I own 2 OTB cans and 4 regular cans. The OTB's sounded like a good idea, but after using them, they really don't offer much, other than saving an inch or 2 on overall length. I went to swap them amongst different guns and its a PITA. My OG hits the hand guard on my AR-10. My OG 6.5 hits the front sight on 1 Ar and the gas block on another. They don't fit on my carbon barrels. I now have a place where potentially debris can get in and be stuck while hunting. On my .223's, I am using a thread adapter and had to buy the special removal tool to get the damn adapter off from inside. (Worked very nicely.) With companies making 3d printed cans now that are short, light and as good or better suppression, I am not really seeing the advantages of otb, when looking for a lightweight suppressor.
If you are trying to achieve maximum suppression and not have a 10" can protruding past the end of your barrel, I can see some merit behind the ability to add reflex. I will admit tho, that I do like the look of otb on shorter barrels. I am thinking that going forward, my otb cans are really going to be gun specific. Set it and forget it. I thought the juice would be worth the squeeze, but in my case, I really don't think it is. This is my objective observations after using and comparing my cans. Your mileage may vary.
