Never encountered this so posting here to see if other have had similar experiences.

Just had a rifle built:
Lone Peak Razor action
16” Hawk Hill 1-10 .308 barrel
Magpul PRO chassis
Surefire 762 RC 2 suppressor
Surefire SFMB muzzle device.

I’m at 60 rounds down the barrel and can’t get the rifle to group as I expect. Groups are consistently around 2”. I have tried FGMM 185gr, Hornady 178gr eldx factory loads, and M118LR.

I took the suppressor off and the rifle shot better but still not great (will put two rounds in the same hole and a flyer always, consistent between 2 different shooters). It’s apparent that the suppressor makes it worse, I will also note that the suppressor is brand new and all it has through it is what’s been put through the rifle. Screws and everything have been checked for tightness. Has anyone else run into a similar issue? Am I missing anything?

Pics of recoil lug channel after pulling the barrel:https://imgur.com/a/7ny1OCZ

Shoot it bare muzzled and see what it does.

Pesky harmonics.

I've occasionally runs into issues with a muzzle braked rifle just not grouping turns out any muzzle device torqued on was the culprit.

Sounds like harmonics to me.

I don't think the surefire cans are meant to be precision oriented, but that's pretty bad.

Try shimming the brake in/out a bit to "lengthen" or "shorten" the setup by a couple turns.

Especially if you have a big fat shim that wasn't used, throw that in there. You should have enough threads to spare.

Try and see if there are burrs in the can? Maybe a burr could cause something fucky with the way gas/shockwave get disrupted, and make it inconsistent.

I had really bad luck with the juggernauts and the 178 hornadys didn't do very good for me, but m118lr is around 1moa in my 308. Either way, the can shouldn't make it go crazy.

Did you check the bore Alignment with a ore Alignment rod? I had a gunsmith install my muzzle brake timing shims wrong causing a baffle strike I had to send my 6.8 socom back to sure fire and have my barrel cut down and re threaded. The sure fire muzzle brake comes with the spacer washer that is concave on one side and flat on the other the gunsmith installed it with the conncavr side against the shim and spacers crunching them up and making the muzzle break tilt

Negative this muzzle device was timed when the rifle was built so no shims.

Still though. Try it without the MD

UPDATE:
Pulled rifle from chassis and there was an abnormal amount of wear around the recoil lug on the action and in the recoil lug channel on the chassis. Thinking the lug is moving back and fourth in the channel while shooting. Bedding the channel to see if this fixes the issue. The recoil lug channel in this chassis is almost double the thickness of my recoil lug.

Also try some 168 GMM. None of the ammo you mentioned would be on my list of test ammo. 168/175 SMKs are a great benchmark as they aren't finicky about OAL or velocity.

They make different sized recoil lugs for remingtons. Did the guy who installed the barrel have the chassis in hand?

Chassis is being bedded then I will be trying some 168 FGMM. I purchased the chassis myself and the recoil lug is integral to this action.

Suppressed 100 yard group using a poor reputation stock Remington 700 SPS barrel...