I like to start out 16" barrels with carbine length gas systems with an H buffer and a Tubbs flat wire spring and time from there. It's a pretty standard set up and the majority of the gas ports are within range to time correctly with this set up. Carbine length gas systems can be really rough on brass, but shouldn't be ripping the rims during normal operations. The heavy spring (questionable if you had to cut it down to get it to run with a carbine gas system) and H buffer shouldn't cause the issues you are describing. Too little weight or spring or possibly a bolt/barrel not headspace, too loose, could cause these issues. Who made the barrel? HBAR, Colt? Chrome lined? Was the barrel and bolt every headspaced? Where is it ejecting the brass, 2, 3, 4 o'clock? Pics of the brass and video of ejection would be good info.