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Air Gun Home Forum Index » Airgun Smithing » 2289 Crosman with mods=494.8 fps
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2289 Crosman with mods=494.8 fps 
PostPosted: Tue Dec 17, 2013 9:20 am Reply with quote
tommylucky
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Joined: 11 Dec 2012
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Location: Portsmouth Va
I got my Backpacker Bugout kit last Christmas. Since then I've added a steel breech, Mellon Extended bolt,Mellon Flat Top piston and Mellon valve.
It performed OK, accurate for about 100 ft of so. It was only popping out lead at about 420 fps.(not enough) I still had my original valve and decided to experiment.First I flattened the dome and left 1/16" more than the Mellon had to bring compression up a bit. I drilled the valve out roughly 1/32 inch larger and worked the exhaust port to remove the right angle the air had to go around. Then I took all the innards from the Mellon valve and put it in my modified stock valve.I also replaced the port valve with some ice maker tubing, and replaced the hammer spring with one from a Remington 77 pumper.
Yesterday, at a friends house I got to test it out on a chrony. Since the valve is opened up it takes more pumps to fill it to max, but the results were surprising. At 30-yes, 30 pumps it now makes 494.8 FPS.
I think I'll try lightening the hammer some next mod. The lighter it is, the faster it can move.I know that taking too much off will lead to diminished performance so I'll be taking off a little at a time. The big mod will be the pump. 30 pumps is too much work.

Wile testing the speed I tried with and without my suppressor. It seems to travel faster with the suppressor than without. Funny. By the way, my suppressor is home made. Its a 1" tube of thin walled aluminum. I fitted a washer to the front and peened the sides to hold it firmly.Inside is a baffle made from a pilot bearing tool(plastic) Its cut down and drilled through to fit the tube. This is all held to the barrel with 2 cut down sparkplug boots slipped onto the end of the barrel. The front sight is removed .
It works wonderfully. Not as quiet as my buddys FX Indy, but it didn't cost 2 grand either. I'll post some pictures so you can try this yourself.
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PostPosted: Tue Dec 17, 2013 11:32 am Reply with quote
rsterne
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With an F-T-P and valve, the gun should have been way over 500 fps wi no other mods.... Did you adjust the length of the piston so that it was touching the valve?.... If an F-T-P doesn't touch the flat end of the valve, it won't build pressure properly....

Bob

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mllon ftp 
PostPosted: Tue Dec 17, 2013 12:37 pm Reply with quote
tommylucky
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Joined: 11 Dec 2012
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Location: Portsmouth Va
the valve is non adjustable. That's one of the failings I found in it. Its well built but without the adjustment I can only do so much. This gun only shot 13.4 grains .22 pellets at 430 fps when new.
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PostPosted: Tue Dec 17, 2013 8:29 pm Reply with quote
AirGunEric
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Bob's not talking about the valve- the piston needs to be adjusted correctly.

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PostPosted: Wed Dec 18, 2013 11:23 am Reply with quote
ace
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I agree theres something not right with your setup, as Bob mentioned your FTP should just be touching the valve top when pump handle is closed , my backpacker is doing 500fps at 10 pumps.
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typo 
PostPosted: Wed Dec 18, 2013 12:25 pm Reply with quote
tommylucky
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Location: Portsmouth Va
I should have said the piston is non adjustable. Im going to disassemble today and see whats what.I have a piston with adjustment that I made from and old Crosman 1400. Its the cup type.
I realize that its all about storage, release and delivery of the compressed air.
The chrony I used shows a Benjamin Marauder pistol at only 560 fps. Maybe the chrony is flooey.
Either way, I'm pleased with the backpackers performance now. It seems to shoot a lot faster than it did stock. More to come.
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PostPosted: Wed Dec 18, 2013 3:32 pm Reply with quote
rsterne
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I've never seen a Flat-Topped Piston that ISN'T adjustable, you have a Mellon FTP, right?.... It says "adjustable" right on his website....

Bob

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OK I found the adjustment 
PostPosted: Mon Jan 13, 2014 2:41 pm Reply with quote
tommylucky
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Joined: 11 Dec 2012
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Location: Portsmouth Va
I located the adjuster and tuned it a little. Now, with 10 pumps it shoots 480fps. at 15 pumps its at 525fps. 30 pumps results are 585fps. So with a little more work it'll pass 600fps. not bad for a 2289.
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PostPosted: Sat Mar 08, 2014 7:54 am Reply with quote
DavidSaunders
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I have found it is easier to reduce the head space to near zero with a cup piston than with a Flat Top. My 2289 that has a Cup piston is shooting right at 11.6FPE=604FPS on 10 pumps with Crosman Premier Dome 14.3 grain pellets.

All I did is stiffen the stock piston with steel rod, shim the cup with delrin ring, add a delrin shim in front of the Valve o-ring to take that head space, shaved the nose of the valve to better match the profile of the pump cup, add a piece of rod to the front of the check valve to take the head space in the inlet port, added a spring guide in the valve to reduce the volume, ported the valve, did the poly tube transfer port, and that is it for power mods.
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2289 Crosman with mods=494.8 fps 
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