[neverdem]

What caliber are they likely to be?

The M1 Garand uses .30-06 Springfield ammo. In the right hands, it's good enough for any critter in North America, IMHO.

The M1 Carbine uses a .30 caliber carbine round that's good enough for two legged critters at the closer ranges. Someone must have tried it as a handgun round. I wonder what happened?

These Wikipedia links provide the dimensions of the empty cartridge case in millimeters, i.e. diameter and length, IIRC. Somebody correct me if I'm wrong.

P.S. Wikipedia is not a suitable source for any political topic, but for a technical ready reference, it seems OK.

[Publius6961]

Thank you.

[DuncanWaring]

There are also a few Garands chambered for 7.62x51/.308 Winchester.

[Joe 6-pack]

"Someone must have tried it as a handgun round. I wonder what happened?"

That "someone" was a guy named Bill Ruger...

...Ruger's .30 carbine Blackhawk..."

[Still Thinking]

The M1 Garand uses .30-06 Springfield ammo.

I'm pretty sure there are some .308 Garands also.

[gnarledmaw]

"Someone must have tried it as a handgun round. I wonder what happened? "

AMT Automag III

[tony549]

The 30 Carbine cartridge with FMJ bullets is not very effective against heavily clothed two-legged critters. This was a complaint against the M1 carbine in the Korean conflict. However, use of jacketed soft point bullets changes the effectiveness significantly for the better (ref.: http://m4carbine.net/showthread.php?t=19956). With JSP ammo, the M1 carbine should perform very well for home defense at distances up to 100+ yards.