Jayson Cotter sells and installs the press on Flash Hiders for the PTR91. If it was my rifle I would skip the press on and for a little more have him thread it 5/8X24tpi. This is the standard thread for .308/7.62 and will let you install a bunch of different aftermarket .308/7.62 brakes, flash hiders, and sound suppressors if it is legal in your state.No it is not threaded and I had read somewhere that a press on type is available but haven't had the time to search. Thanks, John.
I am pretty sure his is just a crowned barrel with out any muzzle attachments.I purchased a flash hider from Jayson Cotter the website is www.investmentgradefirearms.com . My PTR had the muzzle brake also, but the barrel was threaded. When was yours made, it may have the threaded barrel? If not it would probably be worth getting it threaded so you have more options.