I tried to be as gentle as possible and this is the best I could come up with. Sorry, I apologize before you go further.
It fires a handgun cartridge and out of a 16" barrel flash will be close to nonexistent if not completely nonexistent so why add weight to the end of the barrel? I'd either leave the thread protector on it or get a longer one to protect the bore and be done with it. The flash hider is cosmetic? Yeah, OK, but anyone who knows what they're looking at will.... don't be that guy that they'll see with useless crap on their PCC that just makes it harder to use. Be the guy who has a PCC that has what it needs and nothing it doesn't. A flash hider on a sub2k is useless, adds weight and length where you don't want it, and will peg you as being "that guy". Now if it fired a bottleneck cartridge a flash hider could be of value but not for a handgun cartridge.
I could help you with checking the ID for the 9mm but I'll leave that to others.
If you end up wanting to hang something on the end of your (9mm?) barrel, then put a Kaw Valley linear compensator on it. You don't need a flash hider, as was mentioned by BJK, but at least you would get the benefit of directing the noise away from you and shooters on either side of you at a range.
I would just leave the thread protector on and call it good. That way, you have more options of carrying it in a smaller bag by not adding to the OAL of your carbine. Just my $0.02 worth.
Thanks guy’s for your replies. The reason I asked the question is because I intend on using my sub 2k for a home defense weapon.my thinking was directing flash and noise away if I ever had to use it indoors. Just a thought, I have the extra can and thought I might put it to use. Your points are very good and I appreciate your feedback.
Blast would be what I'd be most concerned about. You're not going to go deaf, nor will anyone else with even 30 rounds of 9mm fired indoors from noise. But if it was a bottleneck cartridge the blast will make you wish you'd never touched it off and it would be the ears that would be telling you that. But of course the sub2k fires a straight wall cartridge and not a bottleneck cartridge so the problem really doesn't exist.
FWIW, a flash hider wouldn't do what you state you want anyway. The linear comp or a blast forwarder maybe it'll redirect it. Now a silencer, aka, suppressor, can, muffler, would be the best flash hider available and also removes blast and the noise of a subsonic load. But unless the bullet is subsonic there will still be the supersonic crack that no can is able to get rid of. That means you'd still have considerable noise.
What do I do for my HD bottleneck cartridges? When I had a 5.56 as my HD carbine I put a can on it to remove the blast and it's noise and I was going to live with the supersonic crack. Now I have a 300BLK with a supersonic load as my HD handgun and it wears a can specifically designed to eat the blast but doesn't make the sound level ear safe (Amtac .30 CQB). Why is this? It trades sound, yet handles the blast, to give a short OA length, but blast is the killer indoors. A bit of noise isn't an issue. But again, it's not the few rounds I'll fire for HD that will damage my ears much. It's the decades before ear pro' that has done the lions share of the damage.
If you've attended many rock concerts the odds are that you've also damaged your ears from the prolonged continuous high sound levels. Those are among the worst type.
I suggest to folks wanting a rifle for HD, and if they live in a state that doesn't allow silencers, to get a 16" barreled carbine to cut the flash and noise, and of course there is no blast to mention. Why? Boyles Law states that when the volume s doubled the pressure is halved. So take the pistol cartridge and assume the powder is all consumed in 3" of barrel. That's pretty close. The 9mm operates at 36,000 psi thereabouts. At 6" the pressure is 18k, 12" it's 9k, and when the barrel comes uncorked the pressure is even less than that. Low pressure means less noise and blast.
So let's bring that to the real world. In competition my load actually used a powder that burned in less than 3" of barrel. My PCC (pistol caliber carbine) is actually a 7" barreled SBR (short barreled rifle) and other competitors have told me that my shots sound like a .22. We had an unsanctioned match where anything was legal and I put a can on the end of the SBR and used a subsonic 147gr bullet load with fast powder (I load my own) and while I couldn't hear it because my cheek was "glued" to the receiver so I was getting bone conduction noise and my ears were near the breech, the spectators could be heard commenting on the quietness of the combination. The range officer told me in an email that it was crazy quiet. But even w/o the can in place it would have been quiet as compared to a load that didn't use Boyles Law to the fullest. What that means for you is that the 16" barrel doesn't really need anything on the end. You can compare different loads to get what you want. Most (all?) standard pressure 9mm loads (not +P or +P+) using a 147gr bullet should be subsonic and that means no sonic crack. Lighter bullets should have sonic crack. You won't know what they use for powder in the loads, but someone standing at a distance should hear differences. I don't remember who makes them, but it's a major manufacturer that makes cartridges marked "for short barrels". I'd start there for the quiet loads. I'd test with and without the blast forwarder to see if it makes a difference worth having on the end of the barrel.
Good luck and please let us know how you make out. It might help others.