Thursday, September 29, 2011

Kitchen-table cartridge conversions...never again.

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. That could have been very, very bad. Saved by the greatest battle rifle EVAH.

  2. Neat trick, good info to have, at least the tip of the 308 round protruded into the barrel so it functioned.

  3. Interesting. Straightens those suckers right out.

  4. Oh man, Good thing it didn't come apart on ya! I've never trusted those !@#&* inserts...

  5. Holy Crap! I've never seen that particular issue before. Glad you came out unscathed.

    And let this be a lesson to all those Garand bad mouthers out there.

  6. At first glance, I thought those were some .444 Marlin in that stripper clip, though the lower left corner of the photo reveals the cases to be of the rimless persuasion.

    Of course, I'd have been quite curious as to why .444 Marlin would have been in such an implement.

    I've got one of the original platforms for the cartridge, as well as one of Val Forgett's slick Italian copies of a Geiger/Rider carbine design.

  7. I've spoken with a few shooter's who've had the same thing happen to them too. I was always skeptical,thinking the cahmber insert would cause a jam.

  8. I also had one of those inserts but never had the nerve to install it in my M1. It just seemed too hinky. I would consider using such an insert in, say, a bolt gun or single-shot for versatility, but that's about it.

    Since the removal instructions state they can be more or less simply removed without an armorer's expertise by using a stuck shell extractor, it seemed to me that they would just eventually stick on a case neck and go flying away; and that seems to be exactly what happens.

    You know, as possibly dicey as this seems, it's a simple fact that when you work with firearms long enough, a certain number of hair-raising events inevitably occur despite the utmost care. I've had my share.

    Thanks for sharing.

  9. My guess had been that they were 30.06 cases that had been cut at the neck to make some sort of straight wall cartridge. I was about to try to work out what the case would headspace on and what caliber bullet it would shoot.

    Blown out .308 didn't even cross my mind.