My understanding is that the difference in caliber marking used to make it easier to export from the US.
I believe this is absolutely correct. It's silly regulations. The 7.62x51 is a designation for a military cartridge, .308 is civilian.
You just can't be importing "military assault weapons
Strangely missing from the SAAMI specs
, is the 7.62 x51.
I looked closely at the 2 cartridges and almost all gunmakers
say you can use either one. And you
So what's the difference???
The 7.62x51 is designed to be used in a machine-gun and has a thicker walled case to withstand the abuse of high cycle-rate fire and being in a 'chain'.
That also meant it had less room for powder and more expensive brass.
When they "civilized" it into the .308 they didn't need the expensive thick brass cases and would prefer room for a little more powder.
The increase in pressure for the .308 was still within the test tolerance for 7.62x51 so why not?
The main point is, the .308 case is less rugged to abuse than the 7.62x51.
So you can't link a bunch of .308 ammo together and feed it to a M60 machine gun. The cases would get bent.
KT puts 7.62x51 on the US RFB's because the case can stand more abuse and is less likely to fold up and break something like, oh I don't know, say an extractor
. Guess which one they would prefer us to shoot with a lifetime warranty on the gun?:headstratch:
In a nutshell: Can we
use either in our RFBs interchangeably? Yes.
But you can't
use .308 rounds to do this