Well, I've got two AAC 556SD's --similar to your M42000 but a bit simpler and shorter. I got two of 'em for less than $1000 and needed two for two blind pinned M4's I did right before we got SBR's here.
I have a pair of SDN6's too and found a better way to get mounts for AAC 51T's: what you do is order ten mounts (I prefer the brakes) and select the one or ones that fit and send the rest back. No grinding or work that kills the warranty. Sure you gotta buy $1000 in mounts, but you'll be sending all but one or two back. Also, the SDN6 makes a good hard use 5.56 can, it has a "throatier" or deeper signature that some prefer to higher pitch sound the 5.56 bore makes. Both are about the same regarding performance.
I finally got a Sico Saker in 5.56 with the Trifecta mount. Oh man! It's quieter and they've also come down in price since I got it, they were $1000 but now you can score one for less, especially on a sale. The AAC cans are made of Inconel and that's tough, but the Saker is made of Stellite and that's what they line M2HB barrels with! For any future 5.56 cans, I'll be getting these (when there's another killer sale anyway and I have the funds). They have to be good for me to buy more than one, that or good enough and on sale. With that can there's just no complaints. True QD, locks on tight with one hand, off with one hand, great performance and it has interchangeable muzzle caps. All sorts with even more available with the 7.62 version (which is also throatier AND quieter than the 5.56 can; also can be had with a 5.56 end cap). And it'll accept a plethora of mounts from other companies, so it's one of the more versatile cans out there. Trifecta mount is the best though, no ringing as all tines are different lengths. BE Meyers even makes a mount that'll fit!
Those cans are for abuse or hard use and they have a bit of weight to 'em. I call 'em "military cans". For other stuff, bolt guns, slow fire for the most part, not getting in firefights, the TBAC cans are great. But they can overheat if you fire too much without a cooldown. SBR's make this worse. I use a few TBAC cans, mostly on .300BLK SBR's and 6.5G's. The limitations for .300BLK are pretty generous, 6.5G doesn't get mag dumps and even some rapid fire is fine. But for hardcore use, mag dumps, full auto, etc., you want a hard use can. I haven't used or seen their take down steel can, I'm sure it's nice, it does look nice, but can't say anything about it other than TBAC doesn't make trash. I don't understand why it's takedown unless it's mean to be used with .22LR also. It's probably the only one, maybe one of a few, hard use rifle cans that can be taken down.
Another that doesn't get mentioned much but makes great cans with no gimmicks is Elite Iron. I have their .50 and .338LM cans. Their smaller cans are similar, just smaller. He claims he makes one of the best 6.5G cans and he doesn't boast or blow smoke up your ass. Not only are they accurate with repeatable vertical POI, they're 316SS and are hard use cans. 316 keeps prices down over exotics and the owner is a metallurgist by profession and claims exotics really aren't necessary. I do think he uses a different material for the blast baffle though. Very well made, solid. They have mounts similar to TBAC, thread over QD mounts. They have some other items available as well, like linear brake caps for their flash hider mounts, etc. They will index your mount or suppressor TDC so POI is vertical. They also make the brakes for McMillan rifles and the cans for DTA. They are a top notch business and the cans are good for high volume and precision.
I'd do my homework before a new can purchase, new things may be out, but I stick with known mfg.'s and generally go with cans that have a stellar record. So were I to get another 5.56 can today, it'd probably be another Saker. Unless it was a bolt gun, then I'd get a TBAC Ultra 9.
KAC makes the can for my SR25 and it's amazing, expensive but amazing; they really thought of it all and it may be the best all around 7.62 can made, but I don't know anything about their 5.56 cans. If I got a KAC upper though, I'd probably get one just because of their reputation and past experiences. I'm sure their full size new 5.56 can is amazing and I'd give it a look anyway. Especially if you talk yourself into a KAC upper. You can get a KAC lower from Small Arms Sales or Tombstone. Prices have gone up on these from 198 to 200 to 204 for stripped lowers, so I'd get some before they keep going up if you want a 100% KAC rifle. They always sell out at any price so far and they'll keep raising it until it reaches an equilibrium.
Lots of good choices but I'm not a fan of new mfg.'s or gimmicks, I keep it kinda simple. These are all cans I either have or have experience with. Suppression depends on a lot, where you fire it (echo, inside, close trees, etc.) ammo, other ambient conditions. I'd say the 556SD is the loudest 5.56 can but it's very short actually, almost a moderator length. The Saker is short but has great performance. It's the full size version, the 7.62 would have been quieter but a bit larger. TBAC Ti has it's limitations and don't know much about the their Takedown model. KAC can't go wrong but it's costly. Elite is a great mfg. for a killer price. Maybe the best all around when you factor price into it. Lots of alphabet soup agencies he can't talk about use Elite.
So good luck, hope that helps some!
