Can a muzzle device change POI? ...by a lot?

[themonk]

This is a factory BCM 11.5" LW Upper w/ 10" KMR that shot 100% to expectations out to 200 yards. 3MOA or so with a T1 at 200 yards right on target.

The only thing that was done to this rifle between it shooting fine at 200 and off paper at 100 (and about 5-6 MOA groups) was installing a BC 51.0 to ~30ft lbs. This was using the same ammo. I originally wondered if I might have used too much torque, thus distorting the crown/rifling at the muzzle, but after removing the muzzle device there was no way it was overtorqued.

The gas block isn't hitting the rail, I am not getting baffle strikes, I didn't use a crush washer, everything was done right. It's literally just the BC 51.0 on the end of the muzzle as a variable but I am really struggling to believe a muzzle device can change the POI by 15 MOA. Additionally, suppressed, my groups go from POA to 4 MOA at 8:00 which I've never seen this suppressor do on any other rifle (usually 2 MOA max, and always to 6:00)

It has since been re-installed to verified 25 ft lbs (well within AAC's 20-30ft lb spec). I'll try to take it back out this week and see if I can pinpoint what's really going on, but I wanted to ask here and see if anyone had any experience with an issue like this.

We can take the can out of the equation as the massive shift is just with the 51.0. Did you happen to shoot it after you took it off the first time? If so did the barrel go back to your original zero?

I have had shifts but never like anything you are talking about. I have a 51.0 but its in the safe waiting on a new upper so I'm not much help there. You may want to pop over to the 51.0 thread that I know you were in and see if anyone else had an issue like you're having with their install.

I would also send battlecomp an email and see what they say.

[Eurodriver]

No, I took it off about 5 minutes before I posted in this thread that I took it off.

I completely reinstalled the BC today. Using flat washers from AAC, got it to right where I wanted it while hand tight. I thoroughly degreased the threads (scrubbed with a brass brush, then degreased to make sure all of the old rocksett was off) then applied a bit of rocksett and using a torque wrench torqued it to 25 ft-lbs.

I'm taking it back out on Wednesday to 50 and 100 yards. I'll see what happens...

This is 25 ft lbs right? I'm not losing my mind?

Out of sheer curiosity - let's suppose I torqued it down the first time to 50 ft lbs, or something excessive like that. Will that cause permanent barrel damage or only cause accuracy issues while torqued? i.e. once the muzzle device is removed will it rebound back to normal?

[LRRPF52]

With high torque on the muzzle threads, I have seen deformed thread peaks, worse than the pics above. This is usually on badly-machined threads, or when someone is trying to clock an A2 flash hider without the right washers.