M1 Carbine conversion- Short 300 AAC/BO

[GrumpyOlGuy]

OCD caused me to try this: 110gr BC=.273. With ~1970fps at the muzzle, gives 9mm parabellum muzzle velocity and energy at 350+yds (about 100+ yards greater range than the standard carbine). Drops to subsonic at about 400 yds.

Uses 223 parent case, shortened 300 BO dies (to form case), and a 300 BO reamer with a standard barrel. Test results so far -- cycles ok with 12.0 to 13.0 gr WC820; ~2-2.5 MoA.

Why? Just to show what could've been done in 1940? Would've been the 1st assault rifle (Just sayin').

 

[#1buck]

Any idea what your chamber pressure is running? The bolt face would have to be opened up a bit to accommodate the rim of the parent .556 cartridge. The M1 carbine was pretty much engineered around the cartridge. There isn't a lot of extra meat to be monkeying around with in that action.
But I like where you're going with that cartridge idea. That is some good down range performance.

 

[#1buck]

I'm interested in this. Please post pics of the gun and your conversion process.

 

[a5werkes]

You may be interested in the 300 H'ammr cartridge.

Scroll down to view information videos by Bill Wilson.
https://www.wilsoncombat.com/300-ha...ail&utm_term=0_d7d9381842-911747e2ed-35900929

 

[Jim Watson]

That one won't fit a Carbine.
There were some interesting things done with $20 DCM Carbines.

 

[#1buck]

Thanks a5werkes but like Jim Watson said that won't fit in an M1 carbine. There are no more $20 DCM carbines to play with but I might play around with an aftermarket carbine.