Shooter,
A 12" (slow) barrel with a small case like Grendel (also slow) represents a handicap requiring offset by careful choice of powder and bullets. Do this by choosing the lightest bullets and fastest powders. Something that will burn as much as possible before the bullet exits. The compromise between velocity and powder burn will see about 5-10% unburnt exiting the barrel, but there's nothing you can do about that without lowering the velocity even further.
I assume 'temp stable' means least variation of velocities between night and day, winter and summer - so single-based powders. The main manufacturer of mostly available single-based is ADI, sold in the US by Hodgdens (from slowest to fastest: H322, Benchmark, 8208, H4895).
I recommend powders like H322, Benchmark, and 8208, using bullets no heavier than 100gn.
,
Velocities will be about 2,300+ fps for 100gn or lower, and 2,180- fps for 120+gn bullets.
A 12" (slow) barrel with a small case like Grendel (also slow) represents a handicap requiring offset by careful choice of powder and bullets. Do this by choosing the lightest bullets and fastest powders. Something that will burn as much as possible before the bullet exits. The compromise between velocity and powder burn will see about 5-10% unburnt exiting the barrel, but there's nothing you can do about that without lowering the velocity even further.
I assume 'temp stable' means least variation of velocities between night and day, winter and summer - so single-based powders. The main manufacturer of mostly available single-based is ADI, sold in the US by Hodgdens (from slowest to fastest: H322, Benchmark, 8208, H4895).
I recommend powders like H322, Benchmark, and 8208, using bullets no heavier than 100gn.
,
Velocities will be about 2,300+ fps for 100gn or lower, and 2,180- fps for 120+gn bullets.