BA 12.5". 8+ moa with suppressor, 1 moa without suppressor

[VASCAR2]

Current Hornady 123 grain SST are not producing as good of accuracy as they did a few years ago. Most everyone on the forum get better accuracy with Hornady Black 123 grain ELD-M. Several forum members purchased AP/BA 12.5” 6.5 Grendel barrels and BA used a small gas port assuming most user would use a suppressor. I suspect the small port size attributed to your failures with no suppressor.

I’ve never run suppressors so I can’t help with ideas on any issues there.