.30 caliber bore dimensions

[trekvana]

Hello all-

from what I understand, the groove diameter for the m1 carbine rifling is .308 inches and the lands diameter is .300 (.302?) inches. Are these measurements the same for all .30 caliber rifles?

cheers
-trek

Information

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[bearhunter]

+ or - a thousandth of and inch. Maybe more depending on many things from the day of the week the barrel was manufactured to the mood of the inspectors and how desperately they needed the barrels.
I have a new in grease O3-A3 barrel that measures .3092. It still has the packing sleeve around it, except for the muzzle where I took the measurement. The other 03-A3 I have has a .3085 bore and the low serial number O3 has such a worn bore, there isn't a lot of sense in even bothering to measure it.

[CrossedCannons]

Carbine bore specs were .300"+.002" (lands) and .308"+.002" (grooves)

[jmoore]

Some exceptions to "regular" .30 calibers:

European bore specs for 7,62x51 run a bit smaller. 0.307" bores are normal.

It also depends on how loosely one defines .30 caliber weapons. 7,62x54R- some Finn barrels are normally 0.308" but most 54R runs bigger.

7,62x39
7.5 French
7.5 Swiss
7,35 Carcano- about the only true .30 caliber as the bore on these is nominally 0.300"

[INLAND44]

Yeah, 7.62x39 and 7.62x54 are bigger like the Brit .303 - .310 bore and .311 bullet. But in the context of traditional US .30 caliber bores, they are .308, whether for M1 Carbine or M1 Rifle.

[Johnny Peppers]

On the 1903 Springfield the nominal bore diameter was .300 and the groove diameter .308, but Ordnance allowed a bore tolerance of .2995 to .3015 and a groove tolerance of .3075 to .3095. I would imagine that M1 Carbine barrel tolerances were about the same.
I have a Springfield Armory 1903 barrel with the star gage record card, and the bore diameter is a uniform .3002 and the groove diameter a uniform .3085.