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Suppressors Point of impact change with suppressor use question.

Tazaroo

Private
Full Member
Minuteman
Nov 1, 2004
63
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Franklin, Wisconsin
So I went shooting with my new suppressor for the first time a few days ago. Suppressor is a AAC 762 SDN 6 and the rifle she was mounted on is a LMT M4 w/ 14.5" barrel 1/7" twist. I was amazed at the almost 5" shift in the point of impact on paper once the suppressor was on the rifle. I switched off between 40 rds of 68gr Sierra JHPBT and Sierra 77gr JHPBT and both impacted (at 100 yards) 5" low about 7 o'clock. Wind was at my back as well. With the suppressor off I was getting them all in the 9/10 ring with aid of my EoTech 553. Could the weight of the suppressor effect the point of impact that much? The lockup of the suppressor is pretty tight but with wiggle of about 1mm. Any thoughts?
 
Barrel flex. Does the same for me. Although, because you change the harmonics of a barrel anytime you change effective length and weight that much, the POI change could really go anywhere. Just note it in the log and make the adjustment.

ETA: I'm not familiar with that mounting system, but I would strive for zero wiggle. If you're having trouble with that, contact AAC and pick their brains. You should have no wiggle.
 
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The POS on my DD 16" Pencil Barrel AR15 , with a 5.56 AWC Raider,, Very similar to yours.
The POS on my 308 Bolt Gun, 24" Bartlien with a 7.62 Gemtech , almost none.
Wiggle will result in Baffle Strikes. Not Good.
 
Wiggle with AAC suppressers is an unfortunate fact of their mount design. They claim it is harmless and will go away once Carbon build-up accumulates.

But, there is a quicker fix - search the forums or google "aac mount" for lots of info. Basically you remove the finish on the mating surface of the mount --NOT the can itself. You will not be removing metal, or if so just a very light touch. People have done it with a dremel tool, sandpaper, or the best way -- in a lathe. (Just lathe the mount of course and not the whole barrel).
 
The only shift should be do to barrel droop, if you have a windage change the barrels ctr line does not line up w/ the cans baffles or mono-cores ctr line. All my cans are rated for F/A and are large and heavy. With the can on the .308 I have to add 2.5IPHY (22" 5.5 taper) of up only no windage shift at all. The .223 11.5" A-2 is the same except, but only needs 1IPHY of up, no windage w/ this one either.
If at all possible have the barrel threaded by the can maker, or have the can in hand before threading the barrel,... and always range off the bore, never the outside of the barrel like some do.