I saw the same thing on my M4-2K.  Moved it from my precision AR to my combat AR.  A group I did on my precision AR using the M4-2K with the can on, and the can off.

Just shot my buddy's m42k again yesterday and while it sounded great on a 14.5", he has admitted to marrying the can to the upper so he doesn't have to mess with the mount

Ive been happy with mine.

I think the mount thing is over blown.

I have and know others personally who have had a latch wear out.

Just hold it down when attaching and its a none issue.

Quietest 5.56mm can I have, but I only have two. This one and a Surefire Socom.

While I've never shot my M4-2000 for ultimate precision necessarily, I do keep a 51T SDN-6 on my 308 that is solely used for precision.

Ran said 308 through two different 3 day, 30 hour, 1000 yard precision courses with the SDN-6 mounted at all times. Class goal at every distance was MOA or better. Within 600 yards, I rarely had a problem delivering on that goal. Beyond 600, well, the wind definitely started to factor in much more, and overall, groups were surely opening up. Though that was more the cartridge and the elements than the can.

That's pretty wild.

I have 4 5.56 ARs with 51T cans on them. 3 with Mini 4s, and 1 with an M4-2000. I pretty much just shoot suppressed now, so I haven't tested accuracy with them on and off in a while. That said, a few years ago, when I still just had 2 51T cans, I did swap them around a bit, and got to check accuracy with and without the cans. Aside from the slight POI shift at 100, I never really noticed much of a difference in accuracy with the cans on and off.

Scary thing is that I tried 3 different mounts, and it didn't help.  I ultimately bought a TBAC 223P-2 to run on my precision AR, and it groups very tightly.  The M4-2000 itself is a good can, I just don't think much of the mounts from an accuracy point of view.  On my 16" and 10.5" combat AR's, it works great, and the accuracy on those AR's with the M4-2000 is acceptable (2 MOA with typical combat ammo).

Interesting.

And yeah, sounds about right. I have all those 5.56 51T cans on more "combat" setups. Usually running PMC Bronze, and they're all about 2 MOA capable with that combo.