AAC 5.56 Ammo Evaluation

[markm]

I won't even shoot the existing load from the factory in any gun for any reason. Too unsafe. We had problems in 5 ARs with nominal 5.56 chambers.

I still want to shoot the reduced load in my WOA Wylde chamber to see how that thing handles it.

[bfoosh006]

I won't even shoot the existing load from the factory in any gun for any reason. Too unsafe. We had problems in 5 ARs with nominal 5.56 chambers.

I still want to shoot the reduced load in my WOA Wylde chamber to see how that thing handles it.

I REALLY want to know what propellant is being used.

[markm]

I REALLY want to know what propellant is being used.

Who knows if it's even a retail or canister grade powder? I'm really thinking they mixed propellants of different burn rates/Lots. Pappabear read a guy with 150 fps spread in his velocities.

It's like some idiot topped off the hopper of TAC type powder with an H335 type powder and God only knows what velocity each individual round might yield.

[bfoosh006]

Who knows if it's even a retail or canister grade powder? I'm really thinking they mixed propellants of different burn rates/Lots. Pappabear read a guy with 150 fps spread in his velocities.

It's like some idiot topped off the hopper of TAC type powder with an H335 type powder and God only knows what velocity each individual round might yield.

I can't imagine AAC uses anything but Bulk ( USGI'ish ) powders for the 5.56 77gr OTM loads... It is my understanding that Canister / across the counter, powders aren't practical for massive loading. The canister powders are held to a different standard then the Bulk powders. IE the canister powders HAVE to met the burn rates of published consumer data.. EVERY time.
Yes, there can be SLIGHTLY different hotter or slower lots, but in is typically within the "spec".

Bulk powders ( a train car load worth ) , like Uncle Sam uses, is batch tested for burn rate, and then the powder charge weight is determined by the burn rate results.
It is a lot harder then most people realize to produce the same Burn rate every day, 100% of the time.
Same thing as fast or slow barrels... If some one could make a barrel 100% identical , everytime... they would be rich.

Moral to the story is... I seriously doubt someone dumped some TAC ( etc ) into a batch, Lol... if that was the case, you'd likely see many more high velocites, not just the random ones. Basically, powder doesn't get blended again from the pile ( ? ) to the "powder hopper".

And I get the frustration from the people having issues... so this post isn't trying to cause an argument.... just still trying to figure stuff out.

I still have yet to have a blown primer or function issue with any of the AAC 5.56 loads.

Provided I get time this weekend, I have a bunch of Chrono work to do. This includes the current 24.5gr 77gr OTM.

FWIW, other ammo, Norma MLE .223 BSB 64gr, AmmoInc. Blueline 64gr BSB , Various 75gr and 77gr ( S&B, Frontier, current IMI, PPU ) and some Swiss P 69gr Match.

[markm]

It is a lot harder then most people realize to produce the same Burn rate every day, 100% of the time.

I have no doubt that this is true based on the lot changes I've realized in retail powders. The ball powder in this ammo should meter fine, and I don't think I've found any charge weight variances that struck me as odd. I should pull and weigh 10 random though. I have a ton more to pull down.

The primers seem stabile. So that leaves me with the problem being with the output charge somehow. Terrible velocity spreads and SDs.

[Rogue556]

***I have this cross posted elsewhere, but figured I'd drop this here to add to the information that others are providing.***

I had a chance to chrono the AAC 77gr TMK and directly compare it to some 2018 manufactured Black Hills 77gr TMK. I didn't have a chance to focus on shooting groups, but the ACC had most rounds touching at 50 meters. Black Hills wasn't quite as tight, but that could've been on me.

Here's a few pictures of the AAC next to the Black Hills for comparison.








Chronograph: MagnetoSpeed V3

Temperature: 75.9°F

Barrel: Centurion Arms 12.5" Lightweight Hammer Forged (Carbine). Surefire SF3P flash hider w/ Surefire Mini 2 Suppressor.


AAC chronograph results:

1. 2488
2. 2491
3. 2484
4. 2469
5. 2512
6. 2483
7. 2466
8. 2505
9. 2499
10. 2496

Average: 2489

Standard Deviation: 14.6

Lot Number: SCL1CF051


Black Hills chronograph results:

1. 2575
2. 2626
3. 2566
4. 2565
5. 2575
6. 2557
7. 2567
8. 2563
9. 2589
10. 2606

Average: 2578

Standard Deviation: 21.9

Obviously not a huge sample size, but hopefully this means they figured out what was going on before rolling out the TMK.

[Pappabear]

Looks like you did just fine. I would be thrilled with that outcome. Congrats
PB

[markm]

That's nice. I'd feel comfortable if the load we're fighting was slower than BH rather than WAY faster. I'd love to know what went wrong with the 77 OTM batch. Definitely powder related since every other component works fine without the original powder.

[markm]

I decided to quit messing with the powder in this stuff. All my rework is going to be with VV N135.

I'm going to get some crappy FMJs and build a reduced load to use the AAC powder. I'm too cheap to toss it out... especially with component prices as they are. So I'm making some short range blaster ammo with a lot of room for pressure spikes.

[ViniVidivici]

Best thing to do...I wouldn't want to waste the powder either.