Re: Twist for 338/408 with SMK
In all the .338-.408 rifles that I have worked with, the 10 twist seems to be fine. With the 300 SMK, you will find your best accuracy around the 3200 fps mark. Which is a comfortable load for the brass you have to work with. I have pushed them much faster, at the expense of the brass, but they always shoot best around the 3200 fps area.
I shoot the .338-.408 Imp, Baer's design, which is simialr to the other improved cases.
As for barrel length, I've had them from 28" -36", in my opinion, the 33" barrel seems to work well.
With the 10 tw, I don't think you're "over cooking" them at all.