Yotehtr1
Active Member
I was just down at the range this morning to start load development with 215 Berger's in my 300 win mag. What I discovered is much higher velocities than Berger predicted at lower charges. And I saw pressure signs at a fairly mild load in one instance and stopped there. Here's the specifics. According to my comparator my cbto measurement at the lands is 2.871. Berger recommended starting 0.015 off. This made my cbto 2.856 with my comparator set giving me 3.649 total cartridge length base to tip. I'm using once fired federal brass, federal 215M primers, and h1000. The suggested starting load was 70.5 grains at 2632 fps and a max of 74.0 grains at 2772 fps. They used a 26" barrel and so am I. I loaded 11 rounds every half grain from 71.5 to 76.5 to look for pressure signs in my rifle. At 71.5 I matched their max velocity at exactly 2772. 72 grains gave me 2812, 72.5 gave me 2855, 73 gave me (oddly) 2842, 73.5 gave me 2879, and 74 gave me 2917 but with faint ejector marks. All primers were somewhat flat but didn't appear at all alarming and I never got a sticky bolt lift. I then decided to run up with another set every 0.2 grains. First was 72.6 with two shots 2818 and 2836. Second was 72.8 grains with 2842 and 2830. The 72.8 grain load produced very faint ejector marks on one case but not the other. In the first series I didn't see pressure until right about max charge which was understandable and the second set showed up 1.2 grains sooner which was odd. Velocities of the 72.8 charge were in the ball park with the initial 72.5 and 73.0 grain range. What I'm confused on is the much higher than listed velocities. What should I be checking? Generally I've had a hard time matching book velocities let alone exceeding it by a significant amount. I was under the impression seating out longer and increasing case volume would lower pressure but that doesn't seem to fit with what I'm seeing. Sorry for the long read but wanted to be as specific as I could. Temperature today was 32 degrees
