300 Blackout Subsonic accuracy a joke???

[Kill By Number]

I'm glad to see I'm not the only one with MAJOR issues when adding a suppressor to my rifle.

I had a post earlier about it: viewtopic.php?f=141&t=94169

I haven't posted more about it because it's still being diagnosed. But, the latest, in my case, is:

1) Suppressor + Upper sent back to suppressor manufacturer. They identified a (potential) issue with the barrel threads, worked around it, shot decent groups.
2) Upper was returned, I shot it, and had horizontal stringing suppressed. Worse, subs looked like they were going in at a 45 degree angle.
3) Took suppressor + upper to FFL. They shot it with my handloads and factory. NO ISSUE with accuracy or keyholing.
4) I shot it, and again had horizontal stringing suppressed (although not as bad). Rounds were going in almost horizontally at 25 yards when suppressed. Moved the target out to ~40 yards - all holes were good (circular, no signs of tumbling) but a 12" 5-shot spread (when suppressed).

So, a different FFL is going to shoot it tomorrow. If they don't have issues, but I still do, then the FFL has asked to video tape me magically making rounds keyhole. To take as many variables out as possible, half of the tests I conducted in #4 were with MBUIS. Even at 50 yards, I got a respectable grouping (4 shots almost touching, same elevation) UNSUPPRESSED.

I'd show pics, but its beyond embarrasing...

My brother in law had a 9mm SBR that had crazy bad accuracy with an AAC TiRant 9 and an AAC Evo 9 but shot great without the can. We even had a machinist build a 9mm rod to place through the barrel and silencer to show it was concentric (not the barrel's fault). He sold it from frustration so we never figured it out. That same silencer works great on 9mm pistols. I would encourage you to always shoot 10 shot groups, because his would put 3-5 in one spot then put another 3-5 seven inches away in a nice second group (can be very frustrating trying to diagnose with 5 shot groups only). Good luck and I'll try to keep you posted on what's causing the issues with the SDN-6 / 300 blk combo.

[RDA]

My brother in law had a 9mm SBR that had crazy bad accuracy with an AAC TiRant 9 and an AAC Evo 9 but shot great without the can. We even had a machinist build a 9mm rod to place through the barrel and silencer to show it was concentric (not the barrel's fault). He sold it from frustration so we never figured it out. That same silencer works great on 9mm pistols. I would encourage you to always shoot 10 shot groups, because his would put 3-5 in one spot then put another 3-5 seven inches away in a nice second group (can be very frustrating trying to diagnose with 5 shot groups only). Good luck and I'll try to keep you posted on what's causing the issues with the SDN-6 / 300 blk combo.

Thanks for sharing that experience, very interesting and as you put it, very frustrating. I like to shoot five shot groups but will shoot ten and even twenty at times to see what happens with a larger cluster.

[wildfowler]

Any ideas on what is happening here???

Does the AAC ratchet lock tight into the last tooth of the mount? I had to hone the surface of the mount to get mine to lock up tight which improved my accuracy. But it was not as bad as yours to begin with and was not as inconsistent as your target.

On another caliber/suppressor combo of mine, I was getting baffle strikes that resembled what your target looks like. Thing about it was that I could not see any evidence within the suppressor that anything had happened. There was no copper shavings on the baffles or end cap that could be see or emptied out of the can.

I don't know if you specified? Shoot without the AAC suppressor to isolate the cause. Try a different mount if you have access to one.

Edit: how does other ammo shoot through the AAC?

[Kill By Number]

We tried black hills, gemtech and silencerco, all bad accuaracy with the AAC in .300blk, BUT it shoots on a 5.56 rifle great so hopefully its just the mount. We've got another 51 tooth mount to try out next time we go.

[certifiable]

AAC 16" pistol gas AR, FA BCG, JP SCS with 3 tungsten weights and yellow spring.
10 round groups shot at 100 yards using 4x magnification and all rounds were loaded on my Hornady LNL AP press.

[Tom12.7]

Was the design intent of this cartridge to be be the best bench rest cartridge ever? Obviously it wasn't, it had other criteria that was the driving goal. It works better than most in it's own intended role and does it well. It can have more than acceptable results in it"s intended uses, and is more than adequate for that role. There is little debate that there is another commercial cartridge that is better overall for its intended application for short barrels with and without cans in supersonic and subsonic applications

[Dr.Phil]

There is little debate that there is another commercial cartridge that is better overall for its intended application for short barrels with and without cans in supersonic and subsonic applications

Is this a typo?
If not, what is a better commercial cartridge that works better for short barrels with and without cans in supersonic and subsonic applications?

As to the groups that certifiable posted up, those are a good representation of what one can expect from an average off the shelf 300 BLK @ 100 yds.
Tighter groups are definitely doable, buy advanced reloading techniques and accurizing of the rifle are usually needed.
If I had to put out a blanket expectation of what a new adopter to 300 BLK should expect, it would be 1.5" to 2.0" accuracy @ 100 yards with quality subsonic / supersonic ammunition.

An interesting observation that I made when doing some extended 300 BLK testing, is that 300 BLK has a much more consistent bullet dispersion out to 300 yards than 5.56.
Of course this shouldn't be too much of a surprise to ballistic aficionados, the ballistic difference between the .308 caliber and .224 caliber projectiles makes the 300 BLK more tolerant to environmental influence.

[TB2BLAZER]

Well I was planning on building a 300 blk but you are right OP there is hardly and info on 100 yard shots. That makes me a bit hesitant to build one if it won't hold close to 2 minutes at 100. Im not looking for crazy accuracy but if im gonna pay $300 for a higher quality barrel it better shoot. I did see a video on youtube of a guy getting consistent hits on steel at 750 meters but then again it could be crap. Could barrel manufacturer have anything to do with the discrepancies? Or perhaps most 300 blks that I have seen have not been setup with match triggers, precision scopes, or accuracy enhancing stocks. It's hard to shoot very accurately (for me) at 100 yards with stock triggers, eotech optics, and collapsible stocks. I would really love to see some more good 100 yard groups.

[Kill By Number]

Well I was planning on building a 300 blk but you are right OP there is hardly and info on 100 yard shots. That makes me a bit hesitant to build one if it won't hold close to 2 minutes at 100. Im not looking for crazy accuracy but if im gonna pay $300 for a higher quality barrel it better shoot. I did see a video on youtube of a guy getting consistent hits on steel at 750 meters but then again it could be crap. Could barrel manufacturer have anything to do with the discrepancies? Or perhaps most 300 blks that I have seen have not been setup with match triggers, precision scopes, or accuracy enhancing stocks. It's hard to shoot very accurately (for me) at 100 yards with stock triggers, eotech optics, and collapsible stocks. I would really love to see some more good 100 yard groups.

As the OP, I have to admit my problem is suppressor / mount related. With another silencer I was able to shoot 1-2" groups with Silencerco factory ammo. Since posting this thread on a couple of sites I have seen more info on subsonic accuracy posted than I could find anywhere online, so I'm glad I did it. It was just odd no one seemed to be posting any subsonic groups previously.

[Tom12.7]

There is little debate that there is another commercial cartridge that is better overall for its intended application for short barrels with and without cans in supersonic and subsonic applications

Is this a typo?
If not, what is a better commercial cartridge that works better for short barrels with and without cans in supersonic and subsonic applications?

As to the groups that certifiable posted up, those are a good representation of what one can expect from an average off the shelf 300 BLK @ 100 yds.
Tighter groups are definitely doable, buy advanced reloading techniques and accurizing of the rifle are usually needed.
If I had to put out a blanket expectation of what a new adopter to 300 BLK should expect, it would be 1.5" to 2.0" accuracy @ 100 yards with quality subsonic / supersonic ammunition.

An interesting observation that I made when doing some extended 300 BLK testing, is that 300 BLK has a much more consistent bullet dispersion out to 300 yards than 5.56.
Of course this shouldn't be too much of a surprise to ballistic aficionados, the ballistic difference between the .308 caliber and .224 caliber projectiles makes the 300 BLK more tolerant to environmental influence.

It's that there's not one cartridge that does better in that regard compared to the 300 Blackout in my posting.