5.7 mmj

[eb in oregon]

Howdy,

This is my first post on this forum, so bear with me. I'm just finishing up a tour in Iraq, I'll be home at the end of May. While deployed I purchased an IAI Carbine in 5.7 MMJ that's waiting for me in my shop.

I'd like to play with this caliber, I've wanted one of these rifles for years. And I've cast and loaded thousands of bullets for pistols, but never a rifle caliber (well, I did play around with .308 some years ago), especially of the small caliber that this rifle is.

My question revolves around bullet weight and design. Can anybody give me "a leg up" on a good selection of bullet that works well in .22 caliber cast bullets? I may also try some of these "boolits" in a .223, so interchangability could be a consideration. Any comments are appreciated.

eb

[eb in oregon]

Nobody's into .22 caliber's?

[mtnman31]

Check the twist rate of the barrel when you get home. Many 5.7 MMJ's were barreled with twist rates that were best suited to lighter .22 cal bullets, i.e. 40-50gr. I don't recall what was standard for the IAI's.

I don't own an MMJ yet, but have been doing my research. I did pick up a Like-new set of 5.7 MMJ RCBS dies for 10 bucks a while back.

[bruce drake]

I use the LEE Bator 55gr Mold from Midsouth Shooting Supply in my 22-250 which has a 1-14" twist. I don't know your twist rate but the BATOR is a good RNFP mold that is gaschecked as well so you can push the velocity over 1600fps easily.

Bruce

[eb in oregon]

I've considered only bullets between 40 to 55 grains in weight, but thinking that something around 45 grains might be optimum for this cartridge. As "mtnman31" mentioned, the barrel twist will be the determining factor in bullet selection.

I've not read anything before that states the factory twist rate of the IAI carbine, though I've not spent more than a few minutes "goggling" the subject. It will need to be the first thing to do really, determine twist rate.

I was fortunate that the rifle I picked up included a set of dies and about 75 loaded factory ammo and the same in fired cases. And, as I've had .30 Carbine ammunition on hand for years, additional cases aren't a problem.

I figure that I'll be looking at velocities of around 1600 fps or less, which will still be respectable in muzzle energy within 300 yards. Practically speaking this is a "short range" cartridge to begine with.

And again, as I've got a .223 semi-auto, the ability to use the same bullet for both cartridges is something I'd like to consider.

[oldhickory]

I've thought about one of these rifles, but never got around to buying one. I think you're on track with a 40-55gr. boolit. I think I would go for a 45-50gr myself.

I can see some advantages over the .30 Carbine, but I could just never bring myself to alter a good G.I. carbine to play with it.

[BarryinIN]

I've never worked with one, but this may help:
http://johnsonautomatics.com/messageboard/
It's a Johnson Automatics forum. Most of the activity is centered around the M1941 rifle, but there is a 5.7mm Spitfire section.
At least one of Melvin Johnson's sons posts on there, and he has been a huge source of info for the M1941s thanks to him managing to hang onto some of the old records and papers. Perhaps he will have some original load data, or someone else might have some newer data.

[eb in oregon]

Thanks Barry! The 5.7MMJ forum is looking a little bare, but I'll see if I can get "some bites." I'm just guessing here as I've not looked at any loading tables for thr 5.7 for some time, but the powders usable in .30 carbine are probably good for the 5.7 also. I try to avoid adding another powder if possible. I've got too many as it is.

Eric

[BarryinIN]

I don't follow the 5.7 section of that forum closely, so didn't know it was so slow until I checked it after posting that. It is pretty lonesome around there.
But there are some people there who know a lot about the history of Johnson and the company, and I bet if you ask, someone might know what it was originally loaded with or what they tried.

A book on Johnson and his designs came out a couple of years ago. I looked through it to see if there was any loading info you could use, but didn't find anything. It's fairly detailed, so I thought there might be something and was kind of surprised there wasn't.
The authors of that book (Cabfield, Lamoreaux, and Johnson) are on those forums a lot, and might be able to tell you something.

[Blammer]

MMJ? what does that stand for?

[madsenshooter]

Melvin M. Johnson

[eb in oregon]

There is a nice section on the 5.7 MMJ in Frank Barnes "Cartridges of the World," (I can't remember what edition I have) and in Donnelly's "Manual of Cartridge Conversions" which has several good loading tables. I'm truly looking forward to playing with this cartridge and rifle when I get home.

"old hickory," keep an eye on Gunbroker, I picked mine up there and I've seen one or two others in the last few months. Another IAI Carbine was priced just a tad high, the other was an already converted M1 Carbine that went for more than I paid for this one which included dies and ammo.

These are getting few and far inbetween now, I'd snap another one up given the opportunity.

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=161306652

Eric

[jhalcott]

I'm using 40 and 45 grain JACKETED in my gun with 2400 powder. Be carefull as it is easy to bend the op rod with to harsh recoil.

[eb in oregon]

I'm wondering how that could be? I've shot thousands of rounds out of .30 Carbines, and I fail to see how the recoil of a 45 grain bullet could be "harsher" than a 110 grain bullet.

There will be a velocity difference, but physics dictate the recoil should be milder, not harder. If this happened to you, could it not have been a bad operating rod to begin with? And are we talking about the "operating rod" which is a part of the Slide, or the return spring guide rod?

I don't see how the piece of the slide that interfaces with the bolt could bend, but I imagine it is possible with a bad part. As for the recoil spring guide rod, these are known to be "cheezy" in the first place and frequently do bend. In the past I've made new ones out of stainless steel and that problem goes away.

eb

[scb]

Mine didn't bend, it broke. about 30 years ago. Was loading too hot. Primers were starting to flatten. Seems like I was loading imr4227.