Large vs small primers

[StoneHendge]

I have extensively used Starline 7.62x39 brass, primarily to use up an oversupply of LRPs in a tight primer market. I've had great accuracy and success, but I don't chase velocity since I use them for practice rounds. What I have found is that with the larger spark, peak pressure comes a little earlier and thus, not as much powder can be used. It seems that the faster the powder, the earlier the (relative) peak. The end result is having to accept lower velocity, which is fine for me since paper at 100 yards doesn't care what the velocity is and steel out to 500 remains well within reach. Using milder loads, some primer pockets start to go around 5-6x, but loss of brass resilience in the neck (and hence neck tension) is what sends most brass to the scrap yard (note that I don't anneal).