View Full Version : Objectively discussing AAC 51T cans and accuracy issues
Eurodriver
02-21-16, 15:07
I see this question get tossed around all the time, and I don't know where it comes from. I have two AAC 51T cans, one in .30 and .223 and both shoot amazingly well. Does using a 51T can affect accuracy negatively based on your experiences?
Yesterday,(I posted about it in this thread) (https://www.m4carbine.net/showthread.php?176594-500-yard-group-how-am-I-doing-update-post-46-0-5-MOA-at-560-yards&p=2271459) I shot a 2.79" 5 shot group at 560 yards with a rifle having an AAC 762SD hanging off the end.
I cannot possibly imagine that group being much smaller given my skill level, ammunition, and optic. Yet I constantly read that the 51T can is not for precision guns. :confused:
Where does it come from? Could it be improper installation? Overtorqued flash hider installation? Barrel threads not being concentric to the bore?
I only have a sample of two, but why does the "wobble" not affect me? I'm not suggesting folks go out and buy a 51T can. In fact, if I were buying a can today I would not, but I want to put this "myth" to rest...
Disclaimer: I don't own AAC cans.
With any precision setup I would think a quick-disconnect can would allow for more errors due to POI shift if the can is removed and replaced as well as wear of the teeth on the mount over time allowing the can to move slightly.
Of course any can is going to potentially alter your POI, but provided you know the difference and aren't removing and replacing the can regularly between firings, I see no reason the AAC can would be any more of a hindrance to accuracy shooting than any other manufacturer.
I own 6 AAC cans and have a .25 inch gun that wore a M4-2000 for years up until last week. I think in the precision world anything that moves is considered to potentially effect accuracy. Therefore direct thread was considered a better approach ( in theory ) to QD cans. However, IMHO, the AAC cans may twist ever slightly but change nothing ballisticly. Any change in POI is repeatable.
I really like my Thunderbeast can in the way their QD has a screw on feature. I recently bought a Sig can ( in jail ) that has a very sophisticated mount-adapter-brake that I look forward to reporting on. I think on average people don't shoot well and ....." It's that damn can".
I've personally read no threads where a guy shot groups with a AAC 51t can on, then took can off and there was a positive difference. It may well have happened, but I've not read it. But read 100 threads challenging the 51Tuphus!
I hope that sheds a spot of light. I'm sure others can offer more on the subject. I have 100% confidence in AAC cans for accuracy work. Even if it has slight wobble.
Eurodriver
02-22-16, 12:46
Thanks for the replies. That's interesting that we have all heard anecdotal stories (nothing first hand) of 51T cans affecting accuracy, but never seen it or read it first hand.
I have noticed POI shift with my 51T can mounted but it is A) repeatable and B) in some cases, negatively affected precision with the can off. Since 99% of my shooting is done suppressed this could have been due flinching from the increased noise and blast from the 51T brake (your brake, PB ;) )
I'll echo Pappabear's experience since I've shot all of the guns he's run. The 51t has never been an issue. Our shooting leans (almost obsessively) towards the precision end of the shooting spectrum.
I only have one 51T can but I have used it on 3 different guns with no real noticeable POI shift at all.
There is a slight wobble in all 3 but it doesn't affect anything.
I was able to shoot a 5 shot 3" group at 200 yards with a 14.5 middy topped with a T2 which is about as good as I've ever shot that gun.
Thanks for the replies. That's interesting that we have all heard anecdotal stories (nothing first hand) of 51T cans affecting accuracy, but never seen it or read it first hand.
I have noticed POI shift with my 51T can mounted but it is A) repeatable and B) in some cases, negatively affected precision with the can off. Since 99% of my shooting is done suppressed this could have been due flinching from the increased noise and blast from the 51T brake (your brake, PB ;) )
Great to hear your precision game is getting buttoned up. One of the most bizarre things we have noticed is how much weather, atmospheric conditions can effect DOPE. One week 1075 yards is 12 mils, the next it's 11 or 13. It often holds the same, but typically in the summer as our guns and ammo get hotter, so does our shots. All that considered, we have seen some crazy shit lately.
chasetopher
02-23-16, 12:28
As others have stated, I also see some POI shift with the 51t mounting system, but it is absolutely consistent/repeatable. With the SDN6 on an 18" barrel/rifle gas I see a repeatable 1.5" shift on vs off, with even less shift on my 11.5". (@100yds)
One abnormality that I do run into is on a .300blk barrel for a T/C Encore that sees a 6" shift UP with the can on, I'm sure this is attributable to the action locking mechanism having more weight on it. I only bring this up as an example of real POI shift, where any of the AR pattern rifles see fairly minimal shift in comparison.
Edit:
To clarify, I see absolutely no negative effect from an accuracy perspective(group size) hence the focus on the minimal POI shift.
I own two AAC 51T cans, SDN6 and a 556 SD and agree with whats being repeated here. While I wouldn't recommend the 51T system any longer, it isn't due to accuracy issues.
My SDN6 has had issues with latch failure and collectively has spent about two months at AAC for repairs, during the first weeks of the Freedom Group takeover.
While I wasn't happy with this, nor the months it took me to finally cash in $400 worth of damn the man rebates, neither of these issues really effected the performance of the can.
One lives on a Remington 700 AACSD, the other on an 18" Predatar. Both guns are easily sub-minute guns if I can do my part. Both suppress to my expectations.
Sure, the can's do wobble on axis, but anyone with a rudimentary understanding of how gears work (essentially all the latch is) would know to expect that out of the can, as I did before purchasing mine.
My only hesitation to recommend an AAC product at this point is the negative spin of innovation and originality Freedom Group has imparted.
They're both great performing cans that get more negative press due to the mounting system vs. positive press for actual performance.
First off I am not a employee of AAC or any of the Freedom group and have not done any work for them in over 5 years now. The following is not connected to AAC in any way. I also have not had contact with AAC in over 5 years so I do not have any insight to what is going on there any more.
I am the engineer that designed the 51T latch (originally it was 50T). The design was a compromise at the time since it was designed to be reverse compatible with the older 18T mount system so people could buy a new can and still use it on the older mounts. Part of the reason the reverse compatibility did not work out well was the latch spring had to be so heavy it would wear the teeth if the user just screwed it on without depressing the latch. My original design had 3 teeth on the latch instead of the current 2 teeth which was changed against my recommendation. The 3 teeth spread the spring load out better reducing wear on the latch teeth. The latch had to be a little softer than the flash hider because the customers would go nuts if they had teeth damaged/worn out and had to be replaced where as the latch was a much cheaper item to replace under warranty. The design goal of the mount also was having the ability to break it free from carbon freeze that many QD mounts experience. The stub ACME thread gives the user a caming surface to break the carbon buildup on the mount/suppressor interface. The stub ACME thread also is very damage resistant which was a major consideration when going after the military contracts. During firing, if you could "feel" the suppressor, you would feel that it is locked up very tight. This is due to the pressures generated by the gases. This can also be seen in other suppressor manufacturers like Gemtech's G5 QD mount. The can is easily deflected by pushing sideways on the muzzle of the can due to the spring being used to tension the can on the mount. When the gun is fired the can is forced against the locking lugs to be tight and as true as the mating surfaces are machined.
I have several suppressors using the 51T mount as well as the later 90T mount. I have never had any issues with accuracy and during testing we did not see any issues. I do not clean my suppressors or the mounts so after 1 day at the range there is no "wiggle" in those mounts that the tooth does not happen to perfectly lock up on.
Hope this helps to give some insight to the mount. If I were designing it over today it might be different and the 18T compatibility requirement should have been dropped right off the bat.
Mongo man, how have you been able to bite your tongue concerning all of the recent threads that delve into 51T topics? It's good to hear from someone with your level of first hand knowledge. I also have a certain amount of respect for someone who's been a member since 2006 and a post count of 107.
Well if pappabear, markm, and now mongo haven't put this one to bed, I don't know what would. :-)
My original design had 3 teeth on the latch instead of the current 2 teeth which was changed against my recommendation. The 3 teeth spread the spring load out better reducing wear on the latch teeth.
Excellent post, thank you for your insight! It makes perfect sense to go with 3 teeth - why did they decide to go with 2 teeth?
Thanks.
Well if pappabear, markm, and now mongo haven't put this one to bed, I don't know what would. :-)
Thanks for the vote of confidence.
This thread should be a sticky in NFA.
Great to hear your precision game is getting buttoned up. One of the most bizarre things we have noticed is how much weather, atmospheric conditions can effect DOPE. One week 1075 yards is 12 mils, the next it's 11 or 13. It often holds the same, but typically in the summer as our guns and ammo get hotter, so does our shots. All that considered, we have seen some crazy shit lately.
14 degree temp spikes in February? Thanks Arizona.
Mongo man, how have you been able to bite your tongue concerning all of the recent threads that delve into 51T topics? It's good to hear from someone with your level of first hand knowledge. I also have a certain amount of respect for someone who's been a member since 2006 and a post count of 107.
Well I don't get paid to do marketing for any company and its not my place to really answer questions for AAC (or any company I have worked for). I've done work for a lot of different gun companies and if I answered questions about each of the products I had some involvement in I would not have any time to do any work.
Unfortunately it seems these days with the internet those that love to make statements w/o any real knowledge of what they are talking about get more attention than they should. Keeping people's opinions about topics people do not know much information about seems to be a lost art. Having technical discussions is one thing but diarrhea of the mouth is another. I must admit over the years I have had a few occasions which I should have shut my trap as well so we are all subject to it occasionally.
As for my low post count, well I stick to NFA and technical forums on firearm design/manufacturing so I don't post much here. This is the only section of M4carbine that I read daily and even that I just look at topics and see if one interest me. Traffic here is pretty slow in the NFA section so my number of post is low as well.
You can see some of my work as well as my resume at the following links
http://weaponblueprints.com/
https://grabcad.com/mongo-3
Excellent post, thank you for your insight! It makes perfect sense to go with 3 teeth - why did they decide to go with 2 teeth?
Thanks.
It goes back to that damn reverse compatibility issue with the 18T mounts. Three teeth required even more spring pressure to retain on the 18T mount because it bridged more of the valley.
Hindsight is always 20/20 and dumping the 18T mount at the time did not seem like a viable option. Remember at the time it was designed the only other QD mount can was the Gemtech M4-96D which was subject to carbon locking (addressed in the G5 mount later) and possible spring issues due to heat (springs in suppressors are always a major concern because of the heat they are subject to, at least in center fire rifle calibers). AAC pushed the industry hard and we all benefited from it. Suppressors innovation pretty much stood relatively still for 30 years with Gemtech the only company that was offering any real innovation. Love him or hate him, Kevin Brittingham pretty much pulled the suppressor industry into what it is today. I enjoyed working with Kevin because he loved R&D and exploring new ideas. Getting a budget for R&D in most companies is worse than pulling teeth but Kevin devoted a large portion of AAC's capital to it. He also knew how to include aesthetics in designs that as an engineer we often over look. I'm sure Kevin would have abandoned the 18T mount and reverse compatibility to it if we knew what we did today.
Ive got an SDN6 and I think 6 hosts right now, 2 of them being dedicated precision rigs(6.5creed with JP barrel and 5.56 SPR with CLE Krieger barrel) and both are sub MOA shooters with the can on. BOTH mounts have "wiggle". Both have POI shift, but its repeatable. My best group ever(a .4moa group) was shot with the can on the 5.56 SPR.
On my 300BLK upper, the mount has no perceptible wiggle and very minimal POI shift. I can hit a 3" plate on command all day long from 100-150 yards with a red dot and subsonic ammo, which aint the most precise shot required in the world, but with a 2moa dot on subsonic 300blk it impresses most people. I have carbon locked the can to the mount on this gun, but I would guess that was 1500-2000 rounds of nasty sub sonic ammo. It came off with a strap wrench and luckily the mount stayed on the gun. Cleaned everything up with a small wire wheel on my dremel.
On my other hosts the same story un-folds. Little wiggle, still accurate, but has a POI shift.
Would I buy another can with a 51t mount? No. But not because I think its a crappy mounting system, its because I think AAC has gone down the shitter in the last 2 years and I wouldnt buy a single one of their products. My next can will either be a Dead Air or a Thunder Beast.
Something I did not mention, POI shift on most suppressors has more to do with baffles design than it does with the mount. If you use asymmetrical baffle design for gas shearing then you will most likely have some POI shift. Suppressors like OPS and Surefire, which is essentially a copy of OPS baffle stack, use a simplistic symmetrical baffle to achieve suppression. They use a lot of baffles to improve suppression where as other companies like AAC use, or used since I am not current on what they are using, symmetrical baffles with asymmetrical gas porting. Some of the other AAC suppressors use completely asymmetrical baffles.
chasetopher
02-28-16, 22:14
Well if pappabear, markm, and now mongo haven't put this one to bed, I don't know what would. :-)
Threads like this are what keep me reading, and help maintain my sanity amongst the rumors/lunacy. Thank you gentlemen.
While I've always seen repeatable POI shift using a SDN6 on a 5.56, using it on my 6.5 creedmoor boltgun caused a strange POI shift that would sometimes send flyers a few inches to the right, but sometimes not. I don't see any baffle strikes, but it scared me enough that I don't ever attach it to my boltgun.
diving dave
02-29-16, 10:31
Well, this thread has helped me make up my mind on an upcoming project. I have a Robar SR90 I've had for years, but some planned upgrades are threading the barrel for can use and updating the bottom metal.(It still has the old 700 BDL style internal mag) I have a AAC 762 SD, which I've been I've been using for 300BO,223,6.8, and 308...All semi autos with Blackout flashhiders. I was leaning towards a new can on the bolt gun, but not wanting to have to wait for the stamp. So I'm going to mount a 51T muzzlebrake on there and use what I have. When I get it together I'll update what the results are. Another side bonus, the money I was planning to spend on another 30 cal cal I think I'll get a Silencerco Osprey for my 45.....:cool:
Sample size of 1 AAC-762SDN6 on 4 hosts (3x556 / 1x762), no wobble after the mounts have some carbon on them, no decreased accuracy and repeatable POI shift.
I would have gotten a Saker 762 if it had been available at the time, but I'm completely happy with my SDN6.
Sample size of 1 AAC-762SDN6 on 4 hosts (3x556 / 1x762), no wobble after the mounts have some carbon on them, no decreased accuracy and repeatable POI shift.
I would have gotten a Saker 762 if it had been available at the time, but I'm completely happy with my SDN6.
Ditto
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.