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All Springer/NP/PCP Air Gun Discussion General > Show Off Your Air Guns With Mods (SHOW and TELL)
Big Bore Higgins
BigBird:
I modified my CO2 J.C. Higgins 22 (yes I know it is a classic - this was a $15 non-working parts gun) to shoot .308 (PB) using an old take off barrel in a unibody fashion where the breech is integrated into the barrel (barr-eech). The barrel is from a 30-06 Remington 700 and has about 17" of barrel and the rest is breech (turned down to ~ 3/4".
The reason I chose this gun to start was 1. It didnt work, 2. It has a longer breech, 3. There arent any holes forward of the valve (Crosman), and 4. It has a great trigger.
I am using pellets (currently undersized)
I was just trying to make a breech for the 22 barrel but it worked with the barrel so I didnt cut it off.
This is an ongoing project to learn about Lathe work and HPA (I know it looks like the spawn of snaggle-toothed Bubba). Ive tried to use "some" of what Ive learned here. I "hope" to make this into a 308 or 357 for medium game and would like to get power over shot count. For a hunting gun, 3 shots are ok if they can take down a coyote.
I fabricated the
Barrel/breech
Delrin spacer
Bolt - 303 SS
Bolt handle - 304 SS
Fill end - 1020 tool steel
Valve - 303 SS
Poppet - O1 & Delrin
Hammer - 303 SS
Transfer Port -303 SS
Valve
Valve
Valve
Couple minor faux pauxs on the valve. I forgot this seals in a larger diameter step down portion of the front of the tube, which can only be done really like the original screw on (or at least for me). I had an oring up front then used the location further back. It seems to work well. The rear half of the valve spring-anchor screws in 2 ways, one in middle to remove the poppet/spring and the outer to tighten down on the oring to seal the valve. I can remove the poppet without unscrewing the sealing portion (great for testing). I replaced the thin spring on the poppet from picture.
At this stage it holds air and shoots a declining string from 759, 646, 563 FPS on a meager but "safe" fill of 1400 PSI. I won't go higher due to the CO2 designed fill end.. I used 44.75 gr pellets for 57 FPE (78 joules).
Fill end
Fill end 2
End cap before
I would however like to add a tube extension for more air capacity. I will pin the valve with 2- 8-32 low head SHCS. I would use the thicker portion of the tube to anchor pins for the extension and test with my hydraulic pump. I could also use a bottle reg 1300-1500 PSI but feel that may be too restrictive for plenum (?).
The valve is designed to span all screw holes for strength and simplicity. Before there was a separate ring inside that "secured" the front trigger screw and breech screw.
The. 5/16 OD, 1/4 ID TP goes from the bore of the valve to well inside the barr-eech. I dont have any sealant it just presses up against the sides of each and top of barrel port.
Hammer is attached to the spring guide/handle and uses a 1/2 a spring from my Mauser firing pin spring. It is pretty heavy altogether but seems to have good lock time/force.
At some point I am planning to put a different breech (a QB 79 - thnx Mudbugmitch) and a 2 groove take off barrel from my "US Model of 1917 Enfield Eddystone Sporterized from Military Mongrel" (PB fodder - check youtube). It will give me 24" (17" now) and may look a little more normal.
Its not pretty but I think it works and is safer than original. I'm asking about more air tube and would like to get suggestions.
Thanks,
Dan
CraigH:
Great effort! Following the old Crosman integral breech and barrel design makes for a rigid platform. Pictures always complement a project. Well done!
Rob M:
awesome results ! i guess the next challenge would be to make a new main tube for it to handle even more pressure.. Id be curious to see the numbers on bulk co2 also.. nice job
BigBird:
--- Quote from: Rob M on July 25, 2019, 09:28:02 AM ---awesome results ! i guess the next challenge would be to make a new main tube for it to handle even more pressure.. Id be curious to see the numbers on bulk co2 also.. nice job
--- End quote ---
Thanks. A new tube would make more sense than adding an extension tube onto the existing tube. For an extension there would have to be a lot of metal taking up space for the connection and at least 4 pins (haven't done math on it). I'm not even sure it could be done. I have safety concerns too a it opens up room for error and creating a powerful/deadly rocket... For a new tube the only issue is my lathe is 7×14 with a 22mm spindle bore. I think I'd be using my steady rest and a file or farm it out. That discussion however might be better for the machining forum.
ezman604:
Thread moved to machine shop show & tell.
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