Regarding the 300 mag.

Yup....I have a friend that hunts elk with his 300 and he has never been really thrilled with the groups he has shot. They were OK, but not what a 300 is really capable of. I took him over a box of BR2 and he loaded up some of the same loads that he typically used, but just changed out the primer....he said it was a totally different gun....shoot the coconuts off of a gnat at a 100 paces now as he put it.........LOL

Lots of loaders disagree with me on not needing a magnum primer for the big magnums...but then I doubt they have really put the BR2 to the test.

I know this. They work for me, make VERY accurate loads at good velocities WITHOUT jumping up the pressures I used to get with magnum primers. My buddy explained that the BR2 produced a more progressive burn than the magnum primers. ie...instead of a really large hot flame to ignite the powder it was a longer burn that gave more even ignition over a longer period of time, thereby keeping initial pressures down.