Ok got a few days of testing done with the range all to myself with great weather. I did a lot of the strain gauge data logging straight into GR Trace, and I wish I would have just had the data go straight into the Pressure trace software as I just spent the last day and a half figuring out how to calibrate the chamber pressure readings. That's why it took some extra time to get the info up. So I'll just start with the parameters.
6000' Altitude (Mountains of Colorado)
Temp 59f
Baro 29.53
No wind
102 yards
30" Krieger- heavy marksman 1.250-.90 / 8.750 twist rate / roughly 900 rounds through it
Kelbly Atlas Tactical
XLR Element C-6 buttstock (fully weighted)
Triggertech Diamond pro
Hawkins Precision one piece mount
Tract Toric 4.5-30x56
total gun weight in current form 21 lbs/ shooting prone position
Using Magnetospeed V3 for chrono
Pressure Trace2 strain gauge for chamber pressure measurements
ADG brass I think 8-9 firings to date
Trimmed 2.565
Case volume 93.5
Neck turned to .014 thickness
Annealed after every firing
Never case cleaned or tumbled, But always wiped down and primer pockets cleaned
Neck tension 2.5 thou
COAL: 3.685
CBTO: 2.940
Primer seating depth: .002
Bullets: Berger 184gr F-Open Hybrid Target (All other tests have been 190gr LRHT, but I couldn't get any more at the time)
Primers: Remington Magnum Large Rife/ sorted by cup thickness into .001 increments. 6 thousandth's variance in the box of 1k. F-ING 6! All cups used measured .132 (Again, the only magnum primers I've been able to get. With some of the other powders I have done load testing for I have also tried CCI Large Rifle and CCI #34 NATO).
Powder: For this test Retumbo. I have also tested H1000, Win Sta-Ball HD, N570, N565. I did not run up to max pressure on this test, but I did run 75, 75.5, 76, 76.5, 77, 77.5, and 78. No signs of pressure at 78. Each group was 5 shots except the final group of 80gr because I'm a case short.
I think it's important to say also that in a few of the groups I had a strange load where one single bullet would be significantly higher or lower than all of the others. as an example the very first shot of group 1 was 20 fps faster than all of the rest, so it shows an SD of 10.5 and ES of 25 but removing that one odd round makes it an SD of 2.2 and an ES of 5. Same with the last shot in group 2 which shows an SD of 18.8 and an ES of 46. removing that final shot would make the SD 5.8, and the ES 11. The final group of 78 grains shows a ridiculous SD of 35.6 and an ES of 76, but removing the bad round shows an SD of 9.3, and an ES of 17. I'm assuming it has something to do with my reloading, but I haven't pinpointed the problem. I'm not going to make any excuses or apologies, I just thought that with that large of a swing that it was worth letting whoever reads this, know not to misinterpret what might look like a bad load charge weight when despite my human error, its actually great. some charge weights were just totally awful regardless numbers wise, and didn't seem to me that they were worth investigating any further. Those two groups were 76.5 and 77gr.
75gr
max 3035 (3055)
min 3030
avg 3032
SD 2.2 (corrected)
ES 5 (corrected)
75.5gr
max 3068 (3103)
min 3057
avg 3032
SD 5.8 (corrected)
ES 11 (corrected)
76gr
max 3097
min 3075
avg 3085
SD 10.4
ES 22
76.5gr
max 3163
min 3095
avg 3128
SD 32
ES 68
77gr
max 3163
min 3030
avg 3032
SD 2.2 (corrected)
ES 5 (corrected)
77.5gr
max 3035 (3055)
min 3030
avg 3032
SD 2.2 (corrected)
ES 5 (corrected)
78gr
max 3159
min 3142
avg 3148
SD 9.3 (corrected)
ES 17 (corrected)
I'll add more later and if anyone needs detailed info I'm more than happy to share. Hope this helps.
are you guys talking about necking down 300PRC to 7mm? Because my dyslexic brain assumed 7mm PRC 
sorry .
