What is the barrel brand, length, diameter at gas block, chambering, etc? This info might help to get your answer regarding muzzle thread size.
Also, you might consider checking with the seller.
Edited to add: Most AA Grendel barrels have 9/16-24 RH threads, but I think some heavy barrels might be threaded 3/4-? RH. Other brands chambered for 6.5 variants are usually threaded differently (such as 5/8-24).
Also, you might consider checking with the seller.
Edited to add: Most AA Grendel barrels have 9/16-24 RH threads, but I think some heavy barrels might be threaded 3/4-? RH. Other brands chambered for 6.5 variants are usually threaded differently (such as 5/8-24).
Drifter