I'm confounded. I originally put my Vortex Viper PST 1-4x mounted on a ADM scout x qd mount, with a 18" black hole weaponry .223 wylde stainless barrel, SPR type build. I was getting cloverleafs at 50 yards with American Eagle 55 fmj. Now, I traded my friend for for my 15" Samson evolution handguards for his 15" MI SS handguards. Changing out the handguards necessitated a barrel nut change. Went this weekend to re-zero my rifle. Started to rezero my rifle and I couldn't get it to rezero. My shots were going all over the place. Literally. Now I don't think its the shooter (tho I'm not the greatest shot) I was getting 2 inch groups with my friends Savage bolt action .223 with a fixed 10x at 100 yards, using pmc 55gr fmj. I even helped him sight it in as for some reason it was about 6 inches high. I also had some fun with my other friends new Vortex Viper HD 5-20 EBRv2 on his 20" precision setup. Didn't shoot for groups with it but took it out to 500 yards and hit some steel plates with it. Very nice glass. Now my primary concern, is that I shot one mag of cheap russian steel case ammo, to test out my gas system. One shot stuck and I used a brass rod to eject get it out. I'm afraid I may have scratched the barrel. I can't conceivably understand why my shots were like all over the place. At 50 yards a damaged crown wouldn't make my groups like 4 to 5 inches off would it? I couldn't sight it in. After about 50 rounds, I called it a day. Decided to try it at a later date. Here's what i tried. I tried different ammo. PMC 55 gr fmj, PMC Xtac 55gr fmj. (didn't use the expensive stuff) I cleaned the barrel numerous times. I check the crown. I removed the muzzle device. I removed the scope, made sure the rings were on tight. I tightened up the qd lever. I tightened up the handguards (tho the scope is mounted on the upper receiver) I just kept bringing the POI down, then it would go left, then it would go right, but pretty big amounts. like 3" off at 50 yards. I need some suggestions to try out, what say you?