GTA
All Springer/NP/PCP Air Gun Discussion General => American/U.S. Air Gun Gates => Crosman-Benjamin Air Gun Gate => Topic started by: Tack Driver 10 on February 02, 2019, 09:51:45 PM
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Gold, silver, platinum, it's all good.
But for my next air gun project it's got to be stainless steel and brass.
Why stainless steel?
Because rust never sleeps.....LOL
Got some 3/4" OD T-316 SS tube to make some pump tubes.
The tubing as received isn't ready for prime time.
Honed the ID from .618" to .621" and gave the OD an initial polish.
This tube is cut to 20" and is destined for my next project.
A 2200 based 31xx chassis gun with a 1" longer pump tube.
The longer tube will allow a full brass valve instead of the short 2100/2200 valve.
Could possibly be the recipient of a balanced valve/multi shot configuration.
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Don’t make it too shiny. ;D The finger prints will annoy you.
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Mr. Don Cothran had planned to manufacture stainless steel 13xx tubes but encountered some problems with the "fissure" (the bottom opening where the lever goes up and down) as cracks would materialize.
Probably he uses a hydraulic stamping machine of some kind.
I pray success on your endeavor, Tack D sir ;D
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Thanks for the tips.
I'm more of a brushed metal kind of guy.
The tube has a slight tiger stripe pattern in it from the manufacturer that I like.
Stainless steel is work hardened so aggressive stamping or compressing can lead to cracking.
I'll be milling the slots so should be OK but I'll keep an eye on it, just in case.
We're all skating on the thin ice of modern life and cracks are inevitable.
Just got to keep moving in the right direction.....LOL
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Machined the slots and holes on the back end of the tube.
Just need to cut the pump slot and drill some holes for the pivot arm.
Here it is with the breech/barrel and trigger frame attached.
The tube will be trimmed about 2" to around 18".
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nice
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Milled the pump arm slot and drilled the holes for the barrel band.
The gun will use a NOS 766 pump link with the protruding rivets so needed to make clearance.
The stroke will be 4 3/4" with a 12 1/2" pump arm so will be easy to pump to high levels.
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Coming along nicely!
Are you finding that the stainless is any harder to machine than regular steel?
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Coming along nicely!
Are you finding that the stainless is any harder to machine than regular steel?
The 316 SS is quite a bit more difficult to machine.
Like a dog on a stainless steel steak house bone, I was all over it....LOL
Carbide drill bits and coated carbide end mills are a must.
Lots of oil and light passes milling the slots gets it done.
Definitely not a high production material.
Of the few SS tubes I've seen made, 304 SS seems to be the popular choice.
It's almost half the cost but also not as strong and corrosion resistant.
I'm guessing the Crosman tubes are some type of mild steel alloy.
As the saying goes, "Better ingredients, better pizza."
In this case, "Better materials, better air gun."....LOL
Here's a link to a build by Chevell using 304 SS and a 140 tube/pump link.
http://buddyl.com/edr/air/Crosman/chevell_build_pumper.htm (http://buddyl.com/edr/air/Crosman/chevell_build_pumper.htm)
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Thanks. I may need to upgrade my tooling before attempting a stainless tube build.
I had read that build by Chevelle years ago, but it was nice to read it again. I was always a fan of his work.
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Made the front pump arm pivot support from brass.
Used tapered SS 10-32 hex bolts and a black oxide shank bolt for the pivot bolt.
The mounting holes are slightly oversize so the bolts wedge in when tightened.
The brass nut is contoured to fit the curve of the tube so the bolt can't spin.
The bolt enters from the RH side so when the gun is pumped it will attempt to tighten.
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Subscribed!
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Looks overbuilt and tougher than a poso negro ;D
https://www.google.com/search?q=poso+negro&rlz=1C1CHBF_enUS761US761&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjjiI6ezbLgAhVG_4MKHX_mCNkQ_AUIDigB&biw=1600&bih=740#imgrc=h6cm0QJAclfQYM: (https://www.google.com/search?q=poso+negro&rlz=1C1CHBF_enUS761US761&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjjiI6ezbLgAhVG_4MKHX_mCNkQ_AUIDigB&biw=1600&bih=740#imgrc=h6cm0QJAclfQYM:)
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You have my attention.
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Made the valve, a three piece affair.
Sort of an air gun Menage a Trois....LOL
Just in time for Valentines day.
Cut the original top just ahead of the check so there's minimal dead air space and max volume.
This allows the ultimate in flexibility by altering the internal valve volume.
Regular valve, high volume/multi shot or even a balanced valve.
Like a box of chocolates except you know what you're getting....LOL
Machined the floor back .080" but left the throat at .200" as it matched the new .157" port nicely.
Cut the seat at 22 1/2 degrees along with the Delrin valve stem.
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beautiful work!
I'd absolutely love a custom stainless tube/lothar barrel hpa/bulk co2 2240, with a nice set of olive wood/pearl resin grips.
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Made the piston.
It's made to resemble the old Ash Can pellets.
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That is a work of ART!
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You may also like these versions from my "Gallery".....LOL
A modern version of the pellet piston.
My favorite, a NASCAR inspired racing piston.
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Ron, I am so impressed by your work! I think you're having almost all the fun!
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Ron, I am so impressed by your work! I think you're having almost all the fun!
Sometimes I feel guilty, being a "fun hog", but hey, somebody's got to do it.....LOL
In the meantime I did the final prep on the pump tube and assembled it.
Ran some quick tests and then cobbled this temp version together from various parts.
It has a Disco breech and an 18" Crosman 22 cal barrel.
I like the Disco breech since it has contiguous scope rails and the rear 4-48 breech screw.
The piston and valve have duro 70A poly O-rings for now.
Used a 2100 plastic pump arm but there's room for up to a 12 1/2" version vs the 11" stock arm.
Should be able to run some performance tests this weekend.
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Ran the gun over the chrony.
With 18" barrel and 14.3 CPHPs:
05 pumps 496 FPS 07.81 FPE
07 pumps 571 FPS 10.35 FPE
10 pumps 657 FPS 13.70 FPE
12 pumps 709 FPS 15.96 FPE
15 pumps 761 FPS 18.39 FPE
20 pumps 819 FPS 21.29 FPE
Initially used a 2400 hammer spring and the gun retained air with 12-15 pumps.
With 15 pumps got 693 FPS with a second shot at 481 FPS.
With 20 pumps there's probably two 700 FPS shots in the gun.
Switched to a 2100 hammer spring and it dumped 20 pumps.
Good starting point.
With a longer barrel and duro 90 O-rings, +30 FPS is a good WAG.
This gun is scary consistent with my 1322 SHO, be afraid, be very afraid....LOL
It got 821 FPS, 21.4 FPE with 27 pumps vs 819 FPS, 21.29 FPE with 20 pumps for this gun.
The 1322 SHO has a 3.5" stroke. 27 pumps x 3.5=94.5" of stroke.
This gun has a 4.75" stroke x 20 pumps=95" of stroke.
https://www.gatewaytoairguns.org/GTA/index.php?topic=153687.msg155696302#msg155696302 (https://www.gatewaytoairguns.org/GTA/index.php?topic=153687.msg155696302#msg155696302)
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This gun is scary consistent with my 1322 SHO, be afraid, be very afraid....LOL
It got 821 FPS, 21.4 FPE with 27 pumps vs 819 FPS, 21.29 FPE with 20 pumps for this gun.
The 1322 SHO has a 3.5" stroke. 27 pumps x 3.5=94.5" of stroke.
This gun has a 4.75" stroke x 20 pumps=95" of stroke.
Them ain't yer grandpappies pumpers...lol.
You do some awesome work Mr. Driver, carry on...
TMurray