Re: 300 yard groups
My opinion only here. At or below .75" is exceptional for a hunting rifle. .75-1.00" is outstanding and 1.00-1.25 is very good. 1.25-1.5 is normal and IMHO the standard to which a hunting rifle is measured. 1.5-1.75 I can live with but dont want to. 2" is acceptable for very large game such as elk and moose. Sometimes those big heavy bullets can be tricky to shoot well at longer ranges at very high velocities but given the size of the targets, I can live with it. 3" means I take the gun back to the smith or get a new barrel.
These are however only my ideas and opinions. It takes a 1/2 MOA rifle or better to shoot 1 MOA in the field. With different lighting conditions, air densities and other factors it really takes a 1/2 MOA gun or better to hit a 1 MOA target. If all youre getting is 1 MOA at t he range, hitting a 1 MOA target at other distances in other circumstances becomes increasingly difficult. When you have some accuracy to spare, hitting a 1 MOA target becomes much easier. A deer's lungs are about 8". At 800 yards, that is a 1 MOA target. It is good to have a 1/2 MOA or even sub 1/2 MOA rifle to attempt such a shot and that is provided lighting and other factors are good espescially when youre a bit more nervous than on the range.
Just my .02
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.