I put the Ace #144 in my 452 American. The Spring is actually a Hillman part# 540431-H. It dropped the pull in the 452 from 2-3/4 lbs to 1-1/4 lbs. My Savage Mark II is at 3/4 lbs (12oz) so that put them pretty close. Both are set up for bench-rest so, the lighter weight is what I was going for.