Suppressors TBAC 30p on 308 AR

[on2wheels]

Have had an issue that is got me perplexed. New to using a suppressor so I know there will be learning curve to some extent. I have a TBAC 30p on a 16" AR308, threaded mount. I shoot 168gr Sierra BTHP factory loads and unsuppressed I have engaged targets to 1138 yd. I verified zero at 100yds unsuppressed, removed the FH and installed the suppressor. Suppressed the POI on the first round hit 3-1/4" low by 3" to the right, then the second 4" low and 2" to the right. Adjusted the scope (NF 2.5-10x32) accordingly and shot steady groups very well after that at 100yds.
Went back to the range on a different day, early morning, light wind, 3.2 MPH at 145 degrees, verified zero at 100yds suppressed, GTG from previous data log adjustments. Moved target to 200yds, adjusted elevation on scope U.4mils. The round hit spot on on elevation but the windage is 2" to 2-1/2" Right. Fired three more rounds and the same thing, right of the bull. Looking in the suppressor there is no evidence of baffle strikes, and looking through the barrel it is clear daylight with no shadows. Had to discount wind and being cool the parallax was minimal if any.
Talking with others that are familiar with suppressors it is common for the elevation POI to be adjusted but not the windage. I have called and emailed TBAC and Zak is great to work with and we are trying to work though this with different solutions. Shot with suppressor on, remove it, put it back on and do this exercise several times and see what happens to the POI.
My question is: Has anyone else had an issue with windage POI shift as you increase distance or am I chasing ghosts? At this rate shooting to 600-800yds lord only knows where the round will hit windage wise.

 

[Zak Smith]

For everyone else's benefit, the effects of a suppressor show up in a zero shift, which is apparent at your zero distance (eg, 100, and proportionally downrange). Outside of the very slight change in MV, the bullet once it's at 100 yards going to 200 doesn't know if it was sent through a suppressor or not.

 

[on2wheels]

Zak... You have been very helpful and talked me through each step and this posting is by no means disparaging words about TBAC as I researched your suppressors for quite awhile and gained the highest regard for your equipment or I would not have purchased it.
As stated during our off line conversations I do not understand why this is happening nor do others here in Arizona that sell TBAC and work with suppressed firearms. This is becoming a real head scratcher. I have even contacted the AR manufacturer and queried them as you recommended and they have no recollection of service requests for POI windage shifts when using a suppressor, and as well as a gunsmith in Phoenix to verify concentricity of the threads to the barrel if need be.
At this point before I go to the range and start sending rounds down range I want to get as much information I can from individuals that may have experienced a pattern of shift and found a solution on their own. I know we have conversed through emails and you have made very strong suggestions that I will incorporate to narrow this problem. As soon as my work schedule allows time to go to the range my plan now is to invest in, or borrow a solid shooting rest, set up 2 targets on each stand, one for unsuppressed and 1 for suppressed at 100, 200yds marks. Verify POI and windage shift, record, dial in accordingly and then shoot with the suppressor on, remove it, reinstall, shoot, remove and do this exercise several times as you suggested. When complete with that I will do as you recommended, pick a point out past the range and shoot to the backdrop and see where the impact is. I would even like to go as far as find someone with a 30P and use theirs and see if anything changes in windage POI or as you suggested put mine on someone else gun and see what results they have. I have to find out the root cause of the shift and correct it even if it means sending it back to you as you suggested for your evaluation and testing. I am hoping that strapping this baby down and removing all human error and running this exercise will alleviate and verify that the suppressor and rifle are good to go or verify that more investigation is necessary.

I am very satisfied with your and product and customer service, which should be a benchmark for so many other companies in America, and to others reading this post understand that my problem with my equipment should in no way should dissuade anyone from trusting that TBAC will provide them a high quality product with the backing of professionals, I do and will continue to.

 

[Zak Smith]

Just remember that a 10 mph cross for your load might be 3/4" at 100 yards (in range of group size error depending on rifle), but at 200 that same 10 mph cross might move it 3" or more.

 

[on2wheels]

Understand what you are saying regarding the wind. I am going to be looking at running this exercise on a calm morning almost the same conditions as the before. I want to minimize all the variables to get a true baseline of performance.

 

[on2wheels]

Well I heard back fro Zak At TBAC. I sent the 30P-1 to him for his evaluation and after testing it out at his range it is 100% spot on. During the time Zak had the suppressor he ask me to send photos of the threads and in particular the shoulder where the suppressor mates to the barrel. Through his review of the pictures and the termination at the shoulder he found that is the likely culprit to the windage shift I am having at extended distances. The suppressor is on its way back and a trip to the gunsmith is already scheduled to correct Zak's observations. When this work gets completed and I have time to get to the range I will report back with the update of the POI shift.
Thank you Zak for your hard work and concerned efforts to help me solve the problem. This is one standup company.

 

[Zak Smith]

For everyone else's benefit:

The first thing to check if the accuracy is not there, if accuracy is inconsistent, or if the POI shift is large (like over 10 MOA) is that the rear surface of the suppressor has full 360-degree contact directly against the shoulder that is behind the threads on the muzzle.

EG, like this, with no gap or "air" visible between the can and barrel

The reason can usually be found simply examining the muzzle threads on the rifle and visually comparing them to the thread-spec diagram. The most common reason is that the undercut ("C" and see "Detail E") is not set up right.

 

[on2wheels]

Well the advise from Zak regarding the shoulder of the barrel was exactly the problem. As you may recall Zak asked that I send him a picture of the barrel particularly the shoulder were the threads terminate. His critique was spot on and the barrel went into the smith and was modified per the detail Zak posted.
As I stated in my beginning post I was having problems with a windage POI shift as I increased distance and was not comfortable sending rounds downrange and not trusting the equipment enough to know where they were going.
Here is a picture of the results of the 200 yard suppressed string. The first one at the lower right had me going again because that is POI is exactly what lead me to question the equipment with the POI shift in windage being about 2" to 2-1/2" right. Then I stopped and remembered what Zak said after you shoot awhile... "Check the can to make sure it is tight against the barrel". Well once again Zak was spot on, the suppressor was loose, tightened it up and you can see from the target the rest is history and the problem has been solved.
So in closing I have to say as I said that many many thanks go out to Zak and the crew at TBAC for helping me get to the root problem and it was my equipment not TBAC that was causing the POI shift, and to the gunsmiths at Wright Amory at C2 Tactical in Phoenix that not only knew exactly what Zak was talking about and took the barrel in on Saturday morning with a quoted price to turn it down and said it could be ready the same day but really look for it on Tuesday after Memorial Day because of the backlog. Well I got a text message about 45 minutes later the barrel was done. Headed back to Wright Amory to pick the barrel up and they charged me half of the quoted price. So to anyone in the Phoenix area please check out Wright Armory, stand up people and quality service .
Many thanks to all of the professionals that help me find the root cause of the problem, get it corrected and back on target.
So in closing I will say again as I said earlier in the thread:

Zak,

I am very satisfied with your and product and customer service, which should be a benchmark for so many other companies in America, and to others reading this post understand that my problem with my equipment should in no way should dissuade anyone from trusting that TBAC will provide them a high quality product with the backing of professionals, I do and will continue to.