THIS^ My 11-12lb 300prc has taught me a lot about keeping my form when shooting. As someone who has never struggled to shoot .5moa groups and tighter at 100yd I am embarrassed to say that I have pulled shots up to .5-1moa high at 100yd as I've learned to shoot the big magnums.
To the OP: Get a good rear bag. Sink the rifle hard on the bag every time you shoot, firing hand grip consistency is very important and don't wrap your thumb, consistent cheek weld pressure. Front rest is important also but typically doesn't present issue as often. Buy a good muzzle brake, there are several. I like the Ti Pro 3 on my 300. For my rear bag I'm using the LRO Hunter's wedge with Git Lite along with the bottom bag also. It's awesome. Anyway you probably know all of this already.
Also if you are in a hurry to build and shoot 300PRC right now you will be waiting. Powder is hard to find and quality brass is even harder. Hornady will get the job done to start however. N570, N568/565, RL26. I bought my first jug of N570 3 months before I had a single piece of my build. Anyway it's a awesome cartridge for long range shooting and hunting. If I were only shooting steel at 1000 I'd stick with the 6.5 PRC. But for game, especially elk, at 1000 I pick the 300. Have fun!