Re: 300 RUM/ 220MK\'s??
On average, RL-25 and Retumbo are very similar as far as charge weight and velocity. It will largley be determined by lot numbers though. If you have a slightly slower lot of RL-25 and a slightly faster lot of Retumbo, you will get these differances and vice versa. One thing though, it seems as if Retumbo beats up my brass alot more than RL-25 at the same velocities.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.