Yeah if you're using a mount of some sort (flash hider, brake, etc) and your barrel has the diameter for it (about .660" or so), 9/16-24 is a better choice than 1/2-28 just because it leaves more wall thickness around the bore. Not all companies offer mounts in that size, suppressors on hunting rifles haven't been very popular or common until the last few years and the "tactical" stuff is generally either 1/2" or 5/8". But more companies are starting to offer 9/16" threaded devices as hunting rifle suppressors become more common, so if that works for you it's a good way to go.

Note - my earlier comment in this thread about shouldering on the muzzle was in reference to mounts like this, I've made them and have seen some commercial mounts but don't remember who made them (maybe ThunderBeast?). If you go that route, a .630" barrel can be threaded 5/8-24 and use a mount that shoulders on the muzzle. FYI some 9mm pistol booster pistons are made that way too, Liberty does them that way for example so a long thread with no shoulder can index on the muzzle.

However, back to the 9/16 threaded mount - the shoulder requirement is still important, so if you're talking about a .630" diameter barrel I think that's a bit small for suppressor mounting. (That's enough shoulder at 9/16" for a brake, I've done that a few times, but a suppressor mount gets loaded more in bending & vibration and ~.035" shoulder is pretty marginal IMO.) I definitely would not go with a shoulder that small for a direct thread mount (repeated installation is hard on a small shoulder); it's arguable whether you can get away with it using a mount that's loctited in place but it's definitely pushing the limits. If you go ahead with that, I'd suggest very tight tolerance barrel threads that are cut to match the muzzle device.

If you have the option when the barrel gets threaded, adding a shoulder as gtscotty's pics show above is smart. It can be smaller and less obtrusive than those pics, but regardless it's a fairly easy thing for most decent gunsmiths to do. As long as it's locked in place well (loctite, solder, epoxy, etc) and then trued up it's a solid way to go.

About that 9/16-5/8" adapter - the minor diameter (meaning bottom of the threads) for 5/8-24 is .574", while the major diameter of 9/16"-24 is .563". That only leaves about .005-.006" solid material between the two threads so the adapter is not very strong. I had one fail when it was tightened down; it unwound like a spring and caused some minor damage to the suppressor threads, so it's not worth taking a chance on IMO.

Hope that helps.

Last edited by Yondering; 11/04/19.