i dont have the mach2 shells yet,but im shooting the aguila shells right now till i find some mach2 bullets..ive got it zero'd at 50 yards and im getting half inch groups.same with 25 yards and 75 yards. i tried 5 shots at 120 yards and it is shooting 6 inches low with about 2 inch groups..im very pleased with this nef. and to the nosey guy, it is a rimfire so who cares if i post it here and not the nef marlin forum.