Keep an eye on your brass

[243yote]

Encountered something new today. Worked up a load using the brass i have been using for about 250 rnds using Win brass and only neck sizing. Well found a load my rifle liked and figured it was time to use new brass. No pressure signs from old brass. No flattened primers at all at even near max loads? Well double checked new load again with old brass and was promising.Used new Win brass. Full length sized,deburred flash holes trimmed and prep like i usually do. So loaded new brass. Weighed powder ,the same AOL. Ran out of primers from previous box so opened new box and started loading. Same type primers WLR. Got to range and started out good but got worse. AFter 5 shots groups starting opening up and had flyers? Let gun cool to ambient temp between strings. Looked at brass after a couple of shots and found flattened primers? Also had 6 primers from old box left before i used new box. Loaded 28 rnds with load developed. 6 rnds did not have flattened primers but the rest did? The new brass felt different when seating bullets also. Old brass would start tight then just almost seem to just push the bullet in? I guess I should have annealed the old brass but did not and do not know how to do that properly. Read a couple of articles but I am still not sure? One article talked about overworking brass and making it hard. I guess i did just that. So what did I learn? When the bullets do not feel like the brass is holding them right and seating them becomes real easy get new brass or anneal old cases. Primers from different lots are different. Well I hope this info helps some other reloaders out there. What a frustrating day but i learned something in the end.

[Gene]

You don't identify the rifle, caliber, bullet, or powder charge.

I do not anneal under 6 reloads. Doubt problem relates to primers. You probably have a different lot of brass, and the interior is just a bit smaller, running pressures up. After they are reloaded once brass should fit snugly in chamber, giving you 1-2% more powder space.

I would neck size that fire formed brass and drop powder charge about 10% below a reloading manual max, then work upwards until you reach a level of accuracy you find acceptable.

[Moman]

+1 on the reply from Gene. I like to buy all components that work for me in bulk and anytime I have to change lot numbers, whether it be powder, brass etc., I rework the load.

[Kevin Thomas]

Yote,
Sounds like a day well spent, and lessons well learned. Bottom line is, whenever you change anything, you've made a change. Components do change, and usually without too much mention. Manufacturers try to keep this to a bare minimum, but even minor lot to lot change can, and will make a difference. Keep your lots separate, and keep your log books up to date.

Kevin Thomas
Lapua USA

[bigngreen]

I had the same thing happen with my 270WSM, I thought I would just load my regular load and go to the range and rock it but when I fired the first couple I got a horrible tight bolt lift and the primers flowed into and filled the primer pocket flat.
What was happening was the new case would set deep in the chamber and at firing the primer would come back then the brass would slam back as it blew the shoulder out mashing the primer and putting a lot of extra pressure back because the case had no traction on the chamber. I think?
Fire formed the rest and then loaded the same load and had the normal stuff going on. It was a stout load and should have though it through but now I know and the wife loves shooting my fire forming load so it works better all way around.