Air barriers with suppressed 300?

[Rancid Coolaid]

I've shot a few groups that look like this now, and it is an unusual thing.

I talked with a guy who has more suppressor (and subsonic) experience than me and he said it looks like an air barrier issue with a slanted baffle can.

Anyone else seen this?

Rounds were not rapid fired but were shot with short interval between. Nothing went super-, all were hand loads, should have been right around 1025FPS. All loads made at the same time, same components.

It was a windy day. The rifle has shot very nice groups, but there was more time between rounds that day (barrel break-in.)

Next trip to the range will be to shoot groups without can, shoot groups with can with chrono, and shoot groups with can and with Cor Bon factory subsonic.

Any help or insight would be greatly appreciated.


The rifle

[Rikky Lee]

Do as described. In particular, shoot without the can as you describe and tell us what happens. A factor to bear in mind is also the change in barrel harmonics with the heavy weight on the end.

Air barrier issue is a new one for me though.

[Spook]

I am dumb, what is an air barrier

[Rancid Coolaid]

Air barrier is a pressure differential due to the baffle design. I've been told slanted baffles can cause air barriers and can show stringing in groups like this.

Then again, it could just be high winds.

More to come when I get to the range and do some test shooting.

[Alleycat]

Air barrier = barrel touching the stock due to the extra weight of the suppressor and insufficient clearance.

[Rikky Lee]

Also try with the silencer on at 50 yards and compare group sizes.

I'm thinking a weight issue still tho'.

[PFDD]

You know I saw the vertical stringing and I wonder if Alleycat isn't on to something?

I had a Husqvarna rifle that would exhibit the same groupings until I identified that the stock inletting was insufficient on the forend and it was binding and reseating with each shot. There was no suppressor involved just a hunting rig in 7MM Mag but after restocking in a McMillan stock all the stringing issues disappeared. I could have cleaned up the forend on the old wood stock but wanted to switch it out anyway so it was a good excuse.

I wasn't aware of a theoretical air barrier issue but my cans are all traditional stack baffles. You may want to double check on the stock clearance as Alleycat suggests.

[Rancid Coolaid]

Alleycat, the definition was provided to me, it could be off.


I hope to have the rifle on the range tomorrow or day after for some evaluation -sub and supersonic.


The barrel channel seems to be adequate to keep the barrel off the fore end.


More to come.

[amafrank]

As a simple test you can take some very true shims to change the orientation of the suppressor on the barrel. Try a number of different locations by changing the thickness of the spacers. Put a line on the top when you start and try at least 90, 180, and 270 degrees from there. If the baffles are truly the problem you will find that the stringing changes each time but remains a measureable issue. If its just a weight or ammo issue than it will change but not necessarily in the same order or arrangement. Suppressors normally change the point of impact in relation to the point of aim unsuppressed. I have heard people say that the baffles and jets in the can will create issues with accuracy but I've not seen but very few cases where that seemed to be the real cause.

Good luck and keep us posted as you find things.

Frank

[Rikky Lee]

The other advice is to put a piece of tape over the suppressor. See if the bullet is leaving dead center. If not shim the mount 180º from the area where the bullet is off center. Then see if the tumbling continues.