Bro. Fudd. This is a helpful thread regarding measuring wall thickness
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=615160

Vol423 - you have confirmed that the chambers are still 2 1/2"? If so, I am in agreement regarding the safety of those numbers. I would not however use even low pressure 2 3/4" shells.