It's an AR built on a Noreen 80% lower receiver and a Noreen upper, with a BCA 18" barrel, rifle is a known good shooter with commercial ammo.
It's an AR built on a Noreen 80% lower receiver and a Noreen upper, with a BCA 18" barrel, rifle is a known good shooter with commercial ammo.
Get a 9mm bulge buster or borrow a 9mm FCD and gut it so you can use it as a push through sizer . The BB is probably the best bet as the carbide inserts can be cracked if you need too much squeeze .
A 3rd option would be a .375 cast bullet sizer die and use it as a push through sizer die . It should get you about .380 dia . Assuming we're talking about the 350 basically blown straight 223 case and not some wildcat based on a way shortened 308/×57/06' case with a nominal .473 head and rim .......I can see where getting a .400+ in the chamber might be a problem . The Lee push through bullet sizer is readily lapped up if needed . I would think a 223 case would be just a thumb pressure slip fit through one .
I had a bunch of 45 ACP with the same issue . Stupid autos let the head swell just enough they wouldn't seat in my revolvers .
Your new brass will settle down after a cycle or 2 and you won't need a SB die .
I got a set of Lyman MSR dies...that seems to have corrected the issue, all shells will chamber now.