@SPEvo112 The first iteration of the .280 British circa 1949-1951 was a 7x43mm case. Fired a 130 or 140 grain bullet at 2400-2600 fps (velocity was increased during its use). It is notable for being used in the first trials FAL rifles.
The .280 (7x43) was a farmer who was inconspicuously strong from doing real work all day, while 6.8x51 is a roided-out monster who will die at 34 from a heart attack.
A note to FFLs: While it is illegal to remove a serial number, guns made prior to 1968 are not legally required to have them. You don't need to make one up. A Remington Berthier does not actually have serial number "87654".
@RyanMcbeth@AJSovine But the same designation was also used by the Air Force in the 60s for the XM-177, the original Colt carbine version of the M16. So if you search for "GAU-5/A" you will find references to both, and they are not the same gun.
@RyanMcbeth@AJSovine Now I really wish I'd done a video on the modern GAU-5/A...but FYI for folks, the designation has been used twice. The current aircrew survival gun is basically a shortened M4 with a detachable barrel and folding grip for stowage. (con't)