Suppressor POI shift

O

oubeta

Sergeant
Full Member
Minuteman
Nov 2, 2003
535
6
Edmond, Oklahoma
#1
Finally got my REPR dialed in today.
Shooting pretty good groups at 100yrds.
I put my AAC suppressor (thread on) and it shifts the POI up so high I'm not even on paper. It brings it up almost 2.5' at 100yrds.
I can't figure it out. No baffle strikes and everything runs normal.
ALl my 556 suppressors have only a tiny shift in POI, usually no more than a 1/2" or so. Any ideas what could be happening?
I'm stumped.
 
#3
Re: Suppressor POI shift

I've seen POI shifts in the "inches" before, not really a problem so long as it is consistent shift.

I recommend you shoot some unsuppressed groups, then shoot some suppressed: does the rifle always return to expected POI and do groups stay tight with and without? If so (which is generally what I see): no problem, make a note and carry on.
 
#4
Re: Suppressor POI shift

It is not at all uncommon for a suppressor to cause a shift in POI (various reasons, including but not limited to a change in MV from unsuppressed to suppressed shooting, change in barrel harmonics by adding 1lb+ in muzzle weight, etc.).

Like Rancid said...shoot groups with the rifle suppressed and unsuppressed, record your POI's with both, ensure that you are getting a repeatable POI shift (which you should), and keep a record of it in your log book or wherever you keep your dope for the rifle so that you can dial up/down or left/right when switching between suppressed/unsuppressed fire.
 
#6
Re: Suppressor POI shift

On my 14.5" WOA, CLE contoured/fluted from a Wilson "match" blank, tested with three different BiLoc mounts, I get the same 3.5+ MOA shift down and 1.75" MOA right using my SpecWar2 SWR suppressor.
This fairly radical shift is unique to this barrel, which shoots very good groups with 55 through 77gr ammo. It does have a strong preference for heavier weights, and it is a 1/7 twist.
I have 1/7 twist 16" SS, 14.5" (MRP) CL & two 10.5" LMT CL (1 MRP) , as well as an 11.5" Bushmaster CL (also 1/7) that have near zero to 1+ MOA shift with the SpecWar.
 
#8
Re: Suppressor POI shift

I have used only about a dozen suppressors, but all have shifted down and some down and right. Never seen one go up or left. Not sure why. All of mine have consistant, Q/D or thread on.
 
#9
Re: Suppressor POI shift

mIne are going FEET high.
I switch the gas setting to 'S' and I can't even get it on paper, much less the target.
It's flying bullets way over the 100 yard berm and impacting on the 250 yard berm.
My spotter was calling the shots just low on the 250 but I was shooting at the 100 yard.
Tried it again yesterday with M118's and it flung them way high again.
Pull the suppressor off and back to 1-2" groups at 100.
I'm stumped. Suppressor is a AAC thread on.
 
#10
Re: Suppressor POI shift

Something is way off there. The good news is that anything that bad can likely be found and fixed. AAC makes a good can and I am suspicious of the threading job, but cannot understand how it could be that far off and not get baffle strikes. Are your action screws tight? Is the rifle bedded properly? ???
Have you bore sighted with can on and off? Good luck.
 
#11
Re: Suppressor POI shift

Oh damn! I just re-read your original post and realized that I originally mistook it to read 2.5 inches in POI shift, NOT 2.5ft!!!! That is definitely FUBAR!

Have you inspected your can? Any signs of baffle strikes or damage to the end of the can? Something has GOT to be wrong with either the can itself or your barrel threading is off (but still...you should be getting baffle strikes for a 2.5ft POI shift at 100yds).

I'd get with AAC and see what they say or what they can do for you. They'll likely want to see both the rifle and can if you have to send it for inspection/repair.

Do you by chance have another rifle you can try the can on to determine if you get the same, wild POI shift?
 
#12
Re: Suppressor POI shift

Guys I'm clueless.
NO baffle strikes. Believe me I checked several times.
Threads look great
It's on a LWRC REPR 18".

The gun shoots M118 175 OK, but put the can on it and it's almost dangerous to shoot. I even put some sub sonics through it and it was still way high over the 100 yard berm. Do you think this is a can problem or a rifle issue?
Can the gas setting make that much of a difference?
 
#16
Re: Suppressor POI shift

OK the error may be on my part.
Sometimes I leave the flat washer on that goes between the FH and the barrel.
I don't know why this would make a difference, but AAC says it would make a HUGE difference in POI. I'm headed back to the range today to see if it I left the washer on by accident.
Will advise
 
#17
Re: Suppressor POI shift

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: oubeta</div><div class="ubbcode-body">OK the error may be on my part.
Sometimes I leave the flat washer on that goes between the FH and the barrel.
I don't know why this would make a difference, but AAC says it would make a HUGE difference in POI.</div></div>

Huh...that is interesting. It makes sense to remove the washer and thread the can on without anything to interfere with contact between the can and barrel, but I can't imagine it makes a 2.5ft POI difference at 100yds. I will be interested to see how this one turns out.
 
#18
Re: Suppressor POI shift

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: oubeta</div><div class="ubbcode-body">OK the error may be on my part.
Sometimes I leave the flat washer on that goes between the FH and the barrel.
I don't know why this would make a difference, but AAC says it would make a HUGE difference in POI. I'm headed back to the range today to see if it I left the washer on by accident.
Will advise </div></div>


I have never herd of a zero changing that much unless the bullet is making contact with a baffle/s. Shake it out over a piece of notebook paper and look for jacket material. In theory if a spacer is parallel it should not make a difference but something is out of alignment on your set up.
 
#19
Re: Suppressor POI shift

Ya I don't see how that flat washer would make a bit of difference.
I leave it on with all my 556 cans and POI shift is tiny.
AAC says it makes a huge difference.
I shoot the suppressor. No jacket material. Baffle holes are all nice and round all the way through.
 
#21
Re: Suppressor POI shift

I read the initial post as 2.5 "inches", not 2.5"feet", definitely stop using the can!

Baffle strikes can be quite subtle, not alw3ays as dramatic as the can launching down-range.


Sounds like a light baffle strike.
 
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