I had a Ruger 77 tang safety rifle in 280 Remington "improved" to 280 A.I. back around 1990. The rifle is long gone, but I still have the barrel. Also gone are my load notes.
I recently acquired a new 280 A.I. rifle, a Savage 100 Hunter from a guy here at the 'fire. It has a 5R barrel. I haven't shot it a lot, but enough to see that it is quite accurate. I have been busy fire-forming brass and shooting moderate loads. I'm not looking for 7mm Remington Magnum velocities.
That said, has anyone tried RL-26 in his 280 A.I.? I recently loaded 61 grains of RL-26 under a 150 grain Nosler Partition. Velocity was only 2,860 fps, practically a starting load. The Lee loading manual velocities seem to match my velocities pretty closely. Nosler velocities are higher than mine with similar powder charge weights and the same Nosler bullets.
