Ammo design blunders

I can remember a couple of design blunders where careless dimensioning of a new cartridge allowed mixing it with some other similar-looking type of ammunition with spectacular and often tragic results.

I mean, in particular, the French 7.5x58 M1924C, which is very similar to 7.9x57 Mauser, and loading latter in the 7.5mm gun resulted in damage to the weapon, and the .300 BLK, which can be chambered and fired (once) in .223 gun with devastating results.

But do you remember any other blunders and mishaps of this type?

A typical and maybe the first would be 9x19 fired from 7.63x25 Mauser and later from 7.62x25 TT.

Though German troopers in WW2 did that regularly with lead core 9x19 from PPSh SMGs and when worn out too much they just took another gun.

People who did this with their C-96 (being dumb I guess and not knowing what ammo goes with it, or did not care as they had no 7.63mm on hand) often ruined their guns.

But wouldn’t the question on the subject already start with .223 and 5.56x45?

And what about calibers where the case was necked down to a smaller caliber and still would allow the round to be fired from the initially larger caliber gun (the bullet dangling down the barrel, not as dangerous but also not desirable). The examples there would be plenty.

Here a nice example of a .300 BLK fired in a 5.56x45.
Does this qualify as a squeeze bore?
Image from the web:


A 6,5x55 rifle rechambered to 6,5/284 is still tecnically a 6,5x55 but if you fire a true 6,5x55 the result would be bad.
A 8x57IS can be chambered in many 30-06 rifles (another squeeze bore).
Then there is the 300WM in 300Weatherby thing.

In Norway we call .308 Win/7,62 NATO fired in a .30-06 chamber “.30 Idiot”.
It’s a very frequent mistake as old myths and reckless/idiotic misconceptions about “.308 short” and “.308 long” being interchangable…

8x57 fired in .30-06 likewise is “8mm Idiot/7,92 Idiot”, and 6,5x55 (if you somehow manage to chamber it…) I’ve heard referred to as “.30-55 Idiot”.

I’ve heard of 6,5x55 being fired in 6,5-06 chambers, but just like with 6,5x55 in .30-06 chambers, you either need a rather roomy chamber and bolt face, or a lot of willpower and strength…


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Ole, remember, oxes are strong!

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On the SAAMI homepage (, under heading technical informations, a document listing unsafe gun/ammunition combinations can be downloaded. It runs to 14 pages …

I believe a relatively common one is firing a 20 bore in a 12 bore chamber

I remember a collector who had to proof his SIG 510 in .308. The gun came from South-America and was delivered to the proof house. He got a call : “Sorry, your rifle has blown up”. My first thought was they had loaded the gun with a 7,5 x 55 Swiss because the bolt had gone into pieces while the bullet hadn’t even left the casing. He never got an explanation (“Sorry again, we removed and cleaned up all pieces”) and was lucky a gunsmith could restore the rifle. It became a very costly collector’s item at last.

…And my second thought was they used pistol powder instead of rifle powder in the proofcartridge that ruined the gun.

A member of our shooting club was surprised that he could not hit the target at all with his .40 S&W pistol. He showed me some cases with obvious large expansion and asked me what I thought about it. The cases were 9 mm Luger and I was very astonished that his .40 pistol had functioned when firing 9 mm Luger rounds.

Just a little Bullseye to top it off right?

Kaboom! But it wasn’t laughable at all at that moment.

7,62 IDIOT as mentioned above…(O:

We had a club member who found some 44 Mag he’d reloaded ages before that had “gone dull” … we caught him just as he was loading the freshly tumbled (and now shiny) cases into his Taurus.

It took a lot to persuade him it wasn’t a good idea.


Many years ago, I fired some 7.62 NATO in a .30/06 M1 Garand…the cases came out straight, and as the rifle is a gas-op.semi-auto, the gun did not suffer from excessive pressure… but a few years later, at our Military Rifle club, a Newbie was firing his Columbian M1950 FN Gendarmerie carbine and wondering why the cases came out cylindrical…he was using 7,62 NATO in the carbine’s original .30 cal M2 chamber.
He was soon corrected; he said that was the ammo he was given with the rifle from its previous owner!

Btw, 7.62/.308 is a jam- headspace into the more tapered .30 cal chamber…so no headspace problem;
Furthermore, the bullet jump into the chamber neck before engaging the rifling and the shell case neck expansion lowers the chamber pressure curve appreciably…and of course the gas piston draws off more pressure.
Still, even in a strong FN Mauser action, not advisable.

Doc AV.

How about the very short lived, high pressure 9 MM Federal (rimmed) cartridge, which will chamber in an antique, and weak, break top revolver built for the black powder era .38 S&W round? Western Cartridge Company sold .38 S&W ammo with nickel plated cases and lead bullets coated with their shiny, copper Lubaloy finish. Side by side with the 9 MM Federal, which also used nickel cases and had a copper JHP bullet, the two cartridges look very, very similar. Oops! It’s a textbook example of Murphy’s Law.

The Taurus Judge and S&W Governor revolvers are good ones to be careful with since so many cartridges will fit into the extra long cylinder. You can fit .454 Casull, .460 S&W, or even .444 Marlin into them, but pulling the trigger will result in disaster. There are several others not to shoot in those guns.

Years ago, I was in my shooting range, next to me were Beavis and Butthead with a SMLE, the are feeding the piece with 7,65 Arg. ammunition, when I tried to explain them the differences betwen .303 rimmed and 7,65 rimmles, they told me “it’s the same bore diameter”, ok !!! Good luck, hope the coroner don’t have much work trying to remove the bolt from their forehead.

Back in the late 1950s a guy in Colorado Springs (as i remember) rechambered his Japanese rifle for 30-06 to use as a deer rifle. He hunted with it two seasons and killed his deer, but at the end of the second season he took it to a gunsmith because he thought the recoil was more than it should be. That is when he found he had rechambered a 6.5mm Japanese rifle.

The rifle was sent to the NRA museum and they ran tests on it, and there was no evidence of cracking or damage that could be detected. I have a hard time imagining the chamber pressure involved, but it says a lot for the rifle and the steel used in its construction.

A few years later I was out at the old range just north of Laramie Wyoming getting my rifle and new scope sighted in for deer season when I noticed five fired rifle cases lying on the ground. I looked at them and they all had a double shoulder. The headstamp indicated they were REM-UMC 7mm Mauser. I brought them home and later compared them to some other cases laying around and it turned out they were 7mm Mauser cartridges fired in a 7.65mm Mauser rifle so the end of the case fit into the bore of the rifle and firing left a second shoulder just below the mouth of the case. I suspect there were only five cases because none of the shots touched the target.


Somewhere in my collection, I have an article by P.O.Ackley about his experiments with 6.5mm Arisaka rifles. He rechambered the rifles for 7x57 Mauser, paying close attention to the chamber neck and throat. He reported that the rifles worked just fine, so long as they were properly chambered. It was his contention that blown up rifles happen because oversized bullets jam in the case neck when the chamber neck and throat are too tight.