GTA
All Springer/NP/PCP Air Gun Discussion General => Air Gun Gate => Topic started by: microsalmo on January 24, 2012, 01:27:20 PM
-
Gentleman, would you please look at the skirts on these piston seals and diagnose them... if that's possible? They came out of my Benjamin Trail NP. I can't keep this gun shooting straight, and I have had it apart three times, and checked all the obvious stuff many times over (barrel clean, lockup, stock screws, crown, shroud, scope, mounts, etc..)
I bought the gun new, and after 100 rounds through it, it was shooting 1" groups at 25 yards consistently with most any quality pellet. I took it apart and did a debur, chamber hone, brass barrel pivot washers, clean, grease, and added Charlie's trigger. After the tune, it again shot 1" groups for 100 rounds. Then with a lot of pellet experimentation, it started one-holing JSB Exacts at 25 yards. Over the next 250 hundred rounds, it would alternate between one holing and spraying, until it finally just sprayed all the time.... by spray, I mean 2" groups at 25 yards, and by one holing, I mean .30" or less at 25 yards for 5 shot groups. After this one started consistently spraying for 100 rounds, I gave up. The power seems good, but I do not have a chrony. The time to impact seems about the same as my other guns.
This one has me totally stumped, so I'm asking for help.. I've got two very successful tunes under my belt... one with a Remington NPSS that consistently shoots .30" groups at 25 yards, and the other with a Ruger Air Hawk that consistently shoots .50" groups at 25 yards.
I've noticed two obvious potential culprits with this Macarri seal. One, the cuts across the skirt, and two the burn mark on face of the seal where is smacks the transfer port. I've had my other guns apart a few times and their seals are perfectly smooth even after a few hundred rounds. All of the stamped slots & holes of this compression tube have been debured. What could there be up in the compression chamber that would cause these cuts? How can they be so uniform too all around the seal? And could they be the culprit of my accuracy issues?
Thanks, Steve
(http://i39.tinypic.com/25rc7sy.jpg)
(http://i39.tinypic.com/np2g4i.jpg)
(http://i40.tinypic.com/2yyrv49.jpg)
(http://i44.tinypic.com/2q1ctck.jpg)
-
First off the blue JM seal shows signs of dragging accross sharp edges when it was installed. If you deburred it then it is not good enough... :) Second thing is on inside of seal those should not hurt anything unless they have rased edges. If you show burn marks on face or edg of seal then that is caused by detination. To much Lube in front of seal. Make sure seal was not to tight in bore.
Detination can cause spraying of shots like you discribe. Use a chrony to determine what a 20 shot string give you.
-
Thank you Gene. So the cuts most likely came from installation? I guess I do need to debur agiain (will do). How could they be so uniform around the piston seal... there are no stamped pieces on the top of the receiver tube??
Detonation, hugh? Perhaps I am lubing wrong?? I've done all 3 guns like this, and the other two came out fabulous;
After a thorough clean...
1) pea-sized dot of Superlube Grease spread over an entire shotgun bore mop. Then, I run this mop through the entire compression tube on a cordless drill until there is the lightest appearance of a thin coat spread evenly throughout... so thin you cant feel but just see.
2) Honda Moly 60 Paste brushed over piston, covering 1" behind seal, sides of seal, and 1" at the end of the piston. This coat is also very thin and uniform... it's translucent.
That's it. It has worked great on the other 2 guns. Would this method of lube cause detonation?
Thanks, Steve
-
My Trail NP .22 seems to be doing something similar. I've asked for opinions in a different post. Pretty much checked everything but not tearing apart because of warranty. I can shoot two dime size 5 shot groups from 3o ft. and then miss the trap. :'( Still checking things out . Love the gun tho.... Good luck and hope you get it figured out.
KmiJ
-
theirs 2 other things that could be causing POI shift a bad fitting breech seal and your pellets, in consistant head sizes on your pellets will cause different POI! I know everybody thinks pellets out of the same tin should shoot in the same place but not so! pellets in the same tin can vary as much as 5 thousands of an inch and if the breech seal isn't fitted correctly will give the same POI shift, :P
-
Airgun Toys which you can find in the GTA mall has replacement barrel block brass washers. Might ask if replacement washers help accuracy. It is an upgrade which a lot of owners do.
-
Thanks for the feedback guys. I'll re-debur this thing first, and go from there. It would be nice to know form one of the professional tuners first; if my method of lubing is proper to minimize dieseling.
I'll check the breech seal too. I've already tried the kleenex thing, and it didn't budge... maybe it's blowing out the bottom??
Anyone have issue with the lube method? Would it cause dieseling? There is no smoke in the bore like during the first 20 shots after a rebuild, but I do get a VERY little at the breech when I crack it open still... and I have about 400 shots through this one now.
Thanks,
Steve
-
Airgun Toys which you can find in the GTA mall has replacement barrel block brass washers. Might ask if replacement washers help accuracy. It is an upgrade which a lot of owners do.
done, made my own - thanks
-
I don't know if you've checked it already but you could have a scope issue. Since it started shooting inconsistently at first and only later lost all accuracy it could have been a gradual then eventual total failure of the scope. You might try shooting with a known good scope to see if that returns accuracy. Lastly, don't give up. You'll find a cure if you keep at it. Good luck!
-
I am no pro, but I have tuned all my airguns to crazy accuracy.
I like my piston seals to fit nice meaning it doesn't take a lot of force to move in the compression tube.
Why would you use super lube in the compression tube, I would use Molly on a rag before that.
To be honest I don't use anything in the compression tube, just on the piston which will make it onto the compression tube.
With those seals being that tight you would scrape of all the lube, when cocking the gun, building it up on the backside of the piston seal.
When you shoot the sudden stop of the piston would force the lube (super lube + Molly) into the crosshatching, behind the seal in the uncocked position. When you cock the gun again, there will always be more lube then wanted until the gun burned it all off.
Done this stuff before, best to put just Molly on the edge of seal and 2 spots on the piston.. behind seal and bottom of piston.
It will work up onto the compression tube anyways. TOO MUCH LUBE.
The ding on the face of the JM seal is from the transfer port as the seal semi covers it.
Just my opinions.
Rob
-
Rob, thank you!!!
That all made good sense. I've got some Maccari Moly Paste too try too, and I think I will on this one. What are your thoughts on Honda's Moly 60?
The reason I used the Superlube is because I found an old document published by Charlie Da Tuna about lubes. It read;
"SuperLube can be a good lubricant. It has a silicone base with PTFE to help fill microscopic imperfections in compression chambers in synthetic seal guns and tubes but must be used sparingly as it will cause detonation."
And I have been using the Honda Moly 60 on all my guns because the same document read;
"Used as a lube for piston walls, spring guides, pivots, spring ends and many other applications. It is also used in home brews. There are not a lot of known sources for a good Moly lube in small quantities with a 60% ratio (preferably 65%) or higher. Don’t use the cheap low grade stuff from Wally World or part stores. Maccari of course has it and Honda does have one with 60%, although they may have to order it.
Honda part number…..Moly 60 Paste…….Part Number 08734-0001"
Is this document dated, and could it be part of the problem? Thanks again!
-
i had all the same issues with my g1 extreme after i converted to a np gun and i have so may parts here i was able to mix and match and try differant items and pellets, i did as some of you have done lube just the piston on both ends very lightly stress very lightly. one gun shot great and still does the other not so great. i have checked and changed everything except the compression tube and the gas ram. to no avail. i check the gas ram in the titan and the g1 extreme with the bathroom scale and one piston was consistant at 135 lbs give or take a couple lbs and the g1 extreme that was doing as your is would spray 2-3 inch groups, that ram was taking 105 to 130 lbs to compress in the scale. it varied almost every time i put pressure on the piston i got a differant ratting on the compression of the piston. is this the problem. i'm still not sure i have not needed anything from crosman so i have not ordered another ram yet but if you have a spare try it. as for the supper lube in the tube i don't put anything in the tube just a little moly on the piston.......dave
-
I suspect the uniform "scratches" on the side of your piston seal comes from, as Gene says, burrs....and the reason they are uniform may be that you pushed the piston straight into the chamber. Perhaps you could try gently turning it when you put it back in after deburring?
-
Even charlie recommends JM's moly...before the honda 60. It can be a substitute but JM'S is better.
The thinner the moly (viscosity) the easier it will migrate into the compression tube, when in a bind you can use moly 60 but less is always better. Same goes for JM's moly a little goes a long way.
Rob
-
Thanks guys. Do you put on JM's moly with a brush or with your finger?
I spent a long time deburing this tube... I guess not long enough. I just cant figure how it got cuts around the entire circumference when the cocking slot is only on the bottom of the tube? I will tear it apart and check again.
-
I sure would like to know your " honing " method. From the looks of the outer face of that seal, it is either too tight, a rough job attempting to cross-hatch the compression tube, or a mixture of both. Not talking down to you by any means, but one can really do more harm than good with a break hone and a drill. Those don't look like scratches from installation upon installation of the piston. Some folks are for lubing the pipe, and some folks are not. Me, it's a borderline kind of thing and rifle dependent with seal fit. If you feel you need to lube the tube before installing the piston, burnishing the comp tube with moly will aid the process. Just go easy and really work it in. Then buff it with a dry mop. You might not see any, but it is there;) "a little dab'll do ya"
-
I used the standard $20 brake hone from Harbor Freight Tool. The stone looks pretty darn fine but was without a grit label. I shot the tube with RemOil to get it good & wet, and made 6-7 passes with it at slow/medium speed? I tried to match the drill speed/pass speed to stay at the ideal 45 degree angle. I say ideal... that from my car building days of course. I did all the guns in this fashion - bad?
I'm thinking same as you... something is buggered up in the tube where I can see or feel. How else could there be cuts around the whole perimeter of the seal, right?
I'm open to any suggestion at this point. Thanks fellas.
... oh, and it is significantly tighter fitting than my other two guns. But so is the OEM seal from Crosman. I have both at the house, and they are the same diameter - the Maccari and the Crosman.
-
My guess the cuts are from the cross hatching.
My brake hone uses 280 grit stones. Used soapy water as cutting agent.
Too deep of cuts (less grit stone) the more damage will occur to the seal, don't want to polish it, just scratch it for the lube to cling to.
I suspect a low grit stone was used causing deep score lines in the tube, causing the damage to the seal when being cocked.
The worn area's on the seal lip are from the compression stroke and they are worn.
Maybe a finer stone is in order, to take the sharp edges off the compression tube.
Rob
-
Try this when cross-hatching. Draw a sink of warm water and add some dish soap to it. Place a wash cloth in the sink and allow the forks of the comp tune to rest on this on the bottom of the sink. Holding the hone chucked in the drili in one hand, and the comp tube at a 45 degree angle with the open side up. Make sure the soapy water is deep enough to allow a steady supply of fresh soapy water to enter the cocking slot while performing the work.
Another thing to keep in mind is not to have he tension on the home too tight within the comp tube. If you cant turn it with your thumb and first two fingers, then it is to tight. Be careful when pressing the hone to the bottoming out depth. Depending on the hone you have, you want nothing but the hone elements hitting the end of the comp tube. Spin the hone as low as you can go and work the honing from the end to the slot area. Cros-hatching as you would in the process at a medium speed. Too fast and you will remove too much material, and to slow may result in gauging the inner comp tube walls them selves.
Sizing the seal can be performed with a piece of all-thread, two nuts, two washers, a cordless drill and a fine file. A lathe would be ideal, but not everyone has a lathe or has access to a lathe. Hth's
-
Just a note about hones. Many of the hones have stones which are shorter than the metal carriers they are attached to. If the carriers are not shortened, you will scrape them on the back of the breach and the stones will not reach the bottom of the compression tube. The seal will eventually fail because each time it is fires it will run into the chamfer at the bottom. Additionally, it will also over time take the shape of the smaller diameter at the bottom and become too small to function properly in the rest of the tube.
pv
-
Thank you both.
I looked up the grit on the stone, and it is 220. Was that to harsh? If it was, I have had no such effects on seals in the other two guns. They are both smooth and void of any cuts. As for fit, the hone could be easily spun with my fingers in the tube. I did modify it with a dremel so that the tops of the stones made it to the end of the compression tube, rather than the metal plates the stones are glued to.
These are great suggestions. I will use the soapy water sink method going forward. As for the stone... at 220 grit is it ok, or do I need to search for something finer? Also, can I hone this tube again, or is it junk now? I cant imagine I removed to much metal if any?
-
IMO I'd say a combo of issues. TOO much LUBE, to harsh of grit on hone. The 220 grit will remove much material if you are not carefull. Debur is what it is and only remove what just has to be removed, no more. I am thinking that I used 400 grit on the ones I have honed. The consistant marks indicate a rough surface on contaminated surface. Brass barrel washers will help the barrel lock up. A hand held hammer impact will tighten up the barrel bolt much better than a plain screwdiver. Just hope you have not removed so much material that you have a lot of slop.
-
Thank you.
On the material removal... I hope not too. It sure fits tight enough. It's by far the tightest of my guns in that department. By the looks of the seal pictures, it seems real snug, no?
So are we sure on the 400 grit hone versus the 220? Do I need to go shopping?
-
OTHERS know more about these guns than me. I used hones forever on other things and to me the 220 is to harsh. 400 may be a little light for some. It also depends what and how you keep the stones lubed while honing. You can not get the tube perfect with the brake hones and you could get the tube out of round with high and lows if you don't keep the hone centered in the tube. You done need a rough surface for the seal to seat.
-
This is what I do,
Take gun apart, clean gun with brake cleaner ( well ventillated needed) Piston, spring, guides, inside compression tube.
Set everything a side on towel (old),
Start with compression tube (action), debur the cocking slot and sharp edges where trigger block is held and end of the action.
Clean with brake fluid again, use soapy water and hone to crosshatch( checked my hone 220 grit), rinse. Use dry cloth to rub out inside of the compression tube spinning the whole time. Use light and inspect, hit with brake cleaner again and let dry.
I would change seals now, and if still as tight resize and make sure the compression tube is spotless before reassbling.
Then move onto the rest cleaning everything over and over, debris will destroy.
Seeing you built cars, you know that anyways.
Rob
-
Wow, lots of good information... and a few contradicting answers.
How many revolutions with the hone guys?
Should I hone again with the 220?
Should I hone over it with the 400?
Soapy water or oil?
Do you apply moly with brush or finger?
Thanks, Steve
-
Myself, no need to hone again.
Inspect and clean may be needed. Looks like it could be debris causing those marks on the seal.
Does the piston have marks as well, as that would indicate grit in the tube.
If you have another seal I would use it.
Lightly use moly on the outside of seal lip and on piston, if compression tube is spotless, then re-assemble and shoot.
That is what I would do.
Rob
-
Thank you Rob.
-
... found a 400 grit hone at Napa this afternoon. $18
-
m, i'm looking at my spare unused piston (same part as yours). It is ~1inch diam. The cocking slot in this piston is ~4in long. This tells you the compression chamber is ~1in diam by ~4in long. A TRUE crosshatch would therefore be a one inch square X. The compression chamber is four(4) of those side-by-side X's in length.
Even IF you spun your drill slowly AND moved it in-and-out quickly, you still did not get crosshatching. What you got is a bunch of circular scratches perpendicular to the compression tube axis. Luckily, since 220 is not very coarse and since you did not run the hone stones dry, you did little or no damage. Unluckily, if you believe crosshatching is necessary (which i don't even tho i did it also), you're really not getting the (fabled?) benefit of crosshatching.
Let's review the history of crosshatching. It all started as a way to get lube into the compression chamber in order to ON PURPOSE cause combustion for more power. It took a while for people to figure out that was a bad idea for several reasons but mainly because the gun is not designed to take advantage of more power...it (piston mass, chamber volume, port diam, bore length, spring constant or ram strength, etc.) is not tuned for more power. Then the airgun community decided crosshatching was still a good idea, not for combustion, but instead to keep the piston seal lubricated. We really wouldn't want those piston seals (can you say 'synthetic', not 'leather') to dry out, would we? Do you really think any of our present day piston seals suffer from lack of lubrication?
Forget doing any more hatching of any kind at all. I submit that the piston seal skirt scratches are due to the seal being too tight a fit. Instead, put a new Crosman piston seal in OR a much looser fitting JM seal. The purpose of a JM seal is not to get more power. It is to get one that holds up better than the stock seal TO the stock amount of power and holds up with a reduced amount of lube...teflon, low coefficient of friction, slippery stuff, slipperER than the nylon(?) i believe the Crosman seal is made of. .
I submit that the damage to the piston seal face at the location of the tranfer port tells you that dieseling or just plain too much power for some reason or other happened and blew piece(s) of seal out your bore behind a pellet or two. It is possible that the stock gasram is too much more powerful than the spring these guns were originally designed for.
Look, once the pellet exits the far side of that treerat's head, you've proven you don't need more power. What are you trying to do, richochet the pellet off the tree trunk and hit him again with it? ::)
Plan on removing and examining the replacement seal after a few hundred rounds of having fun practicing & plinking. There should be no scratches on the piston seal skirt. There should be no missing seal material from the face of the seal.
Now, here's more bad and opinionated news. I submit that none of the above is what's causing your inaccuracy. I submit that seals as mildly damaged as yours don't cause inaccuracy and pristine seals don't guarantee accuracy. Look elsewhere for the source(s) of schizophrenic grouping. As I've posted elsewhere, the stock lock pin (like every other part on the gun) may have been loose (or too tight causing other problems). Is your action ever contacting the stock in inappropriate ways? Is your cocking linkage rattling around during firing? Is your trigger group touching the stock or trigger guard? Is your shroud loose? Are pellets hitting the shroud? Intermittent scope problems? When was the last time you minimized parallax? Why have you not popped for a chrony? Have you moisture-proofed your stock? If your cocking process is anything but silky smooth, there's a problem somewhere. I could go on but...thanks for posting your progress and for listening to my rant.
-
John has made some very good points here, but seein's how you've already done the hone IMO a little rough yes run the 400grt stones lightly to clean up the heavy scratches you've put into the tube and make sure it good and clean before you re assemble it with the proper amounts of lube in the right places JMHO :P
-
I would run a cotton ball in and out of the tube...everywhere a stone and file touched it. If you see snags then maybe it might shed some light? Then again you might not see any snags. Just a thought.
Patrick
-
As Gene mentioned the scratchs are from burs in the tube or it could be from the hone job. Ed
-
Hones have sharp edges when new, after they are used a bit, the edges become rounded as they conform to the shape of the tube. If your initial honing was just 6-7 passes, you only scuffed the surface of the tube with the sharp edges of the stones and got a less than optimum surface on the tube. If your home is set for too light pressure, you will not necessarily get a true honing as the stones may chatter. I would hone again, use the finer stones(you can also just purchase the replacement stones at auto zone) and I would run the drill at a bit higher rpm(2-300) and give it 8-10 strokes up and down. When done, the stones should have a rounded edge and you should be good to go. The idea is not necessarily to have a true 45* angle on the cross hatching, the opposing strokes are to create a more uniform surface. When you first run some coarse sandpaper in one direction, it leaves a highly scratched surface in one direction, as you change directions, it scratches more of the surface in a different direction. As you continue sanding and changing directions, the surface becomes more UNIFORMLY scratched. That uniformly scratched surface is what you are seeking. Should it take off a bit too much, you can always go to a slightly larger seal to easily solve that issue. Also, if you are going to get into this stuff(self-tune), you really need a chrony to check your efforts and it's the best way to know how your guns are performing over time.
pv
-
Some say to use the micro scuff pads. The honing is to make the tube uniform in ID. and what I call deglaze the walls so the seal can seat. One thing I am wondering is why is it when you brake down a new gun you see no cross hatching? Most I have looked at were shiny and smooth. I have not put a magnifier on any of them so there could be some and I never saw it. I agree with on the stones, they have to conform to the ID. of the tube. You will notice on hones that they will after use have a more curve look that flat. Many factors in using a hone on any thing. Amount of load on the stones,RPM, grit, timing of the strokes, lube, keeping the hone parallel to the tube not to mention the after cleaning and prepping. Not cleaning the object after the honing is as important as the proper honing.
-
Thank you all so much. I've read all your reponses multiple times.
What's everybody doing on moly application to the piston & seal skirt. I've got a jar of JM paste now. Is it best to apply a transparent coat with a hoby brush, or a little thicker uniform coat with your finger?
-
I replaced a seal on my hunter sport that was over-sized and saw the same marks on the seal like on your picture. Replaced with the correct size and no marks. Same accuracy issues with the over-sized seal that went away with the new seal.
-
Instead of investing in a bunch of seals that may or may not vary in size for a correct fit, why not size the seal. Everyone here seems to pop out the suggestion to simply replace the seal, when they (larger seals) can be sized down to be custom fitted better than an 'out of the bin' batch seal.
-
I have re sized, let me correct myself, tried to re size some seals. Some have worked and some did not work out. One thing I did not do is get a measurement of the ID. of the tube to compare the correct sizing. I had the mic for the ID. BUT FAILED TO USE THEM. Without the proper tools to size the seal I always wonder how true the OD of the seal is in circumference. I conducted mine with a bolt/nut and washer set up chucked to a drill. I used a mic and measured the old seal and made my adjustments from there. Finally gave up and bought replacement sized seals. Most of my trail and error was trying to make a seal from another make of gun fit another one due to not having a replacement on hand.
-
What's everybody doing on moly application to the piston & seal skirt. I've got a jar of JM paste now. Is it best to apply a transparent coat with a hoby brush, or a little thicker uniform coat with your finger?
-
I do the finger deal and a thin coat on both the seal outer lip and some on the piston as well. None in the piston chamber or front of piston. A dab of molly on the end of the NP shaft and a drop of silicone oil on the shaft as well. I also put some moly on the NP WHERE THE PISTON COMES DOWN ON IT WHEN COCKING. You more than likely can see scratchs on the NP where the piston has rubbed. Onthe trail you can get the bushing than glues to the NP to help keep the piston and NP IN MORE LINE. Less lube is better. No lube is worse
-
When I moly the seal, it is very light coat. Just like a haze of moly. Where you can still see the color of the seal, but with "flecks" visible.
Something that bothers me about your pics is that these scars look to be all the way around the diameter.....that would almost rule out burrs/sharp edges from assembly, unless it was put in and taken out many times, and the seal removed or turned each time.
I tend to agree with those who think the tube may now be a little rougher than it needs to be...or there is a tremendous amount of debris in there. Could be that the seal is too big, and creating some debris as it is shredded off.
Got access to a bore scope? that would confirm or deny. Possibly a cotton ball run up and down the tube.....if you see an "excess" of shredded cotton, maybe its too rough.
Good luck,
and God bless,
Farmer
-
Guys, thank you all so much for all of the great information. I read all of your responses very carefully.
Last night, I tore down the Trail for a good look at the aftermath of the last 150 shots or so.... or the round of experimentation where is started one holing pellets at 25 yards, only later to start spraying them again. The condition of the inside, and seal left me more confused, and didn't answer anything in my mind. What say you?
My observations, and please correct me if wrong...
1) the OEM seal looked great?
2) the Honda Moly 60 seemed to stay in place on the piston except for a 1/4 inch strip along the bottom where it was riding on the compression tube... is that normal?
3) the moly was still on the walls of the breech tube from the piston installation, and not spread around like I though it would be?
... the seal's skirt had some moly on it, but I wiped it off before I took most of the photographs. You can see how it looked when I pulled it on one photograph.
(http://i40.tinypic.com/i39pfp.jpg)
(http://i42.tinypic.com/5v50eh.jpg)
(http://i42.tinypic.com/2uegrvl.jpg)
(http://i41.tinypic.com/2r2ogg0.jpg)
(http://i42.tinypic.com/200g0a1.jpg)
(http://i40.tinypic.com/5pmvrd.jpg)
-
I'd say your good! I hope you clean out the tube real good before you reinstall the piston? but that looks normal, you might be a tic heavy on the moly behind the seal and on the piston behind just behind the seal JMO :P
-
I'd say your good! I hope you clean out the tube real good before you reinstall the piston? but that looks normal, you might be a tic heavy on the moly behind the seal and on the piston behind just behind the seal JMO :P
I agree. On the first pic of the seal, what is that around the outer lip of the seal? MOLY or piston seal edges. You got enough moly left to redo your lube on the piston.
-
You guys crack me up. I can go lighter on the moly for the rebuild. The ring around the seal is the moly before I wiped it off. If this is good, then why is this thing spraying & one holing intermittently??!!
The above pictures represent the shooting session where I was pulling my hair out. It would put 4/5 in a .30" hole at 25 yards then spray the next cluster into a 2" group. Back & forth it went until they were all shotgun. Maybe I should be looking elsewhere for an issue as suggested....
Is the moly supposed to stay put on the piston like that, or spread around the chamber? Charlie Da Tuna was telling me earlier that the Honda Moly paste is not thick enough to stay put, and would migrate past the seal causing detonation... I wonder if that is what's happening? I just don't know... the other two guns shoot straight with it.
:o
-
I blew up the compression tube.... anything telling there? There was no moly in it... making me think the piston was sealing, no? The silvery shiny area is the scouring from the hone, and runs form the cocking slot to the transfer port.
(http://i39.tinypic.com/2w4fpds.jpg)
-
:o Started reading your post without the picture showing:I blew up the compression tube.... and then scrolled down. That was a shocker. Have you put the brass washers in the gun and was the barrel locking tight up and down and side to side? ??? To much moly maybe. Reason none was in the chamber is that it burned out maybe. Could be a short between the rear and the front of the scope??? Just joking!!! I have had the same issue and never could pin point it for sure. Maybe just a BAD day.
-
Poo. I don't know. To tell you the truth, I'm so anal, I don't have bad days with my air guns. They all shoot stupid straight and stupid smooth, or they get worked on until they do. I only have 2 others, and I can't make them shoot bad unless I use the wrong pellet or something. Maybe there is another issue somewhere as suggested earlier.
The lock-up is great. I have made my own barrel washers, and they are specked to perfection. I use blue locktite and rubbing alcohol on all the stock & scope threads, so everything stays tight. I'm embarrassed to say it but perhaps I do have a scope issue, or need to scrub my barrel real good with JB Bore cleaner?
Yesterday, I checked the barrel, and it was straight with the shroud off. The crown looked real good too. The scope is a new Leapers 4-16x50 so I do not suspect it. But now that I think about it... how could it one hole, then spray, then one hole, then spray... then just spray like mad. Maybe the scope IS going/gone bad? I mean to one hole at 25 yards with one of these things is no joke. How could that all of the sudden go to poo?
Either way, I'm glad for all the help. It needed a better deburing anyhow, and as log as I was in there, I rehoned it in the hot soapy water as suggested. And of course, now can rebuild with less moly. By the way.. dang, when you guys say a little moly, you mean a little moly. I thought I had used just a little. :-\
-
I figure this is a nitro piston gun, so that eliminates twisting from a spring.
Check the cocking linkage, see how much clearance there is between the cocking shoe and piston.
If the piston hits the cocking linkage your accuracy will go to the poo's.
I do not know if you have the bushing kit from gene for the ram, but it might help.
Keep at it, the solution will show its self.
Good luck.
Rob
-
Microsalmo,
I still say check your scope. Take one of the scopes off of one of the two guns you KNOW shoots fine and put it on the gun that's giving you the problems. If accuracy comes back, you know for sure it was the scope. Then you can work on figuring out what if anything is wrong with the scope. Short of that, go through your current scope and tighten all screws, even the teeny-tiny ones on the adjustment bells and turrets and such. It wouldn't hurt and could help. If it were me though, I'd try another scope before going totally bald pulling out all of my hair in frustration trying to find any internal problems. ;D
-
I was thinking...have you tried shooting without the shroud or seeing if the barrel is bent to see what results you get. Not to send you on another tangent, but I ran into something similar where the shots were shifting point of impact as you turn the shroud when it is not properly glued on. I would remove the shroud and get tighter groups.
Somewhere on a post I read someone had a similar issue and unscrewed it out and re-glued it. Also another post someone found the pellet was hitting the shroud barrel cover that screws in. Just a thought.
-
Thanks guys. I will focus on the scope, shroud, barrel, and cocking linkage.
Thekid, can you tell.me more about what you meant? I don't quite follow what you were saying on the piston hitting the cocking linkage. You are speaking of the nitro piston, right?
What does Gene's kit do?
Anyone know if the moly is suposed to stay put on the piston skirts like that? I thought it would distrubute better after 150 shots, no?
Thanks.
-
Gene's kit centers the np in the gun.
When the rifle is not cocked, the end of the cocking slot on the piston will be very close to the cocking shoe on the cocking arm.
Sometimes the piston is too close and when shot, the piston strikes the cocking arm.
I had one that did this and the piston started to be stamped by the cocking arm at the end of the cocking slot.
Scope issue is possible as well.
Yes the moly stays in place for many shots, but will eventually wear off over time.
-
Ok. Thanks. It was ok there.
-
I rebuilt the Trail last night. It went well, but I have a question. This was the first time I didn't lube the compression tube for assembly, and it was dry & tight. Working the piston and seal back in was not easy. The walls of the tube were squaky clean, and the maccari seal really wanted to stick to them as I worked the whole assembly forward... I just went real slow and easy. I also used macarris moly on the piston and seal sides this time.
I visualised the moly on the piston and seal sides finally being distributed on the cocking stroke . I took five test shots afterwords. It was smooth cocking after 2-3 shots. The cocking stroke one the first few was a little squeeky as the seal ran down the dry walls the tube. It made that seal on dry metal squeegee sound. After a few shots, it stopped squeeking on the cocking stroke.
There was zero dieseling smoke. I loved that part.
Is this all normal?
-
Most synthetic seals are self lubricating.
The moly is really for a little fuel, for optimal performance.
Hope everything goes good from here on in, for you.
Good luck.
Rob
-
So it's normal to be a little dry & squeeky during installation, and for the first few cocking strokes?
Thanks, Steve
-
I fixed it ;D THANK YOU ALL WHO HELPED. The pictures represent 5 shot groups of each of the types of pellets I own; at 21'.
Row 1, 2, 3, left to right.....
Crosman Premier Hollow Points, Crosman Premier Hunting, Crosman Premier Lights, H&N Baracuda Match, Beeman Crow Magnum
RWS Supuedome, RWS Supermag, Beeman Field Target Special, Beeman Kodiac Hollow Point, Predator Polymag
JSB Exact Express, JSB Exact, JSB Exact Heavy, Crosman Premier Destroyer EX, Crosman Premier Wadcutter
(http://i39.tinypic.com/nzi0bk.jpg)
(http://i43.tinypic.com/nco5d0.jpg)
(http://i40.tinypic.com/11j27ip.jpg)
(http://i41.tinypic.com/2igj7fp.jpg)
(http://i40.tinypic.com/2vjd7dj.jpg)
(http://i39.tinypic.com/2jrshx.jpg)
(http://i41.tinypic.com/dbtmp2.jpg)
This is all great news. When my NPSS started doing this on my indoor range, it stacked its favorites into sub .30" holes at 30 yards. I can't believe I salvaged this gun. I was about to scrap it. :-\ I believe the RWS Superdome, the JSB Exact Heavy, and the Beeman Field Target Specials are going to be the magic pellets at distance. Even the Crosman Premier Hunting got 4/5 pellets into the same hole.
No real surprises on the magic pellets. My NPSS prefers the Beeman FTS & Crosman Premier Hunting as well.... coincidence?
-
Hi Microsalmo. Great to hear your gun is back to shooting well! ;D
What exactly fixed the gun? Was it just the removal of most of the lubes the last time you rebuilt it? Or did you re cross-hatch the cylinder to knock down some of the deeper scratches? Or both?
Either way, nice job sticking with it and curing that gun's ills! Feels good to finally get something just right.
-
So far it shows less is best; is this correct? (less lube and clean innards?)
-
yes! :P
-
Good to see you got her all straightened out.
You got the second stage of the addiction going strong...tuning.
Rob
-
WOW! Those JSB Heavy's and FTS are one hole groups! I shoot the FTS out of my TF 97 .22 and get the same results at 15yds freehand!
Congrats on having the gun running the way you want it!
-
Hey Guys,
Thanks so much for helping me out with this debacle. It seems so juvenile but I really wanted to make this gun a shooter, and it was frustrating the heck out of me.... guess I need to get a life, eh ???
I couldn't say just what fixed it because I started from scratch after I tore it down, and implemented most all of your suggestions. After the tear down, I took the compression tube outside and blasted it out with half a can of brake cleaner. Then I debured all the slots & holes again using 400 grit sandpaper & later a rubberized dremel cone. Then I wrapped 400 grit around a half inch dowel and went to work in the inside of the cocking slots some more. Then the fine emery went around a 1" dowel and i did the entire compression tube, following up with the 400 on the same 1" dowel. After a good rinse in hot water & simple green, and a flush with hot water, I got out the hone again.
I made 15 passes with the 220 hone while the compression tube was dunked in the hot water & simple green, focusing on trying to keep the cuts at 45 degrees to the tube. After a solid rinse in hot clean water, I blasted the compression tube out with brake cleaner again, and let it dry.
I lightly sanded the piston again with 400 grit, and washed it just as did the tube... first in the soapy water, followed by a rinse in hot water, then with the brake cleaner. It got a new Maccaari seal too, which I installed with a dab of Superlube to make it slip on without damage.
The barrel, I scrubbed with JB Non Embeding Bore Cleaner (again) & a brass brush. 20 passes followed by a good cleaning with Googone soaked patches, and then dry patches.
I applied Maccari Moly to the the right areas of the piston & seal sides and reassembled the gun. I also tried this moly on the brass breech pivot washers. When I reinstalled the shroud this time, I just barely snugged it down, and secured it with more thread locker. A drop of Remoil on a few hinges, and the proper washing of any threaded areas with alcohol, and I was about done. I applied thread locker in the right areas, and set everything aside to dry for 48 hours.
What can I say... it came out good. I put a few hundred more rounds through it today, and I just got smoother & smoother.
I'm eager to get it outside for some 25 yard + shooting.
Thank you all so much for coming to my rescue on this project. :D
-
I duno...you didn't hit any of the targets. You sure its fixed :P
Glad you got er working. This thread kinda makes me want to take another rifle apart just for the heck of it lol.
Patrick
-
Lol, was a bit shaky that day. On a serious note, I was using a 10 meter minimum AO scope at 21', so my cross hairs were dancing around a bit. I can't wait to get outside with this thing.
If this thread got you excited to tackle another project.... check out part two with the Chrony results. Woa, was I shocked!! http://www.gatewaytoairguns.org/GTA/index.php/topic,25575.new.html#new (http://www.gatewaytoairguns.org/GTA/index.php/topic,25575.new.html#new)
-
I would be very interested as to what you think finally fixed your problem also. Still having a few issues with my Trail NP as well. This has been a very informative post and I have soaked in a bunch of info...
-
jim, i can give you an educated guess, but i really dont know for sure. The evidence sugguets that there were a few things hurting me.
One, too much silicone lube, causing some light dieseling. I used superlube in super sparing quantities to aid in sliding the new piston/seal into place. It slipped right in, but i believe it pushed all the lube forward into the chamber as it scraped the walls clean. The light smoke and continued poor accuracy pointed to this issue.
Two, continued scouring of the piston seal. I believe i finally fixed this by deburing again... AND by sanding the tube with a dowel & 400 grit. It was suggested I hone with hot soapy water, so i did. This must have washed away any grit in the tube, as well as knocked down any high spots. I followed up with a hot water flush & half a can of brake clean. So im betting there was no residual junk in my tube to abrade the new seal. And it was a bugger to install, so I know it was squeeky clean.
Three, with the presence of dieseling, im sure my barrel was lined with lube. Goo gone, jb bore cleaner, and a brass brush ensured it was all out.
Four, I secured the shroud - just a little snug, and locked it down with blue locktite. It was said that overtightening here could throw off your groups as it torqued on the barrel. So i made sure it was not overtightened.
Thats all i really did different from the last few go arounds... and it got fixed. So your guess is as good as mine.
-
Theirs no guess work here you took the advice of those who know and put it to use and you see the results! :P
-
Theirs no guess work here you took the advice of those who know and put it to use and you see the results! :P
Exactly what i did. Research, and apply. There is no shortage of members willing to help here.
-
Being fairly new to air guns, I have been watching this subject progress. This was a little over my head, so I had no input to offer. The mechanical part of this is easy for me. The lubrication part confused me some. Wanted to say I just learned a ton from you guys Thanks.
-
A little lube is always better than No lube. Applying the correct lube to the right areas is even more important. Congrates!!
-
... it would be interesting to use a 400 grit hone as a comparrison. Or maybe the 220 followed by the 400? I found a 400 at NAPA for $18 ???
I wonder what effect it would have on things?
Thanks for following along and for participating guys.
-
never use anything but a 400grt in the compression tube JMO :P
-
That or scotch brite pads. Light on the metal. Chambers are soft metal.
-
Cool. I think I'll try the 400 on my airhawk rebuild & report back.
-
:D I had the Benjamin trail, it shot the same way I returned it. I will never look back either !
I am no expert but I am thinking the rifle barrel and its internal twist & its crown is what causes most of the accuracy, so if your seal shows scratches that more likely to cause different reduction in your fps, but I don't see why that would change accuracy at normal distances ,
the beeman R9 it does not have high fps but its very accurate.
also If using a brake hone is so precarious , why bother. a wooden dowel and different grades of and paper should do a good cross hatching .
I learned a lot from this post thread / I often wonder how a seal doesn't remove most of the lube because of its almost srynge like in the tube.
molly paste makes sense to me apparently when u cant see it its still there
Good luck with your rifle , please let us know how you made out.
Monday my new Hastan 95 .22 is coming Turkish walnut.
ordered a J m seal and I already know i will have to mod the piston button now that is one gorgeous rifle. very, very accurate/ I only hope the new seal is going to be just right!