So, baby steps.
Got the 24", 1-10", CZ .30-06 to the range yesterday for my first .30XCB experiment using H4831SC and 2500+ lube. Bullet alloy was 1 part Lyman #2 to 2 parts linotype at about 19BHN. Lapua brass. Primers were Federal Gold Medals. Empty space in the case loosely filled with Dacron.
Starting charge was 38 grains and worked up in steps of half a grain. Three shots fired for group at each step over an Oehler 35P. Nine shots fired, then the barrel was allowed to cool back down to "room temperature" (a fairly cool, windy day in the '60's).
For the less intense 38 to 46.5 grain charges, we used our "2nd quality" bullets with the lumpier sprue cuts. These took us from a 3-shot average of 1754 up to 2222fps. Worth noting is that combustion of the propellant was not really complete until we reached 43 grains. Prior to that, there was a significant trail of unburned granules left at the 6:00 position of the bore. None of these loads had trouble staying in the 6" 9-ring diameter of an SR-1 target and we had numerous instances of two in one hole, and plenty that would hold the 3" 10-ring.
We hit the pretty-based "1st Quality" bullets at 47 grains. Best group for the day was about 1.5" inches at 2267 fps with the 47.5 grain charge.
The wheels started to come off the wagon shortly thereafter. 50 grains took us to 2374 fps and it was decided that accuracy had left the building. At 51 grains and 2415 fps, we experienced the first bullet completely off the 10" SR-1 repair center. 52 grains got to 2481 fps, were spread out at over a foot. Metal fouling was beginning to appear on the crown over the last several groups. There was an impact mark from a gas check on one of the chronograph's sky screens, so definitely experiencing some of the previously-discussed integrity issues
We were intrigued enough by the lower speed accuracy and the earlier results from Dad's '95/Krag to heat treat and water quench some of the older WW+2% versions of the bullet. Going to run these from about 46 to hopefully 58 grains to see what transpires. Next range adventure hopefully in a few days.