Statjunk, that's a lot of ammo for trial purposes. I sort of agree with BC only I load 10 round of each and shoot 5 shot groups. Also, in order to keep the results of the load fair, I clean the rifle after every 5 shot group to eliminate the varible of a fouled barrel affecting the group and let the barrel cool down between groups and alternate the different loads for each 5 shots. You definately don't want to go shooting 20 rounds or more, especially with the 300 WM. That barrel will get pretty hot and if you have a bedding issue you will see stringing as the barrel heats up.
As for selecting poweders, I refer to several manuals and check velocities. I try to initially use a powder that will give me the most MV and fills the case to just below the neck. I try to avoid powders that don't fill the case enough or result in a compressed charge. Once I find a load that is consistantly accurate, I play with it by increasing, decreasing the charge, changing powders and, if possible, the OAL.
You seem enthusiastic about reloading but take your time. Its better to go out and shoot 20 consistant shots in a session than to blow out those 60 rounds as fast as possible. It should take you the better part of the day to fire off those 60 if it is done properly. Remember to write everthing down either on the target or separate paper. (Load, group size, range weather conditions, etc.) And remember, one tight group doesn't mean that's the best load - what you need is repeatability)
Big - I have a load for you with IMR4064 using 180 gr Nosler Accubonds. I will post it here later when I get home.