The 7 Rem mag necked up to 375 has been done. The chambering often called the 375 Taylor aka 375/338 win mag. Very easy to make by necking up 338 win mag brass. Can be loaded to shoot a 300 gr bullet as fast as 2490 fps. Shoots the 260 accubond up to 2775 fps. This is close to 375 H and H performance. It can also be loaded down due to the cartridge's small size. Powders like Varget and RL-15 work well in this chambering.
I had an Interarms Mark X with a 21" douglas barrel and a McMillan stock. Suggested to my gunsmith to first use a 338 Win mag reamer followed by a 375 H and H reamer. It worked and made a good chamber.
While I used it to Kill two elk with a 260 gr accubond @ 2775 fps, I developed a few other loads:
64 gr of varget, 300 sierra, vel 2490
59 gr of RL-15, 260 accubond, vel 2325
66 gr of RL-15, 260 accubond, vel 2675 KO FACTOR 37
68 gr of RL-15, 260 accubond, vel 2775 (max in my rifles)
75 gr of RL-15, 235 TSX, vel 2990
235 Speer, 72 gr H4831, vel 2325
220 gr hornady flat nose 70 gr of Varget 2770 fps
I bought a basic two die set from Redding.
Good luck with your project with whatever chambering you use.
I had an Interarms Mark X with a 21" douglas barrel and a McMillan stock. Suggested to my gunsmith to first use a 338 Win mag reamer followed by a 375 H and H reamer. It worked and made a good chamber.
While I used it to Kill two elk with a 260 gr accubond @ 2775 fps, I developed a few other loads:
64 gr of varget, 300 sierra, vel 2490
59 gr of RL-15, 260 accubond, vel 2325
66 gr of RL-15, 260 accubond, vel 2675 KO FACTOR 37
68 gr of RL-15, 260 accubond, vel 2775 (max in my rifles)
75 gr of RL-15, 235 TSX, vel 2990
235 Speer, 72 gr H4831, vel 2325
220 gr hornady flat nose 70 gr of Varget 2770 fps
I bought a basic two die set from Redding.
Good luck with your project with whatever chambering you use.
