I am starting a new build of a 300 WSM on a trued Rem 700 LA. I would like to think that with the LA magazine and the ability to seat the bullets out further to maintain/increase powder capacity I can effectively get higher velocities with the longer and heavier bullets. Any suggestions on how much additional leade over SAAMI specks would be beneficial? I would like to shoot 168 - 190 gr bullets.

I have set up a dummy round with the 175 gr Barnes Long Range TTSX. Easily fits my LA magazine and COL is 3.153". Too long is rifle is throated properly. Base of bullet comes to base of neck.

If you are using a long action, why go with a short mag cartridge?; just go ahead and go for the 300 RUM.

I would like to get rid of the belt and have an efficient cartridge. The RUM is too overbore for my taste.

At your 3.15 you are gaining about 8% net powder volume based on QL. So a basic 06 type case gives about 1% velocity for 4% capacity. A larger case will give less. So going to your max you can gain 50-60 fps.

If you are going long and using a LA why not take it long enough to handle your longest planned bullet. Just remember shorter bullets will end up with a good jump to the lands.

The mono-metal bullets need to be loaded a ways off the lands (usually .040 to .050"), if that is what you intend to use in it, so that needs to be factored into your length.

Good point and thank you.