M1 Barrel Bore Guage Reading

[imntxs554]

What should a bore gauge reading be when testing out your barrel and also should it be level. I havent received mine yet, butt using a 30-06 for now, Thanks

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[JimF4M1s (Deceased)]

I use this. Though I have carbines the almost eat that thing and shoot great. Like anything else, it is a guide not gospel.

[imntxs554]

Thank You Jim, i was searching the book and havent found out about details of the M1 Barrel other than if the the 30-06 Im using right now that if its goes all the way down or close, than the Barrel is bad, but thanks. I've only gotten bit by the M1 bug in July and know the fuction, but the details can be quite contradicting with reading and seeing different conclusions, Thanks

Frank

[Neal Myers]

It is called a "muzzle wear gauge". The gauge pictured is a .30 cal gauge, & will work equally well on an M1 carbine, M1 rifle, M1903 rifle, etc, but NOT on an M14 (because of the muzzle brake). USGI barrels were nominally .300" when new. A measurement of 0 is equivalent to .300", 1.0 is equivalent to .310", etc. The War Dept appears to have accepted new carbine barrels with up to MW=3, while requirements for rifles appear to have stricter because they were used at greater distances. I would expect a carbine to shoot decent groups until you get past MW=5; YMMV.

Neal

[imntxs554]

Thank you , i really appreciate your help

Frank

[CrossedCannons]

USGI barrels were nominally .300" when new. A measurement of 0 is equivalent to .300", 1.0 is equivalent to .310", etc.

1.0 is equivalent to .301". New, bores were spec'd to 0.300"-0.302" (i.e. between "0" and "2")

[Neal Myers]

Oooops, my mistake; Crossed Cannon is correct, I got my decimal places displaced.

Neal

[DaveHH]

Consider that some of the 6,000 round test carbines were simply cleaned and sent out for issue. That gives you some idea of how many rounds these can take and still shoot well. They only use 15gr of powder, about 1/3 of how much a 30-06 uses per shot. Powder burned = heat, heat = barrel wear and erosion.

[INLAND44]

Plus, many damaged muzzles were back-bored about 1/4" during overhauls/maintenance to get back to good rifling and restore accuracy. You simply look/probe for a shoulder near the muzzle.

[imntxs554]

look/probe for a shoulder near the muzzle.? Would this be to see if it was overhauled/ maintenanced ?