The first-round flyers were nagging at me, so I did a quick test with dacron fill to see what might happen.
I loaded ten rounds each of 36, 37, 38, 39, and 40 grains of IMR4350, still using the 311466 bullet as before, and each round had a small dacron tuft added. There's not much room in a .308 case when forty grains of bulky powder is installed, but I wanted to try dacron just in case there was enough powder movement to make a difference. These same charges WITHOUT dacron were among those which gave the first-round-flyer results in the previous shooting.
Another possible factor (I thought) might just be all the crud, sludge and corruption which had built up in the action over the previous hundreds of rounds, and which just possibly could be making the bolt lockup slightly different when closing from the hold-open catch instead of rebounding off the back of the receiver. These latest loads were fired from the CLEAN rifle, as described in my last post. Functioning was flawless, if I have to say it.
Nope!
The groups stayed just about the same as they were without dacron, and the first-round flyers are still evident. In a way, this is a bit of a relief, since I really wasn't looking forward to using dacron in each of the hundreds of rounds I expect to be loading when a final load is determined.
Back to the drawing board. I'll try another bullet design in the next attempt, I do believe.