.303 into 7.7?

[Jim K]

The 7.7 Rimmed IS the .303 British; it was used by the Japanese Navy in license built copies of the Lewis gun and Vickers belt fed machine gun. The former was used in flexible mounts on aircraft as well as being used as a ground gun, the latter was used as a fixed gun on aircraft (Type 89).

The 7.7 Semi Rimmed was used in the Hotchkiss copies fed with stripper clips. Neither the rimmed nor the semi-rimmed will fit in the Type 99 rifle because of the large rims. It is reported that the 7.7 rifle cartridge will work in the Hotchkiss machinegun, but gives malfunctions because the extractor doesn't always catch the rim. Not having one of those machineguns, I can't confirm this.

FWIW, the 7.7 Japanese rimless rifle cartridge will feed and fire in the M1903 Springfield; even the clips will work. The result is a short necked case, but no signs of excess pressure. It will not work in the M1 rifle, because it is pushed too far into the chamber for the firing pin to reach the primer. NOTE: THIS INFORMATION IS FOR DISCUSSION PURPOSES ONLY; I DO NOT RECOMMEND OR APPROVE OF ANYONE FIRING AMMUNITION IN OTHER THAN A FIREARM MADE FOR THAT AMMUNITION.

Jim

Information

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[edlmann]

FWIW, the 7.7 Japanese rimless rifle cartridge will feed and fire in the M1903 Springfield; even the clips will work. The result is a short necked case, but no signs of excess pressure.

That would probably work with .300 Savage, .308, etc. The cartridges headspace on the extractor. I've even heard of a .45 ACP round being fired in an '06 this way.

I thought the base dimension of the 7.7 was larger than the .30-06, and that if you rechambered the 7.7 chamber to .30-06, the bases of the fired cases would be swollen. My reloading data shows both with a base dimension of .471, give or take. This was also supposed to be why you should set back the barrel before rechambering to .30-06.