Suppressors New stock and huge suppressed POI shift

[tangodeltakilo]

I have a R700 LTR 308 barrel and action that I had threaded and an AAC 51t brake installed that was timed for my SDN6 silencer. I have used this setup for about 4 years with no issues. The barrel and action have been in an XLR evolution chassis and B&C stock both with a suppressed POI shift being about 2 moa down. I just recently upgraded the optic to a Leupold MK6 3-18 with seekin rings and stock to a Manners T3AF with mini chassis. After the upgrades I zeroed the rifle at 100 yards and then went to check POI shift suppressed and to my suprise it is about 20" up and 2" left.

The first thing I checked was for a baffle strike, none, everything looked good. Second was the mounting surfaces inside the suppresssor and on the mount for build up or debris. I scraped each with a copper brush and cleaned both, refired and same shift.

At this point I have no idea what else to check or what may be causing the 20" up POI shift suppressed. I would consider the barrel threading but I've shot the rifle for years suppressed same silencer with no issues. Does anyone have any ideas?

NOTE *It was about a year ago since I last shot this rifle suppressed and since then I have fired about 600-700 .223/5.56 through the suppressor. Also the stock is cut for a Defiance deviant action which per Manners the r700 is a drop in for. The rounds I have shot for zeroing and testing have been handloads (Nolser custom competiton 168gr w/ 43gr RL15).

Thanks

 

[chorizo]

Try removing it from the stock and then reseating and retorque it. I just had the same issue with my 338WM and it solved the problem. If the only thing that changed is the stock, then the stock is the issue (or at least the seating in said stock)

 

[tangodeltakilo]

I loosened the action screws today and retorqued them to 65in/lb for the front and 45in/lb for the rear per Manners. Still a 20" upwards POI shif with the suppressor on and also tested a diffirent bullet same results. This is driving me crazy as to why I am now getting a 20" high POI shift.

 

[FatBoy]

maybe I missed this, but have you checked barrel float with the can off and then on?

 

[fdkay]

Do you still have the old chassis or stock?
if you trouble shoot by putting the action in the old stock and the shift remains, it isn't the stock.
If it disappears, well then, you still have your answer.
I'm guessing there is something either in the barrel channel, or the action is torqued by the mini-chassis.
Not necessarily the fault of the stock, as the action can be out of round or warped slightly.
I ended up bedding my 700 in an XLR chassis for just that reason.

 

[flatland1]

I've got a Manners T4A with DBM mini chassis; even though the instructions from Manners list higher action screw torque values, I've stuck with my old standard values for M700/clone actions - 55 in/lbs front, 50 in/lbs rear. I use those torque values in any stock that's pillar bedded, or in B&C stocks with their aluminum bedding block. Only exception is with my 40X & XB 22RF repeaters in B&C #2015 stocks - I tested for accuracy with 55/50 in/lbs, and wound up backing off, down to 45/40 or even 40/35 in/lbs for best rimfire accuracy. And I shoot most of my CF rifles with TBAC Ultra 7, 30BA re-cored Ultra 9, 30CB9, and the 40X/XB with a SWR Spectre II - more than 90% of the time. Not seeing enough POI shift with any of these cans to matter much.

 

[chorizo]

maybe I missed this, but have you checked barrel float with the can off and then on?

This would be my next step also. The act of placing the suppressor on has something to do with the new stock as it didn't happen with the old stock (another good suggestion above would be to return the action to the old stock and see if you can duplicate it in the old stock......but check to make sure the free float in the new stock is not affected by adding suppressor first.)

 

[tangodeltakilo]

Unfortunately I do not have the old stock, just sold it before I realized this problem.

Last night I ran a brass cleaning brush through the suppressor in case something was stuck to one of the baffles or carbon build up causing the shift, haven't tested it yet but that is about my last idea. I called AAC today and discussed it with two tech employees. Their only explanation is possibly a baffle strike and offered to send a label to have it checked out and replace the core if there is a strike. Visually I did not see any noticeable baffle strikes but if the brass brush doesn't fix/help it I will send it to AAC.

I'll up date the thread once I get an answer.

 

[FatBoy]

run a business card under the barrel to the recoil lug with the can off and then with it on, do it again. Prove there is no difference before moving forward. Each step needs to be methodical or you run a real chance of missing something and frustrating the situation further .

I can't imagine a baffle strike unless you've changed something else that you don't have listed in the thread. a stock change isn't going to have anything to do with suppressor alignment.

 

[chorizo]

run a business card under the barrel to the recoil lug with the can off and then with it on, do it again. Prove there is no difference before moving forward. Each step needs to be methodical or you run a real chance of missing something and frustrating the situation further .

I can't imagine a baffle strike unless you've changed something else that you don't have listed in the thread. a stock change isn't going to have anything to do with suppressor alignment.

I concur. Nothing changed in the alignment and it sounds like it is repeatable. They only change to a previously reliable setup was the stock. ACC is of course going to focus on the can, but unless something changed with that from the previous successful 4 years of use why would that all of a sudden be the problem?

 

[Lowlight]

Silly question, but did you bother to re-zero the rifle ?

To me this sounds like you are comparing the change of stocks, vs the accuracy of the change?

Did you even rezero the rifle after switch or is this question, "why was there this big a shift ? "

You, a 20 MOA base only has a few thousands of a inch difference between the front and back which gives us 20MOA at 100 yards, so if you have a few thousands of an inch difference in how the barreled action sits in the stock, you're initial shots will be off and 20" is not really that unreasonable considering the big differences ?

V-block vs Bedded Stock, they will not line up the same from your old zero.

 

[missilemantdi]

I have had this occur when the suppressor backs off slightly. The shift is not enough to have the bullet damage a baffle but is enough that the baffle nudges the bullet, more of a glancing blow. Check for any trash or carbon buildup on the muzzle brake and inside of the suppressor where it mounts. You may not be able to tell if you are getting a collision unless you see some sparklers being ejected from the suppressor when you fire the round. This is assuming everything else is the same and everything is installed/mounted properly.

 

[chorizo]

Silly question, but did you bother to re-zero the rifle ?

He did. Quote from OP's original post: "After the upgrades I zeroed the rifle at 100 yards and then went to check POI shift suppressed and to my suprise it is about 20" up and 2" left."

This is what makes it such the mystery.

Upon reflection and re-reading everything, FatBoy nailed it, something changed with the suppressor/suppressor mounting that has gone either unnoticed or unreported in this thread. No other explanation is logical for such a large change.

 

[Long Range 338]

a 20 MOA base only has a few thousands of a inch difference between the front and back which gives us 20MOA at 100 yards, so if you have a few thousands of an inch difference in how the barreled action sits in the stock, you're initial shots will be off and 20" is not really that unreasonable considering the big differences ?

This seems like a very reasonable explanation of the 20" of shift and would be a good place to look especially after checking the stock and suppressor.

OP, you never mentioned whether the original scope was mounted in a mount or if you swapped out the rail and changed the MOA, we may be missing some info here if something else has changed besides the stock, optic, and rings.

Good luck, the pursuit of precision never ends.

 

[tangodeltakilo]

UPDATE:

So I called AAC who created a service ticket for me to send them the suppressor to look at. They provided a prepaid UPS label so I sent them the suppressor. They updated me when it arrived and when they shipped it back to me which totaled about 14 days.

Anyway I received the suppressor and it appears to be a completely new suppressor with my SN #. I had timed all my mounts and some ranged from zero movement to slight 1/16" rotation. After receiving it back some mounts are tighter while others slightly looser, but my main concern was on my 308 bolt. Before the suppressor had zero rotation on the mount and now it does has some, but most importantly is the POI which is now 2" poi shift down at 100 yards.

Apparently there was a small baffle strike, one that that I could not be detect visually looking through. Overall I am impressed with AAC's customer service I honestly did not expect the prompt and thorough response to fixing the suppressor.