.223 77 TMK deforming during bullet seating

You have one of three problems.

Too much neck tension, the interference fit
Too much friction from clean brass
Too much compression on the powder

The first two can easily be fixed. The third I would just avoid, when you get that compressed you start getting wild runout pretty quick.

A perfect fit stem might help but probably isn’t the answer.
 
You have one of three problems.

Too much neck tension, the interference fit
Too much friction from clean brass
Too much compression on the powder

The first two can easily be fixed. The third I would just avoid, when you get that compressed you start getting wild runout pretty quick.

A perfect fit stem might help but probably isn’t the answer.
It's not a compressed load; it was new Hornady brass, and I sprayed it with One Shot the day before loading. However, I'm wondering if I didn't apply enough or if the coating wore off. Only the TMKs had the ring; the ELDMs didn't. I'll do another load this weekend and chamfer and deburr the necks to see how it goes.
 
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