26" Bartlein, 1:7.25.
108gr ELD-M
Virgin Peterson brass
CCI 450
H4350
2.236 CBTO ~ 2.796 OAL (factory ELD-M measurement)
Started load development on my new 6CM barrel for my AT-X this afternoon. It had 40 rounds through it before I started, so I expect that it will speed up a bit...but I was pretty disappointed in the velocities.
This was my first time using Peterson brass. Previously I had used Hornady, and I had heard that the Peterson stuff had less case capacity. Out of an abundance of caution, I had used Nosler's load data and not Hodgdon, as they have a 2.1gr disparity for H4350. Being that I saw zero pressure signs, I think I will step it up a touch next time.
I didn't get the ES and SD that I was hoping for either, but it may just take a powder change. I just got spoiled shooting 6.5x47s where everything works.
Accuracy was pretty good though. If I were content with 6BR performance, I'd test the 38.3gr charge again and if it held up a few more times I'd call it good.
^ That was my opening group, and I was pretty excited. Unfortunately the ES and SD opened up, which may be related to my cheap-ass chronograph. I got a couple errors, and then set it lower a couple inches where everything seemed to read again. FWIW, it gets me to within .1 mil usually at 600 so it can't be too shitty.
Highest charge of the day (Nosler max) produced a decent group too. I think it might creep over 2,900 after another hundred rounds or so on the barrel...but that ES though...
Between those were some acceptable groups. I had one flier, but it broke clean, so I figure it just isn't a happy spot. I also tried toying with my zero after the second group, and my first shot on group 3 took the stupid sticker off...so I had to shoot at the bullet hole. I went back down .2 for groups 4 and 5.
Next: I'm going to work up another half grain or a touch more. I'm still not real comfortable with my knowledge of Peterson brass in regards to case capacity.
The whole target for today:
If any of you have some experience with Peterson brass, I'd be glad to hear what kind of charge weights you were/are using.