Re: Data for ALL Cals Ackley Imp
280 Ackley Improved...
This is my first go-around with an Ackley round.
Brux, 26", 1-9 twist, Oehler Chrono 8 feet from muzzle.
1200' elevation, 97-105 degrees, about 25% humidity.
Fire-forming load, 280 rem brass, CCI 200 primer, H4381SC, Hornady 162 BTSP interlock bullet. Velocity is average of 5 rounds.
51 gr, 2472 fps, SD: 19
52 gr, 2515 fps, SD: 20
53 gr, 2591 fps, SD: 27
53.5 gr, 2604 fps, SD: 30
54 gr, 2641 fps, SD: 30
54.5 gr, 2680 fps, SD: 17
All the loads shot within 1 MOA except the 53 gr load and I had a lot of barrel mirage. I'm not happy with the SD numbers, but it is fire-forming so.....
I resized the 280 AI brass, bumped shoulder back .002" I decided, for no particular reason to try the Sierra 175 SMK. I again chose H4381SC from recommendations by others. I decided to jump these .020 and will get closer to the lands as I go. I also loaded 5 differing charge weights among the 50 rounds, but I loaded 5 rounds with a 200 primer and the other 5 with a 250 magnum primer for each charge. 1200' elevation 35%humidity, 97-103 degrees. Oehler chrono 8 ft from muzzle.
55.0gr, 200 primer, ES: 41, Vel: 2641fps, SD: 20, group: 0.679 MOA
55.0gr, 250 primer, ES: 34, Vel: 2673fps, SD: 12, group: 0.593 MOA
55.5gr, 200 primer, ES: 24, Vel: 2684fps, SD: 10, group: 0.636 MOA
55.5gr, 250 primer, ES: 51, Vel: 2693fps, SD: 20, group: 0.951 MOA
56.0gr, 200 primer, ES: 29, Vel: 2697fps, SD: 13, group: 0.468 MOA
56.0gr, 250 primer, ES: 33, Vel: 2724fps, SD: 13, group: 0.593 MOA
56.5gr, 200 primer, ES: 13, Vel: 2734fps, SD: 05, group: 0.543 MOA
56.5gr, 250 primer, ES: 71, Vel: 2770fps, SD: 27, group: 1.201 MOA
57.0gr, 200 primer, ES: 35, Vel: 2755fps, SD: 13, group: 0.784 MOA
57.0gr, 250 primer, ES: 52, Vel: 2781fps, SD: 21, group: 1.097 MOA
The 57.0gr load looks like the primer is starting to flatten, but no other signs of pressure. What velocity should I be getting with the 175SMK? I was thinking tops would be around 2875fps... Thoughts?
I was thinking of doing the same type of test, but jumping the 175SMK .010 and beginning with 56.5 and work my way up to around 58.5 or until I see some pressure signs... Thoughts?