gvnwst wrote:
it is, on the other hand, a shortened, improved version of the -06.
As has been pointed out, that's just not true. Unless you want to call your Ford Mustang just an improved version of a Pontiac Firebird (or vise versa).
how do you think you can get the same performance with a shorter case? you fatten it up, or just straiten out the walls....
As highorder pointed out, there's a chamber pressure difference.
But as you surmised, the 7.62 NATO does in fact have straighter walls than the .30-06, allowing room for more powder and a slightly more efficient burn of that powder.
Sunray wrote:
"...how do you think you can get the same performance with a shorter case?..." You change the powder used. The whole point of the .308 was to take advantage of the then new powders available to get the same ballistics as the .30-06 in a shorter case.
If it was *just* the powder, they could have simply put the "better" powder in the .30-06 case. But as you pointed out, the design of the new 7.62 NATO is what allowed the new powder to be used to better advantage.
Don't forget that there's always a drive for a shorter action length and materials savings in military guns. I suspect if they could've gotten the .30-06 to work just as well with the new powders by simply shortening it to 7.62 NATO length, they would've done only that.
As J.D. Jones once said, "Gentlemen - there are no bargains in ballistics. If you are achieving significantly higher velocities than normal for a particular bullet in a particular cartridge, you have eiither performed a miracle or increased pressures accordingly."
FWIW Jones also said :"The .30/06 is usually considered an inefficient cartridge, but it is difficult to find another cartridge that has been or is as good a general-purpose cartridge than the .30/06. It's record in military, hunting, and target use is unmatched by any other cartridge."