santacruzdave
Member
Got some new bullets. Acme 9mm 135 gr. RN. Without specific load info I thought I'd do some interpolations to calculate a starting COL (plunk test for my shortest leade barrel to follow) and a starting load. My concern is seating depth and the possible resulting over pressure from having the bullet seated too deeply int the case.
The published COL for ACME 145 gr RN bullets (1.10) works in all my 9mm barrels. I measured 10 145 gr bullets and have an average bullet length of .660. I also measured 10 of the new 135 gr RN bullets and have an average of .6136.
So I'm figuring that with a COL of 1.10 for the 145 gr bullet with a length of .660, and a bullet length of .6136 for the 135 gr bullets, calculating the 135 COL should be simple math. Subtracting the length of the shorter from the longer: .660 - .6136 = .046. And subtracting .046 from 1.10 should give me a starting place (1.10 -. 046 = 1.054).
Does this make sense? I don't know why. but 1.05 seems like too low a COL for a bullet length of .6136. Next to make up a dummy round or two and eyeballing resulting space left in the case. Once I'm comfortable with the COL, I can start to figure out some starting loads of Sport Pistol.
Thoughts?
The published COL for ACME 145 gr RN bullets (1.10) works in all my 9mm barrels. I measured 10 145 gr bullets and have an average bullet length of .660. I also measured 10 of the new 135 gr RN bullets and have an average of .6136.
So I'm figuring that with a COL of 1.10 for the 145 gr bullet with a length of .660, and a bullet length of .6136 for the 135 gr bullets, calculating the 135 COL should be simple math. Subtracting the length of the shorter from the longer: .660 - .6136 = .046. And subtracting .046 from 1.10 should give me a starting place (1.10 -. 046 = 1.054).
Does this make sense? I don't know why. but 1.05 seems like too low a COL for a bullet length of .6136. Next to make up a dummy round or two and eyeballing resulting space left in the case. Once I'm comfortable with the COL, I can start to figure out some starting loads of Sport Pistol.
Thoughts?