Group Siz Issue - Neck Tension?

[pbroski]

That's my understanding, but I'm in a similar place scratching my head about couple loads with SDs less than 10fps and tight 4-5 shot groups except for one wild flier 1-2" off average point of aim. Neck tension/interference fit seems like a likely variable. Tough to pin the fliers on anything.

I know what you mean. I also experience wild shots fairly frequently, but I have a hard time believing neck tension is the culprit. I neck turn the brass, which results in neck thickness variance of .00025" or less, and anneal every loading on an AMP annealer using the same Aztec setting, so the necks should be very consistent. I can't see how 9 shots can cluster, then 1 jump so far out based on neck tension variance. (That is as long as there is no donut present. If there is a donut and the bullet is seated into it, then all bets are off.)

I have a sneaking suspicion the true candidate for the discrepancy is actually the bullets themselves. There may be concentricity issues.

An any case, I'm going to pay closer attention to neck tension variance by utilizing my AMP press to track neck tension to see if there is a direct correlation between it and precision.

 

[Harvey_NW]

but I have noticed that batches of ammunition that assemble with very consistent bulletin insertion forces shoot tiny groups. Batches of ammunition that have easy and difficult bullet insertions have more scatter. Annealing has made a difference in that regard for me. I'm not interested in getting a PhD on the topic, but I am interested in shooting little tiny groups. It works for me.

I tested this once and don't believe any of it to be true, just another excuse. I had a bunch of loaded ammo and some of them were chambering with resistance on new components, turned out my hand primer wasn't seating primers fully so they were a couple thou proud. So I loaded 5 rounds with prepped brass at my normal interference (~.004"), and 5 rounds of brass that had bullets pulled and reseated and pressed in like butter with barely any resistance on the press. Also 3 of each were a bullet from a new lot, I was feeling western.

This was the 10 shot group.

 

[Vern400]

I tested this once and don't believe any of it to be true, just another excuse. I had a bunch of loaded ammo and some of them were chambering with resistance on new components, turned out my hand primer wasn't seating primers fully so they were a couple thou proud. So I loaded 5 rounds with prepped brass at my normal interference (~.004"), and 5 rounds of brass that had bullets pulled and reseated and pressed in like butter with barely any resistance on the press. Also 3 of each were a bullet from a new lot, I was feeling western.

This was the 10 shot group.
View attachment 859508

I appreciate your comments. I agree with you that the bullet insertion Force is not a big factor. Unless a bad chamfer is shaving copper off the bullet. I think the annealing helps with case life, and a minor side effect is making bullet insertion forces more consistent. But I did see my standard deviation go up by about 12 ft per second, and extreme spread go up more than 30 when I ran my test.

I have started developing all my loads at 200 and 500 yd, which is as far as I have a place to shoot. So sometimes I may think something is important that doesn't matter one bit do a whole lot of people. I probably need to do a better job of calibrating my comments.