Question on why my 243 case necks are cracking

[rockrat]

And maybe the necks have been turned and are thin, and a possibility that the necks are getting overworked between firing and sizing. Whats the neck OD after firing and the OD after sizing with the expander removed? I have seen some dies really overwork the necks

[jim147]

Do you have a regular size die? Are you sure you need a small base sizer? It might be over working the whole thing.

[Tripplebeards]

I did also find that my rcbs trimmer must have loosened up. All my brass was cut short at 2.020”. I grabbed some different RP stampede brass. Annealed, SB sized, and trimmed to 2.035”. I re tested my tightest grouping load and worked it up and and down in .01 grain increments both ways. All the groups opened up with the longer length brass for sone reason. All were still under and inch but not by much. I had one scratch long on each neck after firing.

[centershot]

Do you have a regular size die? Are you sure you need a small base sizer? It might be over working the whole thing.

^^^ Throughout this entire thread this has been my thought. I would try a regular FL sizer.