I hope my story helps
In 2002 I paid for a Jet 13x40 lathe and Clausing mill and put them in a buddy's garage.
My plan was 4 of us were going to build Mausers rifles and go deer hunting.
I got 4 Lothar Walther light varmint barrels and a 257 Roberts Ackley reamer from Brownells.
My rifle was first.
We used a new piece of Winchester 257 Roberts brass as the headspace gauge.
When I shot the rifle, the brass broke.
It seems the firing pin pushes the 257 case forward until the narrow ring at the base of the 257RA chamber makes contact.
That narrow ring makes a cut into the brass before it stops the brass forward movement.
The brass goes too far forward.
When the powder goes off the case expands and sticks to the chamber wall.
The back of the case is pushed back by the pressure.
This lengthens the case beyond elastic deformation into plastic deformation [it is not going to return to previous shape].
The brass was so deformed, it cracked.
I learned that if I put 10 gr pistol power in the case and covered with cream of wheat, there would be enough 40 degree shoulder formed on the next firing of that brass... to stand up to the firing pin push.
I warned the other guys. They headspaced 0.004" tighter and never had a problem.
In 2018 I chambered a couple 280 Ackley rifles. I used a PTG go gauge to headspace. Many deer died, but no cases failed...the Nosler brass was already formed:)