Nothing at all wrong with a 300 WM (I elk hunt with a 300 WSM). However, the magnums aren't pleasant to shoot or if they are (i.e. braked) they are VERY loud. Make sure you can actually shoot your rifle from a variety of shooting positions under pressure (see Forms Equipment vs Practice thread for a good drill to help you). My 300 WSM started out braked. It now wears a TBAC Ultra 7 as the noise was very unpleasant in a hunting situation. I shoot it from different positions every chance I get. Also, rookie season OTC elk hunting is TOUGH. If you aren't going with a seasoned veteran who knows the area you are hunting, the odds are against you having any success. Colorado OTC success rates aren't great. My first year was tag soup but I learned a LOT about elk and elk hunting. My second year I tagged out on a nice OTC 6x6 bull. I'm still no expert but I now know what to look for and I have a better idea how to approach things. Good luck to you.