One data point on port in the groove.
I have chambered AR15 barrels, never intentionally timed the port in the lands
This one came about by accident. It was melonited l, has 10,741 round count. I literally had to coerce by buddy that we swap the barrel before headed out to Perry. He was reluctant because the last 600 he shot was 198. The 8 came on #20. Jitters with the thought of cleaning the target. Mind you the shooter was 2 years into being a grand senior at that time.

I have chambered AR15 barrels, never intentionally timed the port in the lands
This one came about by accident. It was melonited l, has 10,741 round count. I literally had to coerce by buddy that we swap the barrel before headed out to Perry. He was reluctant because the last 600 he shot was 198. The 8 came on #20. Jitters with the thought of cleaning the target. Mind you the shooter was 2 years into being a grand senior at that time.
