You mean Case length not Over All length (OAL)
SAAMI specs are .960 max. Trim to .950
Shrinkage is the norm in a correct chamber with short fat straight wall cases.
It' hard to say where the marks on the cases are coming from with out looking at them.
Any bulges (Glock Smiles) just in front on the groove? Caused by less support at the mouth of the chamber.
Is the primer indention round or slightly oblong? Causes by cases coming out of battery too soon.
