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All Springer/NP/PCP Air Gun Discussion General > Big Bore AirGun Gate

First big bore build

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Scotchmo:
I'm using my 100+fpe .22 HP build as the basis for a .257 long range gun. I'm looking to get in the 180fpe range.

The base rifle is/was an Armada .22 but there are few original parts remaining (receiver, handrail, modified air tube and gauge block, plug/endcap). It still looks like an Armada.

Electronic hammer/trigger
Cothran Powerhouse valve
Custom single shot breech with 0.250" ports
36" bull barrel (0.875" dia) with TJ 25-20 liner
215cc plenum
2000cc, 300bar bottle
Ninja Flex regulator (3000psi max)

It's for bench rest. Weight will be ~19lbs without scope or bipod.

Currently using a 450cc tank. Waiting on the 2000cc tank. I have the barrel blanks. I just need to make some time to get to the shop. I ordered an Arsenal 257420 Boat Tail mold (70gr), but they are backed up with orders so that won't be in for several weeks.

Hobbyman2007:
Sounds like fun . Love the flat shooting 257 . Too bad it’s way overkill for hunting. I think you’ll  really like the 257420 mold. Keep us posted

mackeral5:
This one should be very interesting.  Big plenum, LOOONNNNGGG barrel. 

I have a 35" TJ's 25-20 in process for one of my Bulldogs, it will be used both regulated and unregulated, should be interesting to compare notes.  The gun previously did a little over 165pe with 72gr at 3000psi, but with a 27" barrel.  Hoping for similar energy levels as you but not having to run it near as hard as was required with the 27" barrel. 

rsterne:
Sounds like a great project.... 180 FPE on 3000 psi will be a good power level, if it can be done with decent efficiency.... The 36" barrel will, of course, help in that regard.... I would be looking at a heavier slug, however, that works out to 1075 fps with a 70 gr....  :o

Bob

JuryRigger:
Watching,
Jesse

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