I am short on experience and medium on book learning. I think OP's quest for 3000 yards with .300 Win mag is questionable. I recently acquired a LH Rem 700 in .300 H&H and I used it for my first foray at 1000 yards. The rifle has a featherweight barrel and a laminate stock. It is unmodified and the only thing I did to it was verify the torque on the action screws.
I mounted a Leupold 3.5-10 X 40mm scope with Leupold bases and rings. I modified the bases to give me 20 minutes down. It was no problem to be on target at 100 yards and with 24 minutes up, and I was on target at 1000 yards.
I do not have a muzzle brake. I was shooting prone with a bipod. I used a Past Recoil Shield and recoil was not an issue. I shot 50 rounds and was more sore from not having shot prone for 25 years than anything caused by recoil. As a side note, one 20 round string in 10 minutes did not cause a POI shift despite heating up the barrel.