… The rifle was built for 120gn bullets and won't feed the 100 grain ones…
Bullet weight has little to do with feeding, bullet shape and seating depth do. Is the OP looking for highest velocities, best accuracy, or what? Reloder 7 and IMR4198 are pretty fast for decent velocities with 120s in a .250AI. Sierra doesn’t list anything faster than H4895.
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