My money is on the barrel harmonics have been totally f#cked up by the machining and muzzle brake.
Why did you feel the need to get it in the first place?
Back to the drawing board buddy. Give that barrel a good clean, get all of that copper out, and start again.
You'll have to try developing a load that works with the new set-up.
Not having a go at you, just looking from a different angle. Good luck.