Suppressors Extreme POI shift from AACSDN6

[LWS]

I am having some extreme POI shift from my aacsdn6 and ive determined that it is a very light baffle strike, but now im wondering how to fix it?

heres my setup:
remington 700 aacsd 1:10 twist w/ an AAC 51t brakeout quick detach suppressor mount

ammo:
Federal sierra gold medal matchking 168gr bthp

Here is a 3 shot group shot of a harris bipod @100 yds for referencing POI shift


I then Attached my can and shot @100 yds again with nothing on paper. I moved to 50yds and shot 10 rounds with nothing on paper. I just couldnt believe I wasnt hitting paper at 50yds! thus the reason I dumped 10 rounds at it!

I then moved to the 25 yd range and shot this group below. Its important to mention that I was aiming at the #7 at the bottom of the target.


Ilooked down the aac can and saw no visible baffle strikes. Then after close inspection of the tip i found a very very faint copper mark that barely shows up in the picture below.


So what do you think the problem is? im thinking thread concentricty or maybe the muzzle brake is out of spec. Muzzle mount was timed using aac provided shims.

 

[Portsix]

I am in the same boat, with their Cyclone direct thread. Massive POI shift. They thought it was the fact that I'm shooting a 24" barrel. But upon really close inspection, there is an ever so slight rub on the exit of the suppressor.

Hmmm...

 

[Arrow 4]

The first thing I would do is get a bore rod/gauge and check the concentricity of the threads on your barrel.

 

[ZombieMonkey]

Two things that AAC will likely want you to verify before sending it in for inspection is that the can or muzzle device has in fact shouldered up to the barrel properly and that the threads are concentric to the bore of the rifle. If your threads are cut to to spec and these two things check out the next step would be to contact AAC.

 

[jasonfaz]

Yeah, that doesn't look like a baffle strike to me at all. You'll see that it's very common to get marks from residue on your cans and if you do ever have a baffle strike (or in your case what might be an end cap strike) it will be clearly noticeable. I'd also check your optic and mount to make sure there wasn't a shift there that would throw anything off. Who mounted the brake? Make sure it isn't loose as well.

That 25 yd group looks like your projectiles are tumbling - which would imply some stabilization issues are occurring. They're not hitting the target very clean. That's definitely a larger POI shift than what is normal in any can I've seen. Something's up for sure...

 

[Rstrick0352]

Tag

 

[Portsix]

Update:

So I took my gun and can over to Tornado Tech, since they're local and had done the threading for me. Everything on the rifle end of things looked great. They threw the can on a lathe, and spun it slowly. Sure enough, you could see the exit end of the can inscribing lazy circles. So, clearly my issue is manufacturing issue with the can (e.g. threads not square to the bore axis). Waiting to hear what the folks at AAC advise for next steps.

 

[ZombieMonkey]

You don't happen to have a second mount do you? It may also be a bad mount. Will be curious to see what the culprit happens to be.

 

[culater]

Do you polish the mount sholder to get out the wobble, from the can not getting to the last tooth.That may help

 

[jasonfaz]

You don't happen to have a second mount do you? It may also be a bad mount. Will be curious to see what the culprit happens to be.

Exactly what I was thinking. If it's the threads, why wouldn't it be the mount that has the issue rather than the can? If it was a direct thread can I could see the can being the culprit. But considering the SDN-6 is a QD can, I'd think it'd make sense that the issue might be coaxial alignment between the brake and the bore rather than the can and bore. Curious as well to see what it ends up being after it's all said and done. Keep us updated if you don't mind LWS.

 

[sierracharlie338]

I have an issue with the cyclone. On one rifle I have a 2 MOA shift low from suppressed. But on another rifle there is virtually no shift. Strange.


Sierracharlie out....

 

[Portsix]

Will do guys. Just to be clear, my POI issue is with the AAC Cyclone (direct thread). The OP had the QD can.

 

[LWS]

Thanks for the replies guys. I do have a spare QD mount, but I just put it on a 24" remington 700. Im praying that the 24" 700 wont suffer from the same issue. Im thinking if the can has no problems on the 24", then the problems lies with the aacsd 700 barrel or mount. I am for sure bringing the aacsd to a local rifle gunsmith so concentricity can be checked on the aacsd.

 

[jasonfaz]

My bad portsix, I meant to ask LWS to keep us updated. Post edited.

LWS, I think that's the right way to go. It has to be a concentricity issue and with a QD set up that would insinuate the problem is either the barrel or mount. FWIW, I've seen better, albeit only slightly better, performance with the 51T brakes over the Brakeout and flash hider. Might want to pick up a brake and try that. Comes with the necessary shim kit, rocksett, etc. Let us know how that 24" runs!

 

[LWS]

My bad portsix, I meant to ask LWS to keep us updated. Post edited.

LWS, I think that's the right way to go. It has to be a concentricity issue and with a QD set up that would insinuate the problem is either the barrel or mount. FWIW, I've seen better, albeit only slightly better, performance with the 51T brakes over the Brakeout and flash hider. Might want to pick up a brake and try that. Comes with the necessary shim kit, rocksett, etc. Let us know how that 24" runs!

lol funny you mention the differnet brakes. Im actually putting a 51t brake on the 24" instead of the 51t brakeout. I should be able to hit the range friday or saturday and update everyone. thanks again for all the comments.

 

[Portsix]

Quick update:

AAC has been great. I told them what I learned about the suppressor being at fault, and they immediately sent me a return UPS label for me to send the can in with. Great service so far.

 

[LWS]

Quick update:

AAC has been great. I told them what I learned about the suppressor being at fault, and they immediately sent me a return UPS label for me to send the can in with. Great service so far.

Keep me updated on what their turn around is on your suppressor being fixed. I may have to follow the same route.

 

[BurnOut]

Portsix- I'm glad to hear that AAC is standing up for you. With the rep that they have gotten over the last couple of years, I have been concerned about the service that I could expect if I ever needed assistance with my own SDN-6, but it looks like this could work out well for you.

 

[LWS]

Well guys I have good news! here is a groups shot out of my 24" .308 rem 700 using an AAC 51t brake. Aiming at the center produced this 4 shot group. So the SDN6 is good to go and the issue now resides in either the muzzle attachment on the AACSD or the factory threading job. I still havent brought it to a Gunsmith yet.

 

[TGagnon]

A gunsmith in CO springs threaded a 308 varmint barrel I had laying around and didn't do the job correctly. This led to me having to find a way to get the shoulder at the end of the threads re cut as they were somehow cut off axis to the bore. threads, thank god, were loose enough fit that recutting the shoulder fixed my problem and allowed me to go back to shooting. AAC was great during the entire process sending me information on thread dimensions and how to inspect the threading job as well as other information and help. My SDN-6 was my first center fire can and my favorite/most used can. Now I have a strict policy of threads only being cut on my barrels through head stock dialed in off of bore with range rod or indicator on bore in a spyder.

 

[LWS]

A gunsmith in CO springs threaded a 308 varmint barrel I had laying around and didn't do the job correctly. This led to me having to find a way to get the shoulder at the end of the threads re cut as they were somehow cut off axis to the bore. threads, thank god, were loose enough fit that recutting the shoulder fixed my problem and allowed me to go back to shooting. AAC was great during the entire process sending me information on thread dimensions and how to inspect the threading job as well as other information and help. My SDN-6 was my first center fire can and my favorite/most used can. Now I have a strict policy of threads only being cut on my barrels through head stock dialed in off of bore with range rod or indicator on bore in a spyder.

Local gunsmith said he would check the shoulder while checking concentricity. I hope a shoulder cut is all it needs.

 

[LWS]

Well gunsmith slapped the AACSD in the lathe and indicated it. The shoulder was way off and the muzzle device was no where near concentric, so I told him to chop and redo the whole thing! went ahead and purchased another style of the 51t mount. Originally i was running the 51t brakeout system. I am now running the full 51t muzzle brake. I run that same 51t brake on another one of my remingtons with great results.

I know there has been alot of talk about AAC supressors backing off one tooth on the 51t after mounting it. The full brake 51t mount i have locks up super tight with no backing off or play. the 51t brakeout model had the 1 tooth backoff issue. Im hoping the new mount solves this issue.

 

[PRDRIVER]

The ONLY NFA item that I regret purchasing is my AAC M4-2000. It took me 10 mounts ($1000 in mounts) to get one that timed properly with my particular suppressor. With every mount but the one that timed perfectly with my M4-2000, I saw my AR open up from a 3/4 MOA rifle to a 5 MOA rifle. On all the mounts that were not timed perfectly, the suppressor would back of to the first locking tooth on the mount and the accuracy went out the proverbial window. AAC treated me like crap back when I had issues. After a couple posts in recent years regarding my experience AAC has reached out and offered to help. But I now have other 5.56 cans that I like more than the AAC and with my one good mount, the AAC is basically permanently attached to my 10.5" SBR.

I picked up an OPS INC 12th model (same as the new Allen Engineering AEM5 suppressor) after having issues with my AAC. The difference in customer service is night and day. Ron Allen - OEM manufacturer for Ops Inc and manufacturer of the Allen Engineering suppressors is a top notch guy and takes care of his customers. Allen Engineering cans offer great noise reduction (I have yet to hear a better sounding suppressor on an AR), No POI shift, significantly less blow back than other 5.56 suppressors and the Allen Engineering version is very reasonably priced.

I have some customers that are ex special forces that have used the AAC m4-2000 and the Ops inc 12th along with other suppressors. When I have inquired which 5.56 suppressor was their favorite one to use, everyone of them has told me it was the OPS 12 (AEM5).

I am an FFL/SOT and have shot a number of suppressors (YHM, AAC, Surefire, Ops Inc, Allen Engineering, Thunder Beast, SWR, Silencerco, etc.) The Allen Engineering cans are my favorite suppressor for the AR platform.

 

[Strykervet]

One thing it could be is bullet stabilization. Check the weapon against a cardboard at a few feet and another at a meter and maybe a third a few meters past that, all lined up in front of one another. Look for keyholing or anything other than a perfect round hole. Short barrels and weapons firing bullets weighted far in excess of the twist required to stabilize it can cause this problem. Do this with no suppressor and try it with all the rounds you use. If all the holes are round, try it with the can next and see if it wiggles when you put it on, because...

SDN-6, it's the damn mount most likely. I have several mounts and every damn one locks up different. You have to take the fucking mount and chuck it into a drill press and use an angle and lapping tool or file to gently remove metal from 45deg. bevel just over the teeth (most precise DIY way sans a lathe). Remove small amounts at a time, check often. When it fits tight and locks up with no wiggle, you should be good to go. Assuming the mount/barrel relationship is fine.

Every single rifle I have using this can has a POI shift, some worse than others, but all fixed degrees better for the most part by tightening up the mount. Accuracy increased as well. To give you an idea how bad, one rifle locked up perfect while one wiggles A LOT and you can even see the can eclipse the bore (and several in between). And AAC doesn't give a shit and they know! I've even heard of this being so damn bad that folks (more than a few) have had baffle strikes and end cap strikes firing 5.56 through them.

Note lots of people have problems with these SDN6 cans. Great, great cans, shitty, shitty mounts and AAC quit caring about the 1000th call, yet never stopped the practice. Anyway, you can unfuck it, just don't let AAC know you did it, keep an unmodified mount laying around in case you have to send it in some day. They'll cancel the warranty if you send them a modified mount, but their warranty is shit if you don't modify the mount, so they want it both ways at your expense.

Lots of posts on here about how to fix this, but the idea using the press, angle and file or stone seems best to me. If it's a very small amount of material, that can be removed by hand with a file and blue or a sharpie.

AAC makes really great cans from great materials, but based on this experience and how they've chosen to handle it both short and long term, it'll be the last AAC product I buy. In fact, I've already got two form 4's in process and neither one has "AAC" anywhere on it. If I get another QD can, I'll take a look at Elite Iron's method, otherwise I'll just stick with thread on only from now on.