Possible muzzle threads on .574 barrel?

Got a couple rifles I wanna thread and get suppressors for, one is a 308 and tip of muzzle measured 0.574 inch, another is a 6.5 grendel tip is about same width.
Just wondering what are the possible muzzle threads to add to them?1/2 20 or 1/2 28 should be able to work right? Are they thick enough for 9/16 too?
Basically wanna purchase the right (cheap) suppressors then make sure the thread can actually accommodate, cheers.

1/2"x28 TPI would be good and still leave a decent shoulder for the suppressor to contact. 9/16" and 14mm will both leave a shoulder that is too narrow to get a positive register.

What Gundoc said.