Suppressor companies often make some interesting claims about accuracy, such as suppressors not changing POI or tightening up groups. This can and does happen, but so does cause changes in POI and opening up of groups. The issue isn't just the suppressor.
With a properly mounted good suppressor, the change in group size or POI (or not) may not have so much to do with the suppressor, but the barrel harmonics change or droop by the addition of the can to it. Think about the differences in POI and group size between a properly rested rifle versus a rifle rested on its barrel, for example.
From what I have seen, heavy barrels tend to be influenced less by the addition of suppressors than lightweight pencil barrels.
Keep in mind that your most accurate ammo in your rifle unsuppressed may not your most accurate ammo suppressed. You may find that if your group opens up with your suppressor, that by changing ammo brand, model, or weight, your groups may tighten again.
You can go on Youtube and find several videos where folks test group size, POI changes, and repeatability of suppressors on particular rifles and with different ammunition. The bottom line is that the issue isn't just with the suppressor, but with the combination of the suppressor, rifle/barrel, and ammo.
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Direct thread suppressors tend to be more consistently stable regardless of brand because they are not apt to wobble. Quick detach suppressors can vary in their repeatability, though several companies have models that are rock solid.
Silencerco's Omega (works on a couple of models) system comes with both direct thread and QD parts and so you can go either way, but the QD is reliable and repeatable.
Surefire's SOCOM suppressors are solid QD mount systems as well.
I would avoid any of the AAC 51T QD system suppressors. The 51T mount has proven to be problematic for a lot of users.
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You didn't mention your caliber. If it is a magnum caliber, be sure the suppressor you buy is rated for it. Just because the suppressor has the right size hole doesn't mean it will handle the caliber.
Also, if your rifle caliber is smaller than .308/7.62 (such as .223) and you don't need the absolute most noise suppression, go ahead and get the 7.62 size suppressor as it will offer you versatility for using on other firearms. From the tests I have seen by Silencer Shop, the increase in noise by using the suppressor oversized hole is 3-5 db in most cases. - Just something to consider.