is it 20mm?

Trying so hard not to Google/Wiki it. I want to say 5.56 but to me that doesn't make sense when coupled with U.S. Navy specifically. If I do cave and Google/Wiki it, I won't post the answer.

Same here. I gave up and looked up Navy. I mean, they use the same service rifles as all the other branches.

I mean, a cannon doesn't count as a rifle

Its a former service cartridge now used in a specialized role.

Hint:

Common civilian hunting caliber for brush hunting.

A round used by civilians?

.30-30? This is difficult

7.62x51mm? nevermind, didn't read other posts...I would say the 9x19mm then .

.300 Win Mag?

The .45-70. It's used by the U.S. Navy and Coast Guard to throw lines. Or maybe it's launch lines. I don't know all the nautical terms I was in the Army. Actually it's used as a blank round. No I didn't look it up. Saw it on the Military Channel a few weeks ago.


So what did I win?