Anywhere there is fine sand. It isn't even about rounds fired its about dependability in multiple conditions, and overall life span. The piston system handles sand, water or mud. I am not arguing semantics. I am stating my experiences with the two systems. I own 4 DI guns and love them. One of the is the most accurate AR I have ever owned(24" barrel). But I won't deny the piston system is better, if Hk, or LWRC.
" The strongest reason for the people to retain the right to
keep and bear arms is, as a last resort, to protect
themselves against tyranny in Government...." - Thomas Jefferson