Proper cartridge head spacing for AR10 questions

So, I grabbed a different brand brass cases that I just annealed about a month ago and then FL sized I’m my standard 243 die with it turned down a quarter turn past flush.

I took three of these cases and ran them through my SB 243 die leaving the case turned up where I had it sizing my federal case shoulders at 1.625”. I ran all three frontier cases through the SB die and measured. All were 1.624”. I turned the up approx another 1/2”of a turn and ran the same cases that measured 1.624” through my die again.. All three case shoulders grew to 1.625”. So learned a lesson, if i run them through my SB FL sizer and make them too short for headspace clearance I still can make my case shoulders expand and grow again if I turn my die up more. I figured when I pushed the shoulders down I would not be able to get them to stretch again till firing and would have to deal with the shorter headspace cases. This explains why when i size a case and then when I run it through the sizer there is still some felt resistance from spring back.
 
Last edited:
Must have been a fluke as the rest of my brass didn’t “grow” like the couple ones did the other day when I readjusted my FL SB sizer out. I’ll have to load and shoot them to expand my casings again. At least I’m on the right track now. I guessing the original cases grew being they were freshly annealed at same time?

I resized a lot of casings given to me that the shoulders are about .008” shorter. It will give me an excuse to load them all up and brake my barrel in along with getting use to shooting my new 243 AR.
 
Last edited:
Back
Top