wow seem everyboday like TBAC, what about silencerco, griffon armament etc? is there reason to choose TBAC over those company?
Folks here have been using TBAC for years, me included. The Ultra is simply one of, if not THE best, TI cans available. The Ultra 9 is the quietest, Ultra 7 is good all around and the 5" works better than you'd think and is super short and light. If length isn't huge, I'd go with the 9" You can always get the 5" later like I did if you want short. They can handle 5 mags of .300BLK for instance but then it needs to cool. Not sure how many 7.62 or 5.56 it can handle before needing a cool down but you can always ask. They use thread over brakes and flash hiders for mounts, which keeps 'em accurate, repeatable and is also convenient. Those little brakes really work, don't have their flash hiders but I bet they're fine. TBAC has probably the best CS in the business and they're on here all the time. They take care of you.
All of the following can be used for full auto. Sico makes good ones, the Saker is great, one of the better QD cans available and it's built like a tank which makes it heavy. Saker is probably the most adaptable can out there, has lots of mounting options (Trifecta is best IMO) and lots of different front end caps. The KAC QDC is really nice but costly, one of the best all around. Elite Iron makes great cans out of SS that thread over like the TBAC cans; being SS they cost less. They also do some amazing custom work. Surefire makes nice cans but they're generally considered to be more expensive with less performance compared to others. But they are nice.
I also have some AAC cans, couple of SDN6's and couple of 556SD's. I got the SD's cheap, one of the SDN6's on sale and the other full price. They're good cans, they're made well and they work but the mounts and CS is probably the worst in the business. I'd stay away unless you're getting it cheap. The only way to get a good mount without modifying them is to buy several (so shell out $500-$1000) and choose the one(s) that work, that you wanna keep, and send the rest back. Saker is most similar to an AAC QD can but without any of the problems.
Suppressors are the epitomy of compromise. If you go lighter you give up full auto, if you go quieter it won't be super short. So on and so on. There is no "perfect" one for everything but some work well enough. Usually using a larger bore can on a 5.56 will make it sound deeper, throatier (which a lot of people like). A dedicated 5.56 can may be quieter but not always --Saker 7.62 is quieter than the 5.56 version, but it's also a bit longer and heavier. You have lots of good choices, but basically if you can resist not blowing through more than 150rds. as fast as you can, then TBAC is where it's at. Performance plus low weight.