I have a 308 that I shorted to 16" for a quick truck gun. I have been shooting it with my PTR VENT 1 on it to sight it in. I couldn't patter it at 50 yards for anything. Would even have some not even hit paper. I took the can off and shot a group of 3 over top of each other. Vent 1 is just direct thread. So what do I need to do?

Is it a thin profile barrel? Chances are your barrel harmonics are all outta whack! Especially if it shoots great without the can, but adding the can makes its groupings go to hell with that ammo.

Is this happening with subsonic loads or supersonic or both?

Is the suppressor walking off? Try with QD mount?

Leave the can at home.

I worked on my boss's .308 rifle for the same issue. Found out the bullets were tumbling out of the suppressor. Telltale sign is some of the bullet holes in your target paper will look elongated instead of looking nice and round like a hole punch.
If so the bullet is not stabilizing coming out of the suppressor.

Shooting supersonics. Have tried 3 or 4 different ammo's, same issue. Holes don't look like tumbling. and I don't think I am getting any baffle strikes unless it is at a micro level that can't be seen. Everything else I have shoots perfectly with that can.

Gun is a Ruger American

You either have a harmonics issue or the bullet isn't stabilized as it leaves the barrel and the gas disruption in the can is making it worse.

Try a different can or see if a muzzle device helps. After you verify that the can bore is on the same axis as the barrrel bore.

Yea the tumbling is notorious on some subsonic loads but rarely supersonic
Check the alignment with an alignment rod.
Baffle strikes can be very minute to not be seen easily. (If at all)
Shoulder could be crooked from poor machining.
Suppressor weight is causing barrel harmonic issues.

If Ruger American = factory threading

True. But they can still mess it up. Ask me how I know.

Oh not saying they can't just ruling out blaming some local machine shop guy

Don't worry everybody, I'm here to weigh in on this lovely topic!!!

99% chance it's either the can worked loose or it's mounted out of alignment causing baffle strikes.

Harmonics are a thing, but don't impact accuracy or bullet flight. Especially on a short 16" barrel. Even if node and harmonics were real it wouldn't account for missing paper completely at 50y.


He mentioned he got the barrel cut down, so they're not factory threads.

What ammo are you shooting and what is the battle twist rate?

With direct thread, make sure the can is making full contact with the shoulder of the barrel. If the threaded portion is too long, it can snug up internally and not against the shoulder. If this is the case, you need a machined spacer.

Roger that

This.

Thanks. Will check on those things asap.