View Full Version : M1 Carbine rechambered to 5.7 x 28 mm

4V50 Gary
December 19, 1999, 06:42 AM
Well, FN won't sell us the FN-P90 in a civilian form nor will they sell us their pistol in that same caliber. This got me thinking, why not convert the M1 Carbine to take this bullet? We could probably get some local manufacturer to conjure up the brass and then the challenge would be to adapt the magazine to take the smaller cartridge. (New follower, lips pressed in closer together, perhaps a mag body filler). Wouldn't that add a fun new dimension to the anemic carbine?

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December 19, 1999, 10:45 AM
Sounds like the old Johnson Spitfire round is what you might be looking for. That was a converted M1 carbine done in the early 1960s. Don't recall much offhand though.

4V50 Gary
December 19, 1999, 02:32 PM
Bolt face may need changes and with particular attention to the extractor. Also, the timing of the gun would have to be looked at and the gas port may have to be changed in size (no biggie if you're going to reline the barrel). I also wonder if the slide needs to have weight added or removed (affects timing).

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Unkel Gilbey
December 21, 1999, 03:16 AM
This may be out of line, or a new subject entirely, but the question about recambering the M1 carbine sparked this. What about recambering the M1 in .357 Mag? I've heard hearsay that this was something that some old Back woods types would do to add a bit more 'bang' to their carbines - allowing them to hunt deer more effectivly. Is there anyone out there with practical experience/knowledge of this?

Seems to me that if you were going to rechamber/bore the barrel into another cartridge, you'd do it in something that was readily available and more powerful (useful)?...

Anyway, that's my three cents worth.
Unkel Gilbey

4V50 Gary
December 21, 1999, 03:57 AM
I think it's been done Uncle Gilbey. Sorry I can't remember when, where or who.

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George Hill
December 21, 1999, 08:11 AM
Hmmm - instead of rechambering, Gary...
Why not develop a .30 Super-Carbine round?
With tougher brass and a mix of powders and a spitzer bullet - I bet you could get similar performance out of the M1.

Also - if the FN round is so Evil...
What About HK's similar round the .224 BOZ? I bet if FN is willing to alienate civilians - HK would be willing to help us out. If I remember right - the .224 BOZ was a little more hasty of a round anyway.

"A fear of weapons is a sign of retarded sexual and emotional maturity." - Sigmund Freud

December 21, 1999, 08:42 AM
The Spitfire round was the 30 Carbine necked down to .22(just had to look it up), so that conversion would work. The biggest drawback to the M1 Carbine is chamber pressure, it won't handle much more pressure than the original .30 round puts out, it was designed with not much extra strength to keep the weight down.

So actually, the best calibers for conversion will be comperable pistol calibers, perhaps take a Coonan magazine and tinker up the barrel and bolt to 357 Mag, or at the most do one up in 7.62x39, but that would be pushing the strength of the action, I think.

The simplest conversion would probably be to 9mm Win Mag, an unpopular pistol cartridge but one with the capability for more weight and downrange energy from a rifle barrel. I'd like to see one done up in .38 super, with the right powder, that could be a real screamer in a long barrel. I'd also like to see what the .357 Sig would do in a 16 inch barrel, that might be an eye opener.

The magazine is the problem with most conversions, but if there are mags already made, like for the desert eagle pistols, maybe those could be used. How about an M1 in .50AE? .44 mag? Lots of possibilities for someone with the resources to try it out.

Hope this helps.

With my shield or on it...

Futo Inu
December 21, 1999, 11:32 AM
IIRC, I read just the other day somewhere that one of the M1 carbine's current manufacturers is going to soon be offering new ones in 5.7mm Johnson! No conversion necessary. Dangit, where did I see that. I want to say a company called "A.M.I." or "I.A.I." or something similar - initials for a name.

[This message has been edited by Futo Inu (edited December 21, 1999).]

Oleg Volk
December 21, 1999, 01:59 PM
Who makes that round? I imagine no surplus is available...

30 Carbine is still possible to find in stores, though I am not sure how long that will last (hopefully long, as we tend to go through more range ammo than hunters do for real).

I am not so sure that trying to make rimmed .357 feed would be easy.

The other question: what are constraints on bullet weight. Would a slower 150gr bullet still wokrk with rifling, self-loading and existing sights?



Hard Ball
December 21, 1999, 02:24 PM
Around 1955 the US Arny experimented with a conversion of carbines to a new cartridge which consisted of the .30 Carbine case necked down to .22 taking a full metal jacketed bullet. All that was required to convert a .30 caliber carbine was to replace the barrel. It worked quite well. Many Army officers recommended that all the .30 caliber carbines in inventory be converted, but about that time the Army becams interested in the AR15 and the .22 Carbine development program died.
I believe that the Iohnson Spitfire cartridge was identical to the Army cartridge. If the .22 Carbine was available today it would be superior to the FN cartridge.