If you are at six minutes then floating will not help much. It does help if you tend to sling up hard but you should be able to see 2-3 minutes off a bench without a problem.

To see 6 inches I would start looking at my sights. If you have raised your front post to far it can wiggle. Is the sight base tight? If you have a detachable handle it might be loose as well. If scoped, how is the mount? Cheap scopes/reddots can move with recoil.

Are your holding the same? I have seen issues with red dot users with larg moa dots having a hard time with consistancy.

A 1/9 should shoot 50gr - 69gr without a problem. The Fed bulk 55 shoots 1.5 for me at 3300 ft/sec, the American Tac is about the same. Same rifle with 69gr SMK at 2700 ft/sec does .75 inch or so. The bulk stuff will have a flyer every now and then but should group well overall.