I had something similar happen to me but it wasn't .250 it was .100 deeper. I measured again and found the true dimension was .100 shorter. As you know, start seating depth .020 short of that for the satterlee powder ladder test. My guess is that you were into the lands causing the pressure.Hi all, I'm looking for guidance on the correct usage of the Hornady tool after using it to load some rounds recently that ended up with flattened primers:
I used the OAL gauge with a generic 6.5 CM modified case to measure the CBTO in my Savage 12 LRP rifle. I inserted the body into the chamber until it rested against the shoulder and then pushed in the plunger stopping at the first sign of resistance. The CBTO measured 2.0000" on average using my mitutoyo digital caliper. On my 5th measurement (using the same bullet) I wiggled the plunger a little after initial resistance and the bullet slid in an additional 0.25" before stopping again. I did not force the plunger, just rotated it and the bullet slid in further without any pressure. I repeated this another several times with the same results. The CBTO measurements afyer wiggling were an astonishingly consistent 2.2500."
I loaded 100 rounds using new Lapua LR brass, Berger 140 hybrid target bullets, H4350 powder, and CCI BR-2 primers seated at 2.2300" (0.020 less than measured CBTO) and cycled a number of the rounds without feeling any resistance or seeing markings on the bullets. I measure COAL before and after cycling and it did not change.
I took the rounds to the range and had very good accuracy with reasonably low SD measurements (8.6 fps at 41.5 gn and 9.0 fps at 42.5 gr of H4350). The issue was that all of the primers were flattened which makes me wonder if I had seated into the lands of the rifling using the 2.2300 CBTO length?
Should I have used 2.000" CBTO as my seating reference? COAL for my loaded rounds was 2.9375" on average using the 2.2300" CBTO seatinng depth.
The online Hodgden reloading resource lists 40 gr of H4350 as max with a Hornady 140 gr bullet, but Hornady ammo boxes indicate (or at least they used to indicate) that their 140 gr A-Max rounds were loaded with 41.5 gr of H4350. I had heard that earflier versions of the Savage 12 LRP CM rifles had tight chambers resulting in popped primers, but my gun is new production so I wouldn't suspect that this is the problem either.
Thanks for your thoughts.