4/5 sub moa, 1 flyer - Norma Whitetail 6.5mm Creedmoor 140gr Brass Cased Centerfire Rifle Ammunition

I tried these rounds in my custom M5, and it seemed like 4 out of 5 grouped within 2.0cm at 150m, but 1 out of 5 would land ~20cm off. At first I assumed it was me or from the barrel getting hot, but after 40 rounds it seems more like ~20% of the rounds were slightly off.