cracked case mouths

so i shoot a little bit the other day after installing some new scope rings to get sighted back in with the coyote gun. shot a batch of loads i put togehter a coupe months ago. i noticed some of the case mouths were cracked just at the tip down about a 1/16th of an inch or so. this is out of a same batch i shot a few weeks ago with no cracks. these loads are charged almost 2 full grains below max charge weight, bullets are seated around .0020's off the lands with no crimp. there were no flattened primers or other signs of over pressure. has got me a little stumped. i had these rounds out with me on some very cold days chasing coyotes this winter. they are hornady brass, cci br primers, sierra 60gr. varminters with 45.5 gr. of imr4350. is hornady brass a little more brittle than others? should i anneal these cases before i resize? like i said the first 10 out of this batch did not crack but the last 10 i shot this last weekend did. seems weird. the only change to anything was the the new rings on the gun. ???

the hornady cases ive been dealing with are too soft already

The rings had nothing to do with it. My best guess would be some of your brass needs to be annealed and just as well do it all while you are doing it. I would also junk the split stuff unless i could trim it back behind the split and still stay in spec but with my 308 i just junk brass when it does something funky like that cause i have so much of it. No use in taking a chance with the neck spliting and causing me to drop a point at a match.

Gary

i realize the rings had nothing to do with it. just kinda throwing out there. thank you for the replies and advice i appreciate it.

how many times has this brass been reloaded?

1st time reloading these cases, i was mistaken also they are remington cases. i did how ever measure them and they are about .015" longer than the trim to dimension in the manual. i have bought a trimmer since. see if that helps

Try to insert a new bullet, by hand, in one of the fired cases without a split neck. If your cases were to long and went into the lands your neck may have not had enough room to expand. With this tight bind in the neck pressures will go way up and produce split necks. If the new bullet can be inserted in a fired case and easily removed, you know your loaded round is still in the freebore and not spiking pressures.