M1 carbine 5.7 Johnson ???

The bullet weight for the USGI M193 round has always been 55 gr. FMJ. The original loading for the .22 Spitfire was a 40 gr. bullet at 2800 fps from the 18 inch carbine barrel. It just did not have enough energy to compete with other rounds.

Bruce you're 100% right. Checked with my gunsmith and we are also using the 55gr. It was easiest to get in bulk. Sorry for the mistake.

rpw, the one thing you might want to check is the rate of twist in your barrel. If it is 1 in 14 or 1 in 16 then your best accuracy will be with a lighter bullet then the 55 gr. I suspect it very well may be the 1 in 14 which was very good for the original 40 gr. bullet. This is a guess on my part but you might want to check to be sure.

Barrels are NOS from iAi production. Twist is said to be 1 in 14. Function testing ongoing. Then velocity and accuracy will follow. It's a shame this variant never took off. It really seems to work extremely well. Bruce, thanks very much for the input. We've made about
2000 rounds of the 55gr for testing. If the gun handles them well then I'll go to the 50gr for the final bullet of choice.

rpw, Let us know how you make out with your testing.

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Originally Posted by lambo35

I have one of these. It has a Fulton Armory barrel on a CMP Plainfield receiver. It has had some feeding issues in semi-auto, I think due to different bullet shape/size and incorrect ramp angles. I've used a threaded brass plug to inactivate the semi-auto function, it is now a straight pull bolt action. I have not tried it out yet in its manual configuration. I understand that Melvin Johnson cured the feeding problems with a modified feeding ramp, I think it involved making two smaller ramps, side by side with a little change in the feed angle. I have seen an Iver Johnson receiver with that type of modification, but in .30 Carbine. I also picked up reloading dies, some empty cases and loaded ammo along with a finishing reamer. I would not mind loaning the reamer to a board member who is working on a project.

Chuck

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I'd have to question how you considered it a CMP Plainfield receiver. The CMP carbines are returned USGI models, not commercial copies.

Stickhauler, back in 2006 the CMP received a few hundred M1 carbine receivers from the Army, these included some Plainfield and Universal commercial receivers. I think the commercial ones sold for $50.00 + shipping. The rumor is that these were shipped as complete carbines to some S. American and Asian governments [army, militia, police] through our govt. I do not know who stripped them out, the lend lease nation or the US. They were not USGI issued carbines.

Chuck

Many of those Plainfield carbines were used on government installations by security forces that had the government contract for the location. Owned by the government and when no longer needed given to CMP as surplus.