Federal .223 cases have the softest brass and a thin flash hole web.

Lake City 5.56 have harder brass in the base and a thicker flash hole web. Meaning longer lasting brass and thighter primer pockets.





When you have brass flow into the ejector it means you are over pressure for that brand of brass.

I buy bulk once fired Lake City 5.56 cases and to keep things simple thats all I shoot from my AR15 rifles.

The problem you are having was well documented at ar15

Below a 2 inch rod was used to measure the thickness of the flash hole web. And the cases with thinner flash hole webs were rejected for reloading. I have new factory loaded once fired Federal cases with over sized primer pockets.



When seating primers any primer pocket that is not tight I use a Lee primer remover tool. If I can move the primer with just finger pressure the case goes into the scrap brass bucket.



How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests << Daily Bulletin

Bottom line, I only use Lake City cases or commercial 5.56 cases made for the military made to military standards.

The photo below was from AR15.com and the poster said he didn't worry about loose primer pockets and would replace the bolt when it got bad enough. (not very smart)



The only range pickup brass I use are once fired Lake City case that still have a crimped primer.

.223/5.56 - Cleaned, Deprimed & Swaged - LC Only - 500 Pieces $54.00 free shipping.
.223/5.56 Cleaned, Deprimed & Swaged Lake City Brass 500 Pieces