Thread: Brass length trimming question

Originally Posted by robh500

I recently brought some peterson 280ai brass, it was all very uniform and all measured at 2.5190 or there abouts before firing.
I just deprimed and amp annealed and then sized with a Redding full length die and checked lengths, some were as long as 2.5520 is having to trim .75mm normal?

Unfortunately I didn’t measure any after they had been fired before I sized them. I thought maybe the die could have been stretching them with the button on the up stroke? Especially after being annealed and a bit softer?

I will measure some before and after firing next time.

Only some are long, maybe 75% need trimming, maybe 20% need up to 30 thou taking off.

Just wanting to know if I’m worried about nothing!
Cheers

Greetings Robh500,
Contrary to popular belief it is the full length sizing itself that makes the cases longer, not the expander button. Setting the full length sizer die to just size the case enough to chamber with slight resistance will reduce the stretching. The new cases are always a looser fit in the chamber as they have to chamber in all rifles. It is also harder to make cases as uniform with the 40 degree shoulder on the AI. By all means lubricate the inside of the neck, as I do, but this will not stop the stretching if the case is being over sized in the FL die. The above steps should reduce stretching to a minimum as will neck sizing in a bushing die.
Regards Grandpamac.