I have heard some say that the 300 grain will not stabilize unless pushed fast but I have no experience with the 300s so I do not know.
I use 240 xtps in both my ruger redhawk and my 1894 marlin and are easier on me and my guns. 23.5 grains of H110 and the 240xtp gives me 1300 fps out of the 4" redhawk and 1750 fps out of the 20" marlin. At one time I seen a chart that showed the working speeds for the 240 xtp to reliably expand and if my memory serves me right the 240 works from 700 or 800 fps up to 1750 fps but I could be wrong. If I was going to use anything heavier than the 240s I would go with a flat nose cast but some are iffy in the marlin. Also if you shoot 300s in the marlin you need to seat in the top groove, here is a qoute from midwayusa.com reviews,
This bullet has two cannelures, and the technical specs according to this web site advise to use the bottom (rear) cannelure for Magnum loads; do not do this if you plan to use them in a lever action, because the bullets will be too long and will not cycle through the action. This happened to me at the gun range, and I had to remove them from the front end of the magazine tube. I did load a few of them one by one, and they shot OK, but I reloaded the rest deeper using the forward cannelure. The difference is in the OAL 1.75 vs 1.6.
Hope this helps.