Originally Posted by Erik Kiser
What could one expect from an improved 375 RUM case with a 350-370 gr bullet or would it be better to start with a 378 Weatherby case. I'm just thinking what is possible without going all the way to the Cheytac case. As you know an RUM case would allow a M 700 action, is 3000 fps possible using an improved RUM case and a 350 gr bullet with a shorter bearing surface(Berger'ish)
In my testing comparing the 338 cal 300 gr SMK to the 375 cal 350 gr SMK in both my 338 Allen Xpress, 338 Allen Magnum, 375 Allen Xpress, 375 Allen Magnum. The 338 calibers will drive a 300 gr SMK roughly 50 fps faster then the same case capacity but with the 375 cal driving the 350 gr bullet weight.
The 350 gr SMK has a relatively short baring surface compared to the 338 300 gr SMK so I do not really see the baring surface being shortened all that much if Berger makes one, especially if bullet weight is increased to the 370-380 gr range.
The 375 AX will get 3000-3050 fps pretty comfortably in a 30" barrel length. Now that is on average, some will run a bit more, some a bit less. Now, a 375 RUM Improved has a case capacity roughly right between a standard 375-338 Lapua and my 375 Allen Xpress so I would say absolute max velocity with the 375 RUM Improved would be in the 2950-2975 fps range with 350 gr SMK. With a 370 gr bullet weight, I would say 75-100 fps slower.
Now, keep in mind how long we all were playing with the standard 338 Edge driving a 300 gr SMK to 2850 fps and it killed a hell of a lot of big game at some very long ranges.
IF we get a bullet with at least the same BC as the 300 gr SMK which should be easy to do, add in the larger bullet diameter, higher kenetic energy payload and in a bullet that expands reliably, the 375 cal will be a far superior bullet for long range big game hunting.
Basically it all comes down to getting a bullet with BC at least into the G1 +.8 range with a design that will allow top speed for bullet weight and also expand reliably.......