FC brass was loaded, as fired, from a Ruger Mini-14 in 1996. No cleaning or liquids used on the brass, wiped with a large towel only. Total loaded about 250 rounds. Load was IMR 4198-20.5gr-Win 55gr fmjbt-Fed205 primer-Col 2.250"- RCBS Standard dies on a Dillor RL 450. Fired in a Savage axis. After firing, shoulder set back still measured .004" shorter then chamber. Ammo was gauged & compared because of previous problem with the Dillon Shell plate being under size at only 1 station. This pushed the shoulder back as much as .014" on some rounds. So these remaining rounds were checked for head to datum length. My guess is the brass is brittle from poor annealing?? Head stamp is the large lettered FC. Had this before, firing an M16A1 carbine, with LC & FC brass, soaked/washed in a vinegar, salt mix, old NRA formula. Thought is was dezincification at the time. Guess not?? After a closer inspection, all fired brass has a small split going clear thru the brass in the middle of the neck area. The loaded ammo is perfect, no splits.