A lot of people do; some pin/weld a can to an 11.5 or 12.5" barrel to bring a rifle to 16" so the can is permanently attached; others do it even if they don't have to because the can is dedicated to the rifle and there's zero need to quickly detach the can from the barrel, so why bother. It's got it's downsides though, including cleaning if you're never going to take the can off (if you lose a patch in the baffles, good luck). The main downside with a direct thread is every time you take it off and put it on, you may stretch the threads a bit especially if you over-torque it, and if you cross-thread it you now need to send your barrel off to be repaired, or if it can't be repaired, cut and re-threaded. That becomes a problem if it's a 16" barrel and you can't cut more without putting it in NFA territory...then you'll be forced to pin-weld a muzzle device anyway, or buy a new barrel. It would also suck if the threads aren't concentric with the bore, but that's a risk either way.
Of course, if you never take it off ever and just clean through it (Which is fine, plenty of people do), the can will probably be carbon-locked to the barrel after a thousand or two rounds anyway...may as well be welded
It would be, for sure, both the shortest and lightest, if you direct thread a can on. The direct thread adapters are lighter than the muzzle device + adapter to connect to the muzzle device...even if it's only a few ounces, it'll still be lighter.
With the can attached, the only difference between them would be that a muzzle brake can act as a sacrificial blast baffle and eat some of the wear that would normally go to the blast baffle in the can. Having said that, sometimes it can have detrimental effects on sound...see Pew Science's tests of Socom RC2s, both with the 3 prong flash hider, and the Warcomp brakes - with a Warcomp installed, the can was much louder to the ear; noticeably louder. On shorter barrels, shorter than 12", a brake is probably not a bad idea to eat some of the baffle wear - just be aware of the tradeoffs. Longer than that, a flash hider is fine IMO. Otherwise - they really have no difference when a can is mounted as far as whether it'll act as a muzzle brake or not...the can isolates everything.
How do you mean? The shorter the barrel, the faster the blast baffle erodes from all the crap and blast that hit it; there's a ton of threads on arfcom including a long running thread photoing blast baffles at round counts on long and short barrels. Cans that mounted to brakes fared far better than cans that didn't (SOCOM RC2s in particular with the 4 tine flash hider show some hideous erosion issues at higher counts). Every manufacturer that's participated in threads like that there has said that brakes work great as sacrificial first baffles...they're also a lot cheaper and easier to swap out when they get worn.
As far as barrel length goes, that's just a SWAG on my part. I wouldn't get concerned about baffle erosion on 16" barrels, but I'd start to get worried on 11.5", and definitely worried at 10.3 if I were going to shoot it a bunch, no matter how stout the can is claimed to be.
Well, define "fine"?
"Fine" as in "if/when you wear it out we'll replace it", or fine as in "it'll never erode, we're using diamond baffles and it's impervious to high pressure particulate matter"...I can virtually guarantee you it's the former and not the latter. Tons of cans still have barrel length restrictions, for this reason.
Just because they say it's "fine" doesn't mean it won't erode the baffle; it just means the manufacturer prepared to deal with it. If you're prepared to monitor the blast baffle and send it in when it's blatantly blown out, go for it, nothing's stopping you. I'd rather look at my muzzle device and when it's flame cut, blown out, or otherwise worn to the point where I think it's not doing it's job anymore, I'll just spend the $75-$100 on a new muzzle device and keep on trucking of a good cleaning can't restore it.
Ask them about 7" barrels, see if their tune changes...nothing escapes one of those without scars. I'd also bet that the 10" barrel being "fine" is contingent on it not being on a full-auto host...then again if you're buying for a gov't entity then it doesn't really matter; you can just get a new one when you blow out the old one.
I'm not sure why there's so much talking past people in this thread. @Robinson asks about cans and people starting talking to him like he's an idiot that thinks he can shoot without earpro when that's never what he said he wanted to do.
Similarly, I'm asking for data about your assertion on using flash hiders below a certain barrel length. I understand that brakes can act as a sacrificial blast baffle. I also understand the sky is blue. I'm not asking about either of those, however. I asked for data about your assertion that flash hiders shouldn't be used below a certain barrel length.
If you don't have the data to back up that assertion, then you don't have the data. That's it. That's fine. That's all.
"Are you ready? Okay. Let's roll."- Last words of Todd Beamer