Originally Posted by Chas1
Chad, how fast would that 7mm-338LM with a 168 gr smk?
The Sierra .284 175 would have a lot better BC than the 168 and would be my choice out of a super charged magnum. Out of the same parent cartridge, the GS 177 could be launched 300 fps faster, or more, with as good or better a BC and it's terminal performance is both better and more reliable, not to mention an expansion velocity of 1600 fps.
A rule of thumb I use to compare 7mm calibers to the 30's is a 7mm will launch 160 gr bullet about the same speed as a 30 will launch a 180 bullet. i.e., 7 WSM vs 300 WSM or 7 RUM vs 300 RUM, etc.,. That's just a very general rule of thumb for rough comparisons.
The 7mm high BC bullet selection is very limited IMO. The top end of the commercially available bullets, which is the 180 Berger is velocity limited unless you go with the "target" version. ATM, my top choice for a 7mm hunting bullet is the 150 E-Tip, followed by the 160 AB.
For deer size game, the 7mm is a great cal. But for elk, it's a very good idea to get as much of an edge as you can. The 7mm can get the job done, the 30 cal can do it better, especially @ 1K.
For the OP's requirement of a 500-1K elk cartridge, the 30-338 LM fits very nicely in his Mark V action, IMHO and the barrel will last twice as long as a 7mm-378.