After 17 1/2 months I received my tax stamp for gun trust and picked up Keystone Lake Armory 300 Blackout suppressed barrel. The upper had been recalled for modification to prevent removing suppressor which would result in a SBR therefore 2 stamp rifle. Shooting 125 gr reloads at 10yd ,I got 12 inch group with key holing and one perfect imprint of sideways bullet. I haven't been able to disassemble barrel.Thought about drilling out exit hole. Help!