Help identify a curious 6.5MM cartridge

[Hcompton79]

I'm wondering if anyone can help me identify the cartridge I have had sitting above my reloading bench for some time. It is definitely a 6.5mm cartridge. The bullet measures 0.261" (6.66MM) in diameter at the case mouth, the case length is 1.981" (50.30MM) and both the rim and base measure 0.446" (11.32MM) in diameter.

The curious thing is that this case is headstamped with what appears to be "DM 42" which I would assume means Des Moines Ordnance Plant in Iowa, 1942 production. However the dimensions of the case almost match a 6.5x50mmSR Arisaka cartridge.

Is this a 6.5 Arisaka cartridge? And if so what were the Americans making this in 1942 for?

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Information

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[Daan Kemp]

You would be surprised at how many Arisaka were in use all over the world. I believe Home Guard in Britain had some, Russia had some. All good reasons to supply ammunition.

[jonnyc]

No, sorry, nothing odd or historical. Some reloader just went to a lot of trouble to make some ammo to shoot in his bring-back Arisaka, and the only brass he had on-hand was some US milsurp .30-06.

[rcathey]

No, sorry, nothing odd or historical. Some reloader just went to a lot of trouble to make some ammo to shoot in his bring-back Arisaka, and the only brass he had on-hand was some US milsurp .30-06.

I have some 8mm Kurz made the same way.
Fun little slice of The American Spirit. “We’re gonna fight you, we’re gonna beat you, then we’re gonna take your weapons home and play with them.”

[browningautorifle]

Some reloader just went to a lot of trouble

Exactly that. Just pulled a bullet and sized a case down to make it useful with original primer. I did the same with some IVI 7.62 when I made some .300 Savage. Now there's some about perfect IVI 300 Savage FMJ out there for collectors...

[Sunray]

DM also means: Deutsche Waffen-u. Munitionsfabriken A.-G., , Früher Lorenz , Karlsruhe, Germany and Deutsche Waffen-u. Munitionsfabriken A.-G., (Previously Deutsche Metall-Patronen-Fabrik), Karlsruhe, Germany.
.261" doesn't match any 6.5 Jap ammunition. Bullet diameter is .264". Rim diameter should be .466". Case length 1.984". Isn't made out of a .30-06 either. Its rim is .473". So's the .308.
Still very likely to be a home made case though. At one time, other than Norma ammo, there was no 6.5 Jap ammo available at all.

[browningautorifle]

Isn't made out of a .30-06 either. Its rim is .473". So's the .308.

Oh good...you're talking from some book you're looking at. I just went and measured 8 separate .308 cartridges from several countries and they measure .462, .463, .467, .468, .469, .470, .4705, .472... Some were North American and some weren't but all were in common use during the last 35 or so years... Several were identical headstamp but different rim diameters.

Anyway, it doesn't matter. The OP's cartridge will need to be searched out a bit...

[CINDERS]

Were talking 20 thou difference from what may be printed in a book to whats in the OP I seriously doubt in the case of ammunition that they the Jap's or any power for that matter is going to worry about a 20 thou difference in rim dia when there is probably more play in the action dimensions of the rifle.
We were all at war so getting it close enough within reason so it could do the job would suffice......................

[Hcompton79]

I had my suspicions that it was some handloader's post-war attempt to make 6.5 Jap, however I didn't think anyone would go through the effort to turn down the base diameter of a .30-06 case. However, I have seen people do things like this when no ammunition exists for a particular arm. Idle hands perhaps.

[browningautorifle]

I didn't think anyone would go through the effort to turn down the base diameter of a case.

Absolutely, yes. You make them individually and then they're gold to you.