Wednesday, July 24, 2013

Kitchen table cartridge conversions...not a good idea.

Every now and again, we get proof that someone, somewhere above has our back despite our best attempts at self-injury. My proof comes in the form of this stripper clip bearing these five rather unusual cartridge cases. Take a good look at them and see if you can guess what they are. (click on the image if you think that making them bigger will help.)Give up?

They're 7.62x51mm cases (.308 Winchester) that were fired through an M-1 Garand chambered for the .30-06 cartridge (7.62x63mm). They look funny because the shoulder has been blown completely out of the bottleneck cases. That the rifle continued to fire and eject these cases without any problems whatsoever is a testament to a great design, however it's NOT something that should ever be attempted deliberately, even in an emergency. In my case, it came about after I tried to change an M-1 over to the .308 chambering by use of an insert sleeve of the type that was once used by the U.S. Navy in an attempt to convert their stocks of M-1 rifles to that then-new NATO cartridge. This appealed to me because back then, .30-06 ammo was costing me $26.00 per hundred rounds but I could get .308 for $99.00 per thousand round case. (Those were the days, my friends...)
So to save sixteen cents per shot, I bought one of those insert sleeves for $15.00 and followed the instructions, which said to just put it on an unfired .308 cartridge, chamber it, and fire it. This was supposed to "fire form" the sleeve to the chamber, locking it in fast. Removal was supposed to be simple with a broken cartridge extractor. As is turned out, it was even simpler than that.

I'd fired several clips of ammo without a problem, but on one clip, I suddenly noticed over the report of the rifle (and the other firearms on the line) a change in the sound of my brass hitting the concrete. The sleeve had extracted with an empty case and the following cases, after firing and ejecting, had a distinctly different sound when they hit the ground. Fortunately my ear was attuend to little background noises like that and I stopped firing to check on the cause. I discovered five newly-deformed cases among the brass on the ground and realized that with the sleeve gone, I'd been shooting .308 rounds out of a .30-06. A lesser firearm might have reacted badly and caused me considerable harm, but that particular Garand just kept shooting. Wow.
Left to Right: .308 cartridge, blown-out .308 case, .30-06 cartridge.
Further investigation revealed that these chamber sleeves were supposed to have been loc-tited into place, a fact not passed along to me by the seller. Needless to say, I discarded it and never tried that conversion again.


  1. Important safety tip: double-check ammo size before loading.

    Got it! :)

  2. Yep, you were lucky... I've seen that before (once) and thankfully he stopped firing immediately!

  3. That's rather "interesting" in a "Glad you're OK" kind of way.

    Now that I have my M1, I'm having some trouble getting ammo that's loaded properly.

    I've been all over the forums, and to be *really* safe, you should only use ammo loaded to the military specs.

    Finally broke down and bought a couple of cases from the CMP.

    Makes me happy that when I bought my reloading gear I got the dies for 30-06, and a few thousand primers.

    Now I just have to get some powder....

  4. Yeah, those insert sleeves were a cute idea, but ultimately a failure.

    I loved the USN directions on seating them when they were first introduced. Fire two clips of 7.62x51mm through teh rifle quickly. Done.

    Of course, the Navy found out they tended to come out on their own, just as you found out.