so if it ever stops raining here I will see if I improved accuracy.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on August 24, 2013, 02:05:56 PM
I'm finally getting around to acquiring the gun to go with my Red N-Forcer 19 x 100 gas spring.... It's a Crosman Phantom in .22 cal, and I have a long piston from one of the Canadian detuned models where they reduce the stroke from 100mm to about 50mm to keep the gun under 500 fps.... The plan is to shorten the piston and cut a new sear window in it to set the stroke at just under 100mm.... My question is this.... What is the longest stroke I can use with that gas spring?.... 95mm?.... 97mm?....99mm?.... Scotchmo ????

Also, what is your current thinking about which way to install the piston, with the piston rod forward, or the outer housing forward (more travelling mass) ???.... How much preload do I need (I assume that robs stroke?)....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: TleVta on August 24, 2013, 02:10:45 PM
Mind if I ask how much the Red N-Forcer spring costs?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on August 24, 2013, 03:01:53 PM
Can't remember, I got it a year ago.... $40 plus shipping?....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: TleVta on August 24, 2013, 04:19:13 PM
Close enough. Thanks Bob.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: OleTomCat on August 24, 2013, 06:34:46 PM
They are 49.96 + shipping, so a little over $50.00....
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on August 25, 2013, 10:24:58 PM
I got my 19x080 red N-Forcer spring and it went together easily in my QB57.  The N-Forcer people are nice and have really quick shipping.

As installed, I put a spacer between the body and piston to get to basically zero preload rather than a gap.  Is there a rule of thumb on gas springs?  There is a clunk each cycle, so I think it needs a little extra spacing but it would be nice to just go back in once.

It is smoking a little out of the barrel and dieseling, so I am doing a round of goo gone.  It wasn't doing it before, so I suspect I picked up a few fps. 

The shot cycle is a lot calmer, so if it ever stops raining here I will see if I improved accuracy.
You should not let them top out when operating. Best to leave about about 5% of preload when fully extended. I have used less preload but it can give it more opportunity to squeeze out some of the lube inside the high pressure cylinder. Also don't bottom it out when you compress it as this would tend to move more of the lube in front of the stop piston. I recently found out that it has more fluid in there than I first thought. Even with a conservative stroke length, some fluid can weep out.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on August 25, 2013, 11:34:33 PM
" Gas springs have some advantages over wire springs. I like them a lot so far. But they are not a cure all. Sometimes wire springs are more appropriate."
For the non-experienced ( like me ) when would a wire spring be more appropriate? Also, I have heard that nitro-pistons have been prone to leakage, any thoughts on that?
One thing to consider: the force of a gas spring can vary a significant amount when the temperature changes. Not really a problem in most instances. But say you are shooting a long field target match. I have seen gun temperatures vary 50 degrees F during a match. Velocity and POI can change a noticeable amount. In a situation like that, wire springs can be more consistent.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: OleTomCat on August 26, 2013, 12:52:43 AM
I'm finally getting around to acquiring the gun to go with my Red N-Forcer 19 x 100 gas spring.... It's a Crosman Phantom in .22 cal, and I have a long piston from one of the Canadian detuned models where they reduce the stroke from 100mm to about 50mm to keep the gun under 500 fps.... The plan is to shorten the piston and cut a new sear window in it to set the stroke at just under 100mm.... My question is this.... What is the longest stroke I can use with that gas spring?.... 95mm?.... 97mm?....99mm?.... Scotchmo ????

Also, what is your current thinking about which way to install the piston, with the piston rod forward, or the outer housing forward (more travelling mass) ???.... How much preload do I need (I assume that robs stroke?)....

Bob

Bob,

The N-Forcer Mini Forcers go up to 125mm long in the 19mm ram, the 25mm ram can be made a longer....

I will be converting a Big Cat to a MF19-125-Red with the rod forward...
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on August 26, 2013, 01:31:14 AM
I'm finally getting around to acquiring the gun to go with my Red N-Forcer 19 x 100 gas spring.... It's a Crosman Phantom in .22 cal, and I have a long piston from one of the Canadian detuned models where they reduce the stroke from 100mm to about 50mm to keep the gun under 500 fps.... The plan is to shorten the piston and cut a new sear window in it to set the stroke at just under 100mm.... My question is this.... What is the longest stroke I can use with that gas spring?.... 95mm?.... 97mm?....99mm?.... Scotchmo ????

Also, what is your current thinking about which way to install the piston, with the piston rod forward, or the outer housing forward (more travelling mass) ???.... How much preload do I need (I assume that robs stroke?)....

Bob
The safest would be 90mm total stroke. I personally would not go longer than 96mm (2mm preload and 2mm before bottoming). I did a rifle that was originally 100mm stroke. Using that same gas spring as you, I spaced the head for a 95mm (2.5mm leeway each end) stroke.

Whatever stroke length that you don't use, space the spring so that you divide the unused portion of the stroke between compressed and extended. In other words, a 100mm gas spring is best run between 5mm and 95mm positions (or 2mm and 98mm if you want to push it).

You can run the gas spring either direction. I usually run it body forward. It can then be fit snug in the piston if you want to. And you don't have to use so much extra piston weight.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on August 26, 2013, 01:35:35 AM
Exactly the information I wanted.... I'll likely use about 3mm each end and body forward.... ie 94mm stroke.... Thanks....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Phoghat on September 04, 2013, 06:28:50 AM
Liked your post, very informative. Since I am in Mexico, thinking of importing some China guns, and doing some improvements. Have book marked your info. Thanks again-
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on September 04, 2013, 12:54:16 PM
I have a feeling that the 125mm N-Forcer won't fit in a B-18/19 action.... but that's just a gut feeling.... Perhaps a custom ram with a 100mm body and a 125mm ram might fit if the full 125 won't?.... Scotchmo, do you know?....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Paul68 on September 04, 2013, 02:54:38 PM
The B18/19 takes a 100mm. Why not just use a 100mm and space it a little to give preload?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on September 04, 2013, 03:28:16 PM
I have a feeling that the 125mm N-Forcer won't fit in a B-18/19 action.... but that's just a gut feeling.... Perhaps a custom ram with a 100mm body and a 125mm ram might fit if the full 125 won't?.... Scotchmo, do you know?....

Bob
I'm not familiar with the space avaialable in a B18/B19.

If it has at least 270mm of space for the installed gas spring, go with the 125mm stroke unit. Space it to run at 100mm+ for the stroke.

Otherwise use the 100mm stroke unit and space it to run at a 90 to 94mm stroke. You will still need about 240mm of space for installation.

Modifications to the piston can often allow for more spring space and/or longer stroke.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on September 04, 2013, 04:07:51 PM
Quote
The B18/19 takes a 100mm. Why not just use a 100mm and space it a little to give preload?

I may understand how you can use a 100mm gas ram better in a rifle that is normally 100mm stroke once I get the gun in my hands and look at it.... My plan is to move the sear notch in the piston to achieve the 94mm stroke....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on September 04, 2013, 05:39:14 PM
Quote
The B18/19 takes a 100mm. Why not just use a 100mm and space it a little to give preload?

I may understand how you can use a 100mm gas ram better in a rifle that is normally 100mm stroke once I get the gun in my hands and look at it.... My plan is to move the sear notch in the piston to achieve the 94mm stroke....

Bob

I have found that it is easier to increase the length of the piston head a little rather than increase the length of the piston tail. The Chinese piston guns that I have used have always been from the SAG factory and they have a screw on piston seal. That makes it easy to space for increased piston length. Remember - if you increase the piston head thickness by 6mm, you have reduced the stroke by 6mm. For any given gun: longer piston = shorter stroke.

If you have a lathe, you can make a new piston head. Cut the old one off and braze the new one in place. While your at it, you might want to machine it to use an o-ring rather than the parachute seal.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on September 04, 2013, 10:53:28 PM
I have some "detuned" pistons sitting here that are 50mm longer than stock as the Canadian versions have only a 50mm stroke.... Therefore, it is a simple matter to shorten the tail of the piston and cut a new sear window.... I'll just be increasing the stroke to 94mm instead of 100....

Good point about making a new piston head, though.... I have two pistons here, may do that with one of them, and O-ring it at the same time....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on September 06, 2013, 04:00:09 PM
rsterne,
The sear "window" is hardened so take appropriate steps when modifying that area.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on October 15, 2013, 02:16:18 PM
Scotchmo....

I am about to start on converting my Phantom to an N-Forcer Red 19 x 100 gas ram.... Based on your suggestions, I plan on putting the body of the ram forward, and using a new piston face with O-ring seal.... using the extended face to shorter the stroke to about 96mm.... I would like to be able to shoot 16 gr. Predators at between 670 - 750 fps (16 - 20 FPE), obviously the more the merrier.... If anything, I would like to favour heavier pellets rather than light ones, at least that is my current line of thinking.... However, the gun may have other ideas about what it likes....

Any thoughts or suggestions on how to optimize this gun along those lines.... or if you think another course of action would be better.... would be much appreciated....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on October 16, 2013, 03:40:20 PM
Scotchmo....

I am about to start on converting my Phantom to an N-Forcer Red 19 x 100 gas ram.... Based on your suggestions, I plan on putting the body of the ram forward, and using a new piston face with O-ring seal.... using the extended face to shorter the stroke to about 96mm.... I would like to be able to shoot 16 gr. Predators at between 670 - 750 fps (16 - 20 FPE), obviously the more the merrier.... If anything, I would like to favour heavier pellets rather than light ones, at least that is my current line of thinking.... However, the gun may have other ideas about what it likes....

Any thoughts or suggestions on how to optimize this gun along those lines.... or if you think another course of action would be better.... would be much appreciated....

Bob
If possible, leave room in front of the body to add piston weight if needed. Maybe try it with a hollow aluminum weight/spacer first using your 16gr pellets. Shoot it for awhile. Bump up the piston weight and see if the velocity increases. You should be able to get about 17fpe with that configuration.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: robert w on October 25, 2013, 07:10:23 PM
a gamo is the easiest to convert to gas ram. I converted my big cat and all it takes is a different end plug and a drilled slug that goes over the piston ram. trick is to shim the ram to where it has a preload and its about 5/16th" from going all the way in where the lock pin goes. a compressor is needed . if you put it in with too light a preload, it will break the ring that holds the ram inside the ram body . I know this as it was a lesson learned the hard way
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on December 19, 2013, 09:34:14 PM
Well, I FINALLY got around to pulling my brand new Phantom apart and installing the N-Forcer Red 19 x 100 mm gas spring.... Now bear in mind I never shot this gun before I took it apart, because it was a non-PAL (under 500 fps) version.... I have my PAL so that didn't concern me, and I'm glad I took it apart because there was swarf everywhere, including imbedded in the face of the piston seal.... Everything I had planned pretty much went out the window, however.... First of all, I couldn't install the ram with the body forward, it would have hit the trigger and/or rear spacer when cocked.... I wanted to set the gun up with a 95mm stroke to allow movement at both ends of the stroke, so I shortened an old Canadian "short stroke, 500 fps" piston, leaving the stroke 5mm shorter than the stock one, which I measured at 100mm.... I made a brass button the ID of the piston and with a shouldered hole to fit the end of the ram, that only took up 1mm of room and didn't hit the seal on the end of the ram.... I shortened the rear spacer and spring guide, boring the spacer out to fit the OD of the ram, and set the preload to 2.5mm.... While I had the gun apart I honed the cylinder lightly and carefully deburred the edges of all the holes and slots to make sure nothing would cut the seal.... I used a thin film of Silicone "SuperLube" as suggested by CDT, lightly lubricated the outside of the piston with Honda Moly Paste, and put a dab around the back of the piston seal and reassembled the gun.... I also removed the bear-trap mechanism, as I like to be able to uncock the gun by holding the barrel and pulling the trigger, which the "anti-bear-trap" device prevents, of course....

I ran some patches through the barrel to clean it, set up the Chrony, and started shooting.... This is not my first Phantom, so I had a pretty good idea what to expect, about 15 FPE in .22 cal with a stock spring.... Obviously, I was hoping for that or a bit more, and a smoother shot cycle from the gas ram.... Well, I got the shot cycle I wanted, but not the power.... The gun delivers a nice quiet THUNK, but it only shoots 13-14 FPE.... I'm down about 50 fps with 14.3 gr. pellets compared to a stock Phantom.... The initial part of the cocking cycle is quite a bit harder than what I remember for a Phantom, probably about the same fully cocked, but it's hard to remember exactly, it was 5 years ago.... I must say, though, that this is the smoothest, quietest shot cycle I've ever had in a springer.... I'll throw a scope on it tomorrow and find out how accurate it is....

Scotchmo, if you have any ideas about the lack of power,  I'd like to hear them....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: OleTomCat on December 19, 2013, 10:20:29 PM
Bob,

You may want to try it with the ram flipped around the other way, I had positive results with the Big Cat .177 and an N-Forcer MF19-125-Red with the body forward and heavy pellets, 14.5~15fpe, but with the light pellets and the ram forward it was just 12fpe..

Since you are using lighter pellets for the .22 you may get better results with the ram forward or go to heavier pellets.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on December 20, 2013, 12:46:59 AM
Well I managed to figure out how to turn the ram around.... I had to make a new rear block that allows the body of the ram to move up inside it during cocking and provide a seat for the rod of the ram at the same time.... Anyway, I picked up 0.7 - 1.0 FPE, with the heavier pellets gaining more.... It now shoots the 18.1 gr. JSBs at 595 fps (14.2 FPE).... With 14.3 gr. Express it shoots 655 fps, my old gun did 680.... The recoil is noticable more with the ram body forward, although the shot cycle is still a nice dull THUNK....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on December 21, 2013, 11:43:38 PM
After a LOT more shooting the gun has settled down (actually lost a bit of power, so back to the power it was initially with the shaft forward, even though the body of the ram is inside the piston now) so I did a lot of testing today, going though 32 different pellets, from 11.9 gr. to 25.3 gr. (EunJins won't fit in the breech).... With the lightest and heaviest pellets the gun shoots under 13 FPE, with most in the 14.3 - 15.0 range it shoots over 14 FPE with a few exceptions, and the rest are between 13-14 FPE.... The highest FPE was with RWS SuperDomes (14.9), which tend to be larger and harder, and for any given weight range the lowest was the JSBs, which are very soft.... I suspect that they are starting to move sooner, so the pressure peak is lower.... The gun performs virtually exactly the same as my B-26, right down to not driving JSBs as fast.... It is still about 0.8 FPE less than my stock Phantom from 5 years ago, however.... In addition, the gun with the N-Forcer Red gas ram is about twice as hard to cock as the B-26, but MAN does it have a nice THUD instead of a twangy, lasting vibration.... The trigger, by comparison to the B-26 (with it's REKORD clone) is kind of a joke (can you spell C-R-E-E-P) , although I know it can be drastically improved with an aftermarket replacement....

I had two pellets, which were way more accurate than the rest, the 15.9 gr. JSB Exact and the 16.2 gr. Predators, they both consistently stacked 5 shots into a single hole at 20' while Chrony testing.... Otherwise, about 40% of the pellets I tested were decent (ragged hole), 20% horrible (few shots touching), and the other 40% just so-so.... The "best of the rest" after the Exacts and Preds were the RWS SuperDome and Super H-Point, and the H&N FTTs, the JSB Heavy, Crowman Premiers (boxed), Benjamin HPs, and the H&N Hunter Extreme.... All of those had higher FPE (14.5-14.9 FPE) than the Exacts & Preds, at least at the muzzle.... I was using my roller rest for the forearm, and barely supporting the rifle under the butt, light against the shoulder, and minimum contact with the trigger hand, so the gun was pretty much free to rock and roll as it pleased.... All in all I'm not displeased with the result....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: lillysdad621 on December 22, 2013, 12:06:56 AM
have u tried sizing down the seal? maybe is too tight and is robbing you of some power.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on December 22, 2013, 12:38:05 AM
No I haven't.... it certainly doesn't seem all that tight when I assembled the gun, no forcing required, just a nice sliding fit.... It's a stock Crosman seal, never fired in fact before I took the gun apart to do the conversion.... I'm glad I didn't fire it, because there was a LOT of swarf inside the gun, including imbedded in the face of the seal.... Once the grit was carefully removed, the seal looked good, however, so I reused it.... It was, after all, new.... The chamber was cross-hatched lightly and thoroughly deburred and cleaned....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 56S on December 22, 2013, 12:49:24 PM
Would it have been possible to use the Crosman gas ram?  These can be used in a gun with 100mm of stroke.  The price is right too.  $30.00 delivered.  I have one coming for my XS46U and plan to install it body forward.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Paul68 on December 22, 2013, 07:04:28 PM
Sounds like you might have lost a tiny bit of stroke when you made your piston mods. Otherwise, sounds like a solid shooter.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on December 23, 2013, 12:12:08 PM
Yes, that's exactly the problem.... Trying to install a 100 mm stroke ram in a 100mm stroke gun tends to do that!.... I had to reduce the stroke to 95mm, as per Scotchmo's advice....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: OleTomCat on December 23, 2013, 01:01:24 PM
I had to remove some material so that I can use a 125mm stroke ram in the Gamos that I converted....
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 56S on December 25, 2013, 12:12:57 PM
The Crosman ram came yesterday and while the gals are cooking I'm installing the ram in the 46U.  The new ram has a 4mm threaded hole at the base and that makes for a convienent centering post.  I cut down a 4mm screw to length and turned the outer diameter of the pan head to .250"  Some loctite and it's in.  Inside the piston there is a very short spring guide where I drilled a shallow 1/4" hole to accept the screw head on the base of the ram.  I need to make a spacer for the rear as of right now I am 3mm too short before the preload.  I'm planning to make a 1/4" steel spacer with a very shallow tapered 3/8" hole to center the piston.  I'm hoping this all works since the ram body is about .030" less in diameter than the spring.

Dan
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 56S on December 25, 2013, 03:52:23 PM
She shoots!  Gas ram installed backwards with 5mm preload.  My shop is unheated and with 22 degrees, I didn't expect much from the chrony.  First shot gave me 750 FPS with the 14.3gr CPHP.  Rifle is doing the same thing as me right now; sitting by the fire getting warm.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on December 25, 2013, 05:09:43 PM
I had 750ish with the first shot as well.... then 700, 650 as it settled down and stopped dieseling over the first dozen shots....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 56S on December 25, 2013, 05:33:03 PM
I had 750ish with the first shot as well.... then 700, 650 as it settled down and stopped dieseling over the first dozen shots....

Bob
I usually see little  to no apparent dieseling after reassembly with the dry moly burnish and a very thin rubbed in coat of the Honda 60 mixed with the moly powder.  I end up with more on my finger tips than on the piston.  At least I had no smoke after the shot. 
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on December 25, 2013, 05:42:59 PM
I had no smoke either, but the velocity took a few shots to settle down....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 56S on December 25, 2013, 10:53:22 PM
I got in 20 or so shots before dark and I can say three things with certainty:  It is harder to cock, the accuracy seems to be no worse and the pellet is now spit out like a high speed watermellon seed instead of being thrashed, bashed, twanged and coaxed down the barrel like the spring tended to do.  It sounds more like my Benji 397 than a springer's supposed to.
If I get home from work tomorrow at a decent hour I'll spit some wattermellon seeds over the chrony.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 56S on December 26, 2013, 05:27:39 PM
Not so good news to report.  10 shots, the lowest being 721 and the highest 755.  For the extra effort required to get such a small increase in energy just isn't worth it to me.  Back to the spring when I get a new spring guide from Mike.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: OleTomCat on December 26, 2013, 05:32:54 PM
Not so good news to report.  10 shots, the lowest being 721 and the highest 755.  For the extra effort required to get such a small increase in energy just isn't worth it to me.  Back to the spring when I get a new spring guide from Mike.

That is typical of what I see with Gas rams, they shoot smoother but at a only a minor gain to slight loss in power.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 56S on December 26, 2013, 06:29:39 PM
Not so good news to report.  10 shots, the lowest being 721 and the highest 755.  For the extra effort required to get such a small increase in energy just isn't worth it to me.  Back to the spring when I get a new spring guide from Mike.

That is typical of what I see with Gas rams, they shoot smoother but at a only a minor gain to slight loss in power.
And a large ( in my case ) increase in effort.  I might just try changing it to piston forward to see how it acts.  Regardless, a new spring guide is ordered from Flying  Dragon to convert it back to spring.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: rsterne on December 26, 2013, 09:12:56 PM
I would estimate the cocking effort of my gun roughly doubled during the first part of the stroke, but was only a bit more when almost fully cocked....

Bob
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on December 26, 2013, 10:50:37 PM
Not so good news to report.  10 shots, the lowest being 721 and the highest 755.  For the extra effort required to get such a small increase in energy just isn't worth it to me.  Back to the spring when I get a new spring guide from Mike.

That is typical of what I see with Gas rams, they shoot smoother but at a only a minor gain to slight loss in power.
And a large ( in my case ) increase in effort.  I might just try changing it to piston forward to see how it acts.  Regardless, a new spring guide is ordered from Flying  Dragon to convert it back to spring.
If you are running it with the shaft forward, you will probably need a couple of ounces of extra piston weight. Or you could try some lighter weight pellets. Even with the body forward, extra weight is often needed when you are trying to maximize the FPE.

Since the power of a piston gun is limited by it's swept volume, you are not likely to get a significant power increase by simply changing the spring. If it was undersprung to begin with - maybe.

The gas spring is best used to improve the firing cycle of a rifle. Also, a quality gas spring can far outlast a typical wire spring. But they have their own issues. I did a lot of work with gas spring guns in 2012. I am experimenting with wire spring piston guns right now in order to learn more about them.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: 56S on December 31, 2013, 01:15:37 PM
Not so good news to report.  10 shots, the lowest being 721 and the highest 755.  For the extra effort required to get such a small increase in energy just isn't worth it to me.  Back to the spring when I get a new spring guide from Mike.
New spring guide came in record time and the 46U is back to a much more docile & accurate spring  shooter.  The springer is shooting at a consistant 715-720 FPS at 24 deg with the CPHP 14.3gr.

For some tastes the gas ram may be the way to go.  I'm getting too old and joints ache easily so the spring works best for me.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: JimLC on February 16, 2014, 03:45:54 AM
I'd like to convert my old B-3 to gas. Good info here, but it may be over my head till I learn more. Thats part of the fun!
Title: Re: Chinese air rifles and Gas spring conversions
Post by: OleTomCat on February 16, 2014, 08:00:10 PM
I'd like to convert my old B-3 to gas. Good info here, but it may be over my head till I learn more. Thats part of the fun!

Let me know when you are ready I can walk you through it.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Timtiminy on August 03, 2014, 08:26:24 PM
I tried searching for any Stoeger X20 conversions. I just ordered a X20S and thought it would be cool to convert it to a gas spring. I did see that Stoeger has the ATAC which is basically the X20S with a different stock and  a Gas Spring. I was thinking that I could just use the ATAC parts on the X20S but Stoeger only has the X20S part schematic/ exploded view up on their website. Until the ATAC parts schematic is available I wont be able to see if the parts are interchangeable. What do you all think? is there a better option already out there?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: BowerR64 on December 08, 2015, 02:56:52 AM
Did all this stall out?

Ide like to convert a B3 also but i just want to keep it about the same FPS not really turn it into a magnum just make it smoother cocking and more consistant.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: hookedonpcp on July 11, 2016, 02:16:15 PM
Thanks for all of the info guys
Title: Re: Chinese air rifles and Gas spring conversions
Post by: jjpeters4 on December 01, 2016, 07:18:56 PM
Is there a more powerful ram that can be installed into an npxl?
Title: Re: Chinese air rifles and Gas spring conversions
Post by: JohnInFbg on October 13, 2018, 12:32:25 PM
I had seen a lot of posts on converting a Browning Leverage (exact same rifle as Xisico XS46U) from spring to gas cylinder, and noted Mike Melick had done these conversions.  I found his web site and it noted he no longer did the conversions.  I e-mailed Mike about doing the conversion, and his response was: "If you want to double cocking effort and get the same velocity out of it use the medium crosman ram".  His suggestion was to stay with the spring, add a top hat, tighten up the guide to remove the vibration, and add JM tar.
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Jim Stephens on December 27, 2018, 01:33:53 PM
scotchmo, hi this is thunder i have a 57 in .22 and an n-force that is 19x.080 can u tell me if u have a vido post that whold show the steps to installing the np the spring is broke in mine and since i already have the piston maby u could help with the in stall. thanks  thunder
Title: Re: Chinese air rifles and Gas spring conversions
Post by: Scotchmo on December 28, 2018, 04:20:58 PM
scotchmo, hi this is thunder i have a 57 in .22 and an n-force that is 19x.080 can u tell me if u have a vido post that whold show the steps to installing the np the spring is broke in mine and since i already have the piston maby u could help with the in stall. thanks  thunder

No video. Here is some info:

https://www.gatewaytoairguns.org/GTA/index.php?topic=20192.msg185663#msg185663 (https://www.gatewaytoairguns.org/GTA/index.php?topic=20192.msg185663#msg185663)

You'll need to remove the wire spring and guide from the QB57.

Easiest to install the gas spring with the body forward. You will need some spacing on the end of the gas spring. Maybe a short stack of washers if you have no lathe to make one. You can use a screw to hold the spacer/washers in place. The screw should not be too long as the gas valve is at the bottom of the hole and you don't want to release any pressure.