Im having a little problem

[DJS]

I built an AR in 6.5 grendel a year or so back, long story short it turned out the barrel was bad so the end of last summer I bought a different barrel, I didnt have much time to mess with it after the barrel swap other than get a quick decent load worked up for hunting season, I havent messed with it after that until now that the weather is getting warmer, I had a bunch of brass that had been run through the old barrel, then resized and some reloaded and run through the new barrel, the brass from both the new and old barrels were mixed together and Im now resizing the whole lot and finding some brass are running through the die ok and some are running though the die hard and coming out with a prominent ring around the base, theres no other damage to the brass during resizing, Im using a lee resizing die and Im thinking the problem brass is what was run through the new barrel and this new barrel might have a chamber that isnt the same spec as my die and after the brass fire formed to the chamber its now causing this problem during resizing, I didnt have this resizing problem with the old barrel and its the same brass, anybody have any opinions or suggestions on whats going on or what to do about it?

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