I am pulling my hair out. I have a Noveske 300/221, 16.5 barrel, 1-8 twist and a AAC Cyclon supressor. While out at the range I ran some super sonic 165 Noler's through the gun with no problem. Then switched over to the HSM 220 sub sonic 300 rounds and fired 3. THe first one went 4 inches low and the last 2 were touching at the POI. Tried it again, loaded the 20 Bushmaster mag with 3 rounds and fired the group. Almost exactly the same outcome, 1 went 4 inches low and the other 2 at POI and touching....?????? so I switched over to my Sub sonic rounds. 220 HPBT Sierra with 13.5 of H335, COL at 2.26. Again the first round went about 5.5 and fired 5 more that were touching at POI.....????......the one thing that was noticeable was that my loads hit the paper unstable due to the impact print. As you would expect I went through the gun and mag's. Inspected the barrel, suppressor and mag. Everything looked fine. Suppressor was tight, no visible damage, the bores were clear nothing rattling. Disassembled the gun and re-assembled it. Ran 3 more HSM rnd's through it and the same damn thing.???? so changed mags, NO change. I am at a loss........the only thing that i can determine is that the 1st round is loaded into the chamber by charging the bolt and the rest of the rounds are loaded due to gas pressure....????? shouldnt make a difference but I am at a loss. Please anybody.....................I have been loaded for several years but I am by know means an expert. If you want I can supply pics of the target that i shot.