“Rifle A” is a BCM 9” 300BLK factory Upper on a BCM factory lower with A5H3 buffer. Muzzle device is a Surefire Warcomp (open tines), and suppressor is a Surefire 300SPS. At 40 meters it is shooting 6-12” vertically strung groups while suppressed. Unsuppressed it groups fine. I shoot Barnes 110gr Tac-TX factory ammo.
Round Count: 62.

“Rifle B” is an exact clone of “Rifle A” complete with its own suppressor (the suppressors serial numbers are sequential). “Rifle B” has always grouped well both suppressed and unsuppressed.
Round Count: 28

To hopefully keep matters clear we will say “Can 1” lives on “Rifle A” and “Can 2” lives on “Rifle B”


Day 1:
Vertical stringing occurred on “Rifle A” with “Can 1” shooting suppressed at 40M. Group size was large (couldn’t measure as half the shots were off the paper of a smaller sized target). I assumed the optic was at fault and checked rings and fit and even tried it on a different rifle. Optic grouped fine and was not the culprit.

Day 2:
Vertical stringing occurred on “Rifle A” with “Can 1” shooting suppressed at 40M. Group size was roughly 12”. I then removed the can and shot unsuppressed. Group size was roughly 1”. I suspected the suppressor might not be concentric to the bore but could not visually determine anything wrong or off.

M4C- 2018-10-05.jpg

I decided to test swapping suppressors between rifles.

Day 3:
Vertical stringing occurred on “Rifle A” with “Can 2” shooting suppressed at 40M. Group size was roughly 6”.

Vertical stringing DIDN'T occur on “Rifle B” with “Can 1” shooting suppressed at 40M. Group size was roughly 1.5”.

M4C- 2018-10-13.jpg

This tells me the suppressors aren’t to blame. This leads me to think that there is an issue with the muzzle device, which I self-installed without a torque wrench. I installed the Warcomps on both “Rifle A” and “Rifle B” on the same day, back to back. Rocksett was used. I didn’t muscle them super tight, just firm enough to time them correctly, but I leave the possibility open that it may be torqued over the specified 20-30 ft lbs. If both rifles had this type of stringing I would be more inclined to believe it was due to over torquing. I could be wrong though.

What should my next course of action be? I’m nervous about potential baffle strikes so before I experiment further I’m going to inquire with Surefire but thought I’d pose the question here too.

Break loose the Warcomp and re install to spec? (I assume I would need new shims?) This would be hoping I didn’t mess up the threads/shoulder/bore if I did indeed over torque.

Check concentricity of barrel to threads? This doesn’t sound like something one can easily do at home. Can a good gunsmith? I admittedly know very little about this topic. Any thoughts are appreciated.