GTA
Airguns by Make and Model => Crosman Airguns => Topic started by: Perry01 on March 24, 2014, 07:50:24 PM
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I recently installed a flat top piston and modified valve in my 1322 and have read that a 100 fps gain is what to expect. I also installed a 14.5" barrel and went from 400 fps at 10 pumps stock to 530 fps at 15 pumps using 14.3 gr. pellets. Does 530 fps sound about right for what I've done so far? There is a little compressed air leftover after 15 pumps.
My question is: what kind of gains are possible at this point. Will a stiffer hammer spring help and if so how much? I'm not looking for a 650 fps pistol but am curious as to the potential of the 1322.
I'm at 9 FPE right now. 560 fps or 10 FPE would be a nice goal.
Thanks...
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That seems about correct for what you have done.
If you have another original style valve, shaving about 4 thousandths off of the valve cone, and using the original cup piston and shimming, or using an aluminum adjustable piston that uses the original pump cup can get greater gains than using a flat top piston.
Also boring the transfer port a little and a slight angling can help.
Then add an even longer barrel (mine are 18 inch [on my 2289's (2289 is a 1322)]), if you want to keep it a pistol then a 14 inch barrel is likely your limit (some like even longer pistols).
For some secondary references:
http://www.network54.com/Forum/275684/thread/1226290086/my+2289%27s+official+introduction+%28lotsa+pics%29 (http://www.network54.com/Forum/275684/thread/1226290086/my+2289%27s+official+introduction+%28lotsa+pics%29)
http://www.network54.com/Forum/275684/thread/1169082692/I+just+did+another+%26quot%3Bstuffed%26quot%3B+plastic+piston%2C+this+time+in+a+bone-stock+2289--- (http://www.network54.com/Forum/275684/thread/1169082692/I+just+did+another+%26quot%3Bstuffed%26quot%3B+plastic+piston%2C+this+time+in+a+bone-stock+2289---)
http://www.network54.com/Forum/275684/thread/1353701149/Secrets+of+the+Stuffed+Piston+Revealed+%28Surprising%29 (http://www.network54.com/Forum/275684/thread/1353701149/Secrets+of+the+Stuffed+Piston+Revealed+%28Surprising%29)
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I have the DBO 2289 12" barrel. I installed a flat top piston and valve from A C Custom mods. Stock it shot Crosman Premiere HP 14.3 at 460 fps with the flat top it shoots 14.3gr at 525 fps all on 10 pumps. I haven't shot over the chrony with 15 pumps yet. With 10 pumps this pellet goes thru 2 tin cans at 10 yds, 15 pumps it goes thru 3 cans at 10 yds. I've got the steel breach waiting on my work bench to be installed, and a Leapers 3-9x40 to top it off
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I have the DBO 2289 12" barrel. I installed a flat top piston and valve from A C Custom mods. Stock it shot Crosman Premiere HP 14.3 at 460 fps with the flat top it shoots 14.3gr at 525 fps all on 10 pumps. I haven't shot over the chrony with 15 pumps yet. With 10 pumps this pellet goes thru 2 tin cans at 10 yds, 15 pumps it goes thru 3 cans at 10 yds. I've got the steel breach waiting on my work bench to be installed, and a Leapers 3-9x40 to top it off
Sounds good.
My 1322 came with a damaged transfer port seal and was leaking air right out of the box (I performed the tissue test). I'm going to make my own transfer port out of poly tubing tomorrow and check the velocity afterwards. I also ordered a stiffer hammer spring that should arrive by Friday.
Boy this platform is fun to tinker with.
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If you have another original style valve, shaving about 4 thousandths off of the valve cone, and using the original cup piston and shimming, or using an aluminum adjustable piston that uses the original pump cup can get greater gains than using a flat top piston.
can you please elaborate on this sir?
Do you know of someone who makes a pump air/piston design like this, that uses a factory cupped end with metal construction instead of the factory plastic?
And whats removing the 4 thousandths do?
Thanks
Ray
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Actually on some valves it's over 40 thou. (.040") It fits the valve to the cup better to reduce headspace. Properly done it also causes the cup to mate with the valve at the outer edge first, then roll the air to the center. Any adjustable piston for using the factory cup will be a one off, usually made by the end user.
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Hello. I am new to the some air gun mods but very curious. Why does the flat face valve give you more power the the cone type ?
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It's a matter of compression and headspace. The rubber cup of the stock setup has a lot of give. A flat-topped metal piston only has the O-ring that can compress, which can be reduced by proper design of the groove. Also removing the cone of the valve, removes that amount of the inlet hole's headspace, a large portion of the remainder can be eliminated by adding a pin to the check poppet. Reducing the valve's top to within .012" of the O-ring groove removes even more headspace. Ultimately it all adds to the pressure in the valve.
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So instead of waiting for a replacement transfer port seal from Crosman, I decided to fabricate a transfer port using poly tubing. The original seal was damaged and leaked but now there is no leaking air and the velocity increased as well. Thanks Nervoustrigger.
14.3 gr. CPHP pellets
10 pumps 519 FPS for 8.5 FPE
12 pumps 539 FPS for 9.3 FPE
15 pumps 580 FPS for 10.7 FPE
Not bad for the mods I've done so far. It dumps all air at 15 pumps but there is very little gain after 15 pumps. I'm pretty happy with this little shooter.
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It's a matter of compression and headspace. The rubber cup of the stock setup has a lot of give. A flat-topped metal piston only has the O-ring that can compress, which can be reduced by proper design of the groove. Also removing the cone of the valve, removes that amount of the inlet hole's headspace, a large portion of the remainder can be eliminated by adding a pin to the check poppet. Reducing the valve's top to within .012" of the O-ring groove removes even more headspace. Ultimately it all adds to the pressure in the valve.
Thank you
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Well I've had my 1322 for a couple of weeks now and the more threads I read here, the more ideas I get for new mods.
I got an envelope today from AC and in it was a new solid pivot pin as well as a new breech screw to replace that lame hex head one. More important though was the new stiffer hammer spring. I'm now able to dump all the air at 20 pumps. So far I've got a FT piston and modified valve, poly tube transfer port, bored barrel port, a 14.5" barrel and some trigger work. I shot it over the Chrony with 14.3 CPHP pellets.
10 pumps: 541 FPS
12 pumps: 568 PFS
15 pumps: 592 FPS
18 pumps: 615 FPS
20 pumps: 621 FPS for 12.2 FPE
My next project is to make an extended bolt probe. I don't know of I'm going to get any more velocity but it will probably help accuracy. I'm already shooting 1" groups at 20 yards but there is always room for improvement.
On the way is a 2289 shoulder stock, a 5" TKO, and a 4X32 compact scope and rings. I also ordered a 12" barrel from Crosman for when I want to use it as a pistol.
I've tuned my springers and gas ram rifles but this little pistol sure is fun to play with.
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Hey not bad at all...
I think that is about what my 1322 with a 14.5 barrel gets. I went a different route tho, until your bolt get to you you can use an allen
wrench or something similar to seat the pellet just past the port, that is what I do. I am guessing I will gain you about 10-20 fps...
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Hey not bad at all.. I am guessing it will gain you about 10-20 fps...
Another 10-20 fps would be nice. I have already gained 200 fps over the stock 1322. It's amazing how easy this platform is to modify.
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You're about maxed out for what you have.
I get 570 fps on 10 pumps with a 16" barrel using a 14.3 grain pellet and I've noticed gains of 7-10 fps per inch in barrel length.
Gil Irvin used to make an aluminum adjustable cup piston - I wish he was still around as he made me some amazing stuff.
If you contact Roy Weid at Mountain Air Custom Air Guns he will make you a Delrin stem for your 1322.
I am using 1/4" steel brake line for my transfer port sunk metal to metal in my valve, the barrel is countersunk 1/4" with a poly tube washer and a 9/64" transfer port in the barrel.
I am making 16 ft lbs @ 20 pumps, but I usually just shoot her at 10 pumps for 10 ft lbs.
If I need more I grab my Steroid 392 or a PCP.
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You're about maxed out for what you have.
I get 570 fps on 10 pumps with a 16" barrel using a 14.3 grain pellet and I've noticed gains of 7-10 fps per inch in barrel length.
If you contact Roy Weid at Mountain Air Custom Air Guns he will make you a Delrin stem for your 1322.
I am using 1/4" steel brake line for my transfer port sunk metal to metal in my valve, the barrel is countersunk 1/4" with a poly tube washer and a 9/64" transfer port in the barrel.
I am making 16 ft lbs @ 20 pumps, but I usually just shoot her at 10 pumps for 10 ft lbs.
If I need more I grab my Steroid 392 or a PCP.
What's the advantage of a Delrin stem?
I countersunk my barrel transfer port so the ploy tube fits nice and snug and was wondering how big to go on the port itself without having the pellet drop through. I'll try 9/64" as you suggest.
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The stem is flow enhanced behind the poppet. Are they using teflon from the factory now? My 1322 is an old model from the early 1990's that had the same seal as a 2240 just smaller.
If your poppet is white teflon just grind the stem down behind the poppet for 3/8" - take off about 30%. It will open up th flow path through the throat to the transfer port.
Also, pinning your valve with two 8-32 set screws will ensure your piston head space doesn't come out of adjustment from your valve moving slightly rearward.
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I just inspected the stem and the guy I bought my FT piston and modified valve from (Airgunsmith) already grinded the stem down behind the poppet. He also bored and angled the valve port.
I like the idea of putting set screws to secure the valve. That may be my next project.
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there's always a next project 8)
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I built a nice extended bolt probe out of the original brass bolt but now I need to tap the bolt to accept the bolt handle. Does anyone know what size the threads are on the Crosman bolt handle and what size drill bit to use?
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Hello. I am new to the some air gun mods but very curious. Why does the flat face valve give you more power the the cone type ?
As others have said it is a matter of reducing head space, and there by increasing the compression ratio. Less head space also means there is less air wasted in the lower pumps before much pressure is built.
Though flat top is not the only way to do this. If you make the standard piston stiffer by stuffing the pockets with steel rod, and then shave a little tiny bit off of the nose of the valve (so the cup fits the valve nose better), add a 4mil thick washer between the cup seal and piston, add a thin O-Ring around the outside between the cup seal and piston, you will get much better results than any commercialy available Flat Top Piston + Flat topped valve and it will only cost you a little less than $5. This reduces the head space more than the Flat Top Piston does.
For secondary reference see:
Secrets of the Stuffed Piston Revealed (Surprising) (http://www.network54.com/Forum/275684/thread/1353701149/Secrets+of+the+Stuffed+Piston+Revealed+%28Surprising%29)
New item on the dinner menu - Fresh Stuffed Piston! (http://www.network54.com/Forum/275684/thread/1320018763/New+item+on+the+dinner+menu+-+Fresh+Stuffed+Piston!)
And:
Washer O-Ring? (http://www.network54.com/Forum/275684/thread/1349994529/Washer+O-Ring-)
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The bolt needs to be threaded 8-32. I forget what # the pilot bit is - either #21 or #29. I will look in the morning.
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there's always a next project 8)
+1 And when there doesn't seem to be any, get another gun to modify!
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So I bought a 8-32 tap and #29 drill bit then threaded my new extended bolt probe. Only minimal gains were seen at 10 pumps but using 14.3 gr. CPHP pellets, it now shoots:
15 pumps 616 FPS
20 pumps 648 FPS
22 pumps 662 FPS or 13.8 FPE
With the extended bolt probe, it gained 27 FPS at 20 pumps. It dumps all air at 20 pumps but retains a little at 22 pumps. My goal when I set out was a 10 FPE pistol and if it reached 600 FPS I would have been pleased but I had no idea I was going to get it to shoot 662 FPS.
I'm done with the performance mods and am waiting for my 2289 shoulder stock, TKO and compact 4X32 scope to see how accurate it is at 20+ yards
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8) 8) 8)
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I am still waiting to hear the numbers at 10 pumps. I power mod to get the most power from the fewest pumps, preferring to keep under 8 pumps for high power shots :).
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I am still waiting to hear the numbers at 10 pumps. I power mod to get the most power from the fewest pumps, preferring to keep under 8 pumps for high power shots :).
550 FPS at 10 pumps
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Not bad at all. Nice work. You are getting close to my 2289g, I better watch out. Last I chronied it my 2289 was doing about 560 on 8 pumps and I have an 18 inch barrel on it.
So you are doing great.
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Not bad at all. Nice work. You are getting close to my 2289g, I better watch out. Last I chronied it my 2289 was doing about 560 on 8 pumps and I have an 18 inch barrel on it.
So you are doing great.
Thanks David. Maybe I spoke too soon as for performance mods. I totally forgot about the lighter valve spring. That's something I was meaning to do and I'm wondering if it's possible to cut a little bit off the one currently in there now. If so, any idea as for how many coils to remove from the spring?
Also, since I just bought a #29 drill bit and 8X32 tap, I'm going to pin the valve. That should keep the ports lined up under pressure. With the pinned valve and lighter valve spring maybe 700 FPS is possible.
I'm really just hoping for 600 FPS with 12 pumps.
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Not bad at all. Nice work. You are getting close to my 2289g, I better watch out. Last I chronied it my 2289 was doing about 560 on 8 pumps and I have an 18 inch barrel on it.
So you are doing great.
Thanks David. Maybe I spoke too soon as for performance mods. I totally forgot about the lighter valve spring. That's something I was meaning to do and I'm wondering if it's possible to cut a little bit off the one currently in there now. If so, any idea as for how many coils to remove from the spring?
You are likely better off severely over compressing the spring 20 to 30 times. Slide it on the shank of a screw driver and compress it until the coils are touching, hold for 30 seconds or so, release, repeat 20 or more times. This is what I did in mine and it works well.
Also, since I just bought a #29 drill bit and 8X32 tap, I'm going to pin the valve. That should keep the ports lined up under pressure. With the pinned valve and lighter valve spring maybe 700 FPS is possible.
Depends on how much you want to pump.
I'm really just hoping for 600 FPS with 12 pumps.
Have you already inserted a rod in the front of the check to partially fill the valve intake hole?
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You are likely better off severely over compressing the spring 20 to 30 times. Slide it on the shank of a screw driver and compress it until the coils are touching, hold for 30 seconds or so, release, repeat 20 or more times. This is what I did in mine and it works well.
Have you already inserted a rod in the front of the check to partially fill the valve intake hole?
Not yet, reducing headspace is always good but I'm not sure what kind of gains can be achieved by doing it.
As for the valve spring, maybe I'll compress it in a vise and let it sit for a few minutes?
Also, pinning your valve with two 8-32 set screws will ensure your piston head space doesn't come out of adjustment.
I decided to tap a hole on the top of the tube for a set screw so it's covered by the steel breech. Any idea as to what length set screw to use? 1/8"?
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You are likely better off severely over compressing the spring 20 to 30 times. Slide it on the shank of a screw driver and compress it until the coils are touching, hold for 30 seconds or so, release, repeat 20 or more times. This is what I did in mine and it works well.
Have you already inserted a rod in the front of the check to partially fill the valve intake hole?
Not yet, reducing headspace is always good but I'm not sure what kind of gains can be achieved by doing it.
As for the valve spring, maybe I'll compress it in a vise and let it sit for a few minutes?
I think that the repetition is needed (not 100%). So if you are willing to do that 20 times then I guess so.
Also, pinning your valve with two 8-32 set screws will ensure your piston head space doesn't come out of adjustment.
I decided to tap a hole on the top of the tube for a second set screw so it's covered by the steel breech. Any idea as to what length set screw to use? 1/8"?
I use 3/16th length grub screws.
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here's a link a saved on valve pinning .
http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,10015.0.html (http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,10015.0.html)
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You are likely better off severely over compressing the spring 20 to 30 times. Slide it on the shank of a screw driver and compress it until the coils are touching, hold for 30 seconds or so, release, repeat 20 or more times. This is what I did in mine and it works well.
How would I know if I compressed the valve spring too much?
Jeff,
I'm not able to view that thread on the Crosman air pistol forum. I tried to register but wasn't able to. Bummer...
David, are the 3/16" grub screws flush with your tube or are they recessed a little?
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Mine are flush.
Tape off .250" (1/4") on the tip of your pilot bit.
Carefully measure from the back of the tube to the center of the factory valve retainlng screw.
Repeat that measurement from the back of the tube where you want your valve pin screw located.
I highly recommend spotting your mark with a dremel ball tip deburring bit to avoid any drill bit walking.
Drill ONLY as deep as your 1/4" tape marking - not a hair more!
If your transfer port is angled you will want to make sure you aren't going to break through with your hole - I drilled mine between the breech and forearm.
Your tap will only start the threads - use some oil on it and when it stops, do not force it. Clear out any shavings. Start the grub screw and take your time - torque it down until flush. The grub will cut the threads as you go. A little turn, back it off, another little turn.....
Do one complete pin screw at a time if doing more than one. Drill, tap, install.
If you drill both and then tap, one will more than likely be off center and cause you grief.
If you want pics of mine PM me your e mail address and I will send them to you.
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Mine are flush.
Tape off .250" (1/4") on the tip of your pilot bit.
Carefully measure from the back of the tube to the center of the factory valve retainlng screw.
Repeat that measurement from the back of the tube where you want your valve pin screw located.
I highly recommend spotting your mark with a dremel ball tip deburring bit to avoid any drill bit walking.
Drill ONLY as deep as your 1/4" tape marking - not a hair more!
If your transfer port is angled you will want to make sure you aren't going to break through with your hole
Your tap will only start the threads - use some oil on it and when it stops, do not force it. Clear out any shavings. Start the grub screw and take your time - torque it down until flush. The grub will cut the threads as you go. A little turn, back it off, another little turn.....
If you want pics of mine PM me your e mail address and I will send them to you.
Mike, im following you for the most part but am wondering why just a 1/4". Don't I drill the pilot hole with the valve removed from the tube? Why is it important to just drill 1/4"?
I plan on using just one set screw directly above the valve retaining screw so I'll measure the distance like you said.
What do you mean by:
"if your transfer port is angled you will want to make sure you aren't going to break through with your hole"
Do you use 3/16" grub screws?
PM sent
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I drill the tube and valve together so they are both threaded.
If you drill deeper than 1/4" you will blow through into the throat of the valve and ruin it.
Wyoman on the Green did his under the breech - all I'm saying is take an internal measurement where your exhaust port on your valve is located.
You need about 3/16" meat in the valve for the set screw.
If your set screw is not screwed into the valve and just butts against it like the barrel grub screw in the breech you're wasting your time....that will not hold your valve in place.
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I drill the tube and valve together so they are both threaded.
If you drill deeper than 1/4" you will blow through into the throat of the valve and ruin it.
Wyoman on the Green did his under the breech - all I'm saying is take an internal measurement where your exhaust port on your valve is located.
You need about 3/16" meat in the valve for the set screw.
If your set screw is not screwed into the valve and just butts against it like the barrel grub screw in the breech you're wasting your time....that will not hold your valve in place.
Thanks for the explanation. Its crystal clear now. I'll make sure to take accurate measurements and drill just enough to tap both the tube and valve without going too far into the valve taking my time as I go.
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You are likely better off severely over compressing the spring 20 to 30 times. Slide it on the shank of a screw driver and compress it until the coils are touching, hold for 30 seconds or so, release, repeat 20 or more times. This is what I did in mine and it works well.
How would I know if I compressed the valve spring too much?
Simple put the spring on the shank of a screw driver, and with a washer compress it till the coils are touching.
Jeff,
I'm not able to view that thread on the Crosman air pistol forum. I tried to register but wasn't able to. Bummer...
David, are the 3/16" grub screws flush with your tube or are they recessed a little?
Close to flush.
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How do you retain pin in valve inlet when reducing headspace?
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Perry,
You're getting some good numbers, keep going!
For your valve spring, a 2240 or 13xx sear spring is a good one. I get similar numbers with similar mods. I used a sear spring in the valve, stock hammer spring with a brass guide in the hammer end of the spring. This adds a little weight and preload. I also used a Marauder exhaust poppet, they're harder material and easier to pop open. The Marauder poppet and sear spring are available from crosman, they're dirt cheap. Interesting build, I'll be following.
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How do you retain pin in valve inlet when reducing headspace?
I'm late to the party here, but I have done what your asking. I used a piece of music wire I checked and found in the junk box that "just" fit inside the valve intake hole. I sharped the end like a needle. I have the complete valve out of the gun and then heat the sharpened end of the pin with a torch and get it hot. Then use pliers to insert it into the valve intake and into the delrin check valve. Hold it a minute until I know its cool. Then I took the valve apart and put a little super glue on the pin where it enters the check valve. Not much, a half drop will do. Once this is done I put the valve back together and use a dremel tool to cut off the pin where its just flush with the valve.
Thx
Ray