Re: 240SMK with 300 RUM
220 SMK I can get about 2950 fps in the 26 in. tube, and I'm sure I'd get less with the 240gr, I just haven't tried it in my 300 Ultra yet.
I think 3000 fps is pushing things hard in a 28 in. tube. A 338 cal. and you could get away with it, 30 cal... I'm "guessing" is topping 75,000 psi or better if you do.