Hello All Large zero change between suppressor installed and removed, I have a AR pistol, Aero Precision upper in .300 Black Out, 8 1/2 inch barrel, not sure of twist, believe 1:8. Flash suppressor is Dead Air quick attach and suppressor is Dead Air Sandman .30 caliber. Zero at 25 yards ( as this will be home defense weapon ) with no suppressor. Ammo is Remington 220 gr subsonic open tip Throw on suppressor and consistently pulling left 4 to 5 inch and 2 to 3 inch low. Shot groups remain good, perhaps a bit open with suppressor. Is this to be expected? I guess I can re-zero with suppressor on since that would be the normal usage. Also I did put that same suppressor on my LWRC Repr AR10 and noted groups all over the place. ( maybe ammo issue... this AR10 seems to prefer 168gr and i was using 147 gr 7.62.) or simply difference was shooting 100yds AR10 vs 25 yds AR15. I did not put time/money into resolving that yet.