POI shift suppressed vs unsuppressed

rlbreakfield

Private
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Feb 23, 2017
57
1
12
Mississippi
#1
My POI shifts 6” high and 2” left when shooting unsuppressed vs suppressed. The rifle will shoot 3/4” all day with 175 FGMM suppressed.

My setup is thunder beast ultra 7 CB 30 cal. Remington 700 AAC/SD, .308, KRG X-ray chassis, Minox ZP5 3-15x50, FGMM 175.

Is this typical? If not how do I fix?

THX
 

Gtscotty

Private
Minuteman
Jul 22, 2018
74
79
24
#6
Seems like a big shift, I use my 14.7 oz Liberty Sovereign on a few different rifles and see the following shifts @ 100yds:

24" RPR 6.5 - 2.5" down
20" CTR .308 - 2" down, 0.5" left
18.5" X-Bolt .30-06 - 1" down

With my heavier Saker 762, I see about 1" more shift with the RPR and CTR. Both of the cans give repeatable shift though, so I don't really care. Is your shift repeatable?

This thread reminds me, I need to check the shift on my Kimber Montana this weekend, just in case I pull a stupid sometime during the season.
 

PFG

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Dec 13, 2017
178
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#7
18" CTR with a TBAC 7 Ultra is dead nuts left and right, and 2 inches lower.

I think the shift you're experiencing is worth more investigation.

Are you using TBAC's thread over break? Or direct threading onto the Remington barrel?

My first thought is to spend some time really looking over your method of mounting the TBAC to see if anything is amiss.
 

Zak Smith

TBAC Guy
Commercial Supporter
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Nov 7, 2003
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#8
6" is definitely more than we see in virtually high quality bolt guns that do not have some other problem. The most likely cause is barrel threads / shoulder that are not perfectly straight and square to the bore. This can easily cause enough runout on the suppressor that the bullet doesn't quite kiss the endcap, but gets close enough to be "blown off course" and this often screws up accuracy some too.

Next would be harmonics / bedding, or other rifle-system issue, that is exacerbated by the suppressor. Typically we see this in bolt guns where a lot more is happening dynamically during firing, but we also see it sometimes due to an incorrect bedding job or something causing a weird barrel harmonic. This can often but not always be debugged by replacing the suppressor with a rigidly mounted weight of the same mass to see if it's replicable without the suppressor on.

We'd be happy to examine any or all of your system. We accuracy-proof-test suppressors all the time and it basically always comes down to the mount (in our case the CB or BA brake) being on the barrel somehow wrong.

Give me a call tomorrow and we can figure out what to look at next
 

rlbreakfield

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Feb 23, 2017
57
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Mississippi
#9
Thx for the POI comparisons fellas.

If I could afford something better than the rem right now....I would have something better

The factory threads were definitely not concentric to the bore. I had Accurate Ordnance cut the barrel back one inch, rethread the barrel and time the CB break before I fired the setup. The CB brake has not been removed from the barrel since I got it back from AO. I’m 100% pleased with the can/brake I’m just looking for guidance on what I can do on the POI shift. Mr. Zak gave me some things to try to troubleshoot. Thank you Mr. Zak! I’m gonna try his recommendations and see if we can clean it up a little.
 

PFG

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Dec 13, 2017
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#11
@rlbreakfield good to hear it.

Don't sweat the poor threads from Remington. My Tikka CTR was crappy as well (missing the undercut between the threads and the shoulder). Similar to you - I had the barrel chopped and re-threaded to avoid any issues.

Keep us posted on what you find.
 

WALLC

Private
Hessian
Minuteman
Sep 28, 2018
11
1
12
#14
I had the opportunity of running the Q Full Nelson (Direct thread) with their Fix 6.5 22” and experienced little to no shift at all (at 100).

6” seems like a problem. Hope you get it sorted out! 🤙🏼🍻
 
Likes: rlbreakfield

Kisssofdeath

Sergeant of the Hide
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Minuteman
May 9, 2018
187
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South Carolina
#15
When I use my 7.62 Specwar on my 5.56 SBR I get a shift around one foot at 25 yards. When I use my AAC Ti-RANT 45M on my Zephyr II I get a shift around 5" to the right and 5"low at 50 meters. I have used these on other host without a noticeable shift.
 

TomH Tx

Private
Minuteman
Aug 17, 2018
27
12
6
#16
On my RPR 6.5CM, at distances further than 500 yards, when using my Silencerco Hybrid I generally have to add .5mils up more than what virtually any of the ballistics call for. But other than that, no real "shift" of POI.
 

Subwrx300

Gunny Sergeant
Belligerents
Jan 15, 2014
964
544
99
Cedar Springs, MI
#18
My Ultra 9 shifts as follows:
.25 MOA down in 6.5CM bolt gun,
.75 MOA down in 6.5CM gasser,
.8 MOA down in 224V
.75 MOA down in 223Rem.

All are within -+ .5 MOA left to right of POA vs unsuppressed zero.

6" seems like a ton....
 
Likes: Jeffd

EchoDeltaSierra

Low-speed High-drag
Online Training Access
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Jun 1, 2013
321
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Minnesota
#20
I've been messing this as well and what I have tested this with a Ruger American Rifle and R700, both 6.5CR with ASR muzzle brakes, and two 30 cal cans, a Specwar (heavy) and an Omega (light). We have seen a very noticeable offset with can on / off. With the Specwar on the Ruger, there's a 1.1 mil drop and .1 mil right shift. With the Omega on the R700, it's a .2 drop. From what it seems, this is the case wether we're shooting at 100 or 600+. This is one of a number of accumulating measurements on the "notes" pages in my DOPE book.
 

Darqusoull13

Private
Minuteman
Jul 5, 2018
55
24
12
#23
6" is definitely more than we see in virtually high quality bolt guns that do not have some other problem. The most likely cause is barrel threads / shoulder that are not perfectly straight and square to the bore. This can easily cause enough runout on the suppressor that the bullet doesn't quite kiss the endcap, but gets close enough to be "blown off course" and this often screws up accuracy some too.

Next would be harmonics / bedding, or other rifle-system issue, that is exacerbated by the suppressor. Typically we see this in bolt guns where a lot more is happening dynamically during firing, but we also see it sometimes due to an incorrect bedding job or something causing a weird barrel harmonic. This can often but not always be debugged by replacing the suppressor with a rigidly mounted weight of the same mass to see if it's replicable without the suppressor on.

We'd be happy to examine any or all of your system. We accuracy-proof-test suppressors all the time and it basically always comes down to the mount (in our case the CB or BA brake) being on the barrel somehow wrong.

Give me a call tomorrow and we can figure out what to look at next

Damn! That's unreal CS!