Old thread but relevant.
Just getting into LRP and picked up a RPR in 300WM with 26" barrel. Never had anything bigger than 30-06.
Been reloading since 1980 (started with lee loader LOL) Most of my reloading has been Hunting (less than 150 yards) and blasting (plinking).
So I lucked into some Federal LRM primers.
Started ladder loading with 208gr ELDM and N165 powder. Velocities in the 2700 range, SD in the low teens, good groups(1.0" @100yrd)
On a whim I switched to CCI 34 primers and same load shrank to 1/2" and SD of single digits!
I am trading a buddy my magnum primers for his CCI 34's