I was once in the same boat, I used a .300wm in a t3 for my mountain rifle. My personal preference, was the .300 was to long for my liking, and was just a matter of time before I split my eyebrow open due to steep angle shots and heavy recoil. I switched out to a light weight 6.5x55 in a t3, and have been loving it. It does limit me though, FPS vs bullet performance at longer distances. For that reason I’m stepping up a little to the PRC.
The .300 is a excellent mountain cartridge, if a guy has no issue holding into it. For my best shooting, I find the less “hold” I have of my rifle, the more consistent I shoot. My old .300, I had to get a good grip on to hold it down, which in turn declined my accuracy.
Just what led me to the PRC.