Kind of a follow-up to this thread:  https://www.ar15.com/forums/armory/Baffle-strike-questions-/20-550547/

Anyways, had a baffle strike in a brand new Aero Precision Lahar-30K mounted to my Sig Rattler a few months ago.  Ammo was AAC 125gr FMJ.  Life got in the way and I didn’t get a chance to get out to really test the ammo to isolate my problem until about a week ago.

These were the results:

Attached File


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My plan was to get some heat into the gun with 90-120 rounds as heat seems to be cited as an underlying cause with this.  I didn’t make it through 2x 30rd mags before I started getting random shots flying all over while trying to shoot steel silhouettes at 50y.  

First target is the earliest lot of ammo.  As you can see, I’m getting horrible keyholes and projectile fragmentation.  Some of those oblong holes on opposite sides of the target were made with 1 shot, so I’m definitely getting frag.  Zero rhyme or reason to it, it was super random, but typically saw between 5-10 projectiles do this per 30 round mag.

Second target is the later lot of ammo I have.  Was not having nearly as many issues with this one, but as you can see of the 20 rounds I fired, I had 2-3x start flying sideways on me.

It’s not the gun or can.  This was all shot unsuppressed and I’ve got quite a bit of ammo through this gun of other types without issue.

Anyways, I’m already talking to PSA about this.  Their CS has always been slow, no different in this case, but I’d imagine they’ll get me taken care of.  That said, if people are shooting this stuff through their can, they need to know the risks so they don’t end up breaking stuff.

Lot #s for those curious:
*SCL3CA031*
*SCL4BJ191*

Thanks for the heads up!
I've heard of a lot of issues with the AAC ammo.
I'm going to stay away from it.

So… You’re shooting rifle ammo through a barrel significantly shorter than it was designed for with a twist rate way out of spec for the ammo (1:5 instead of 1:7-1:8) and then thinking the ammo is the problem/causing the key-holing/instability?

Edit to add: one of the basic lessons for shooting suppressed is to always test your rifle/ammo combo unsuppressed at 25m first to ensure you aren’t key-holing… now you learned why.


Edit2 to add: -I’ve seen mentioned before that <150grn can have problems with instability and jacket separation in the 1:5, particularly when warm/hot… maybe stick to 150-208 grn if you don’t want to rebarrel.

If you bothered to read, you’d see that I’ve shot other manufacturer’s ammo in the same weight class without issue, so no, it’s not specifically the gun.  This also is nowhere near an isolated incident with PSA/AAC produced projectiles, there are a number of other reports.  Many more with their 5.56/.223 FMJ loads, but there are a few with .300BLK.

I’ve also never had an issue with projectile instability with this gun.  Yes, testing it again with a new load would have prevented this and I shortcut that step.  Still, many people don’t, so consider this an awareness post for people shooting this ammo or thinking about shooting this ammo.

Lastly, 5”-6” .300BLK guns are starting to become a lot more common and fit well into the niche of a PDW with modern defensive loads.  Rattlers are institutionally used by a number of professional organizations.  This may very well be a case of 1:5 twist being too fast for the projectile, but given the prevalence of 1:5 twist .300BLK barrels (literally every single .300BLK MCX regardless of barrel length is 1:5), it should be noted on the product page in big bold letters if that’s the case.

@JTR

I’ve noticed aac  (110 grn at least )was about 100 fps faster than some other brands, I wonder if that is why you had the issue with aac and not with other brands? -I’ve shot thousands of rounds of  aac110 and some 125 aac iin   1:7: twist barrels and it’s shot better than ~9/10 other brands.  -As another poster above mentioned, aac also tends to load multiple different bullets in each grain offering, and the issue may be specific to certain bullets themselves so maybe we should keep better track of those details… I appreciate that you listed specific lots as that helps!

I haven’t chrono’d any plinking loads out of the Rattler, so I can’t say how close or far apart the AAC is from the other stuff I’ve shot.

In any case, as soon as D Wilson gets me my DD .300BLK barrel back, I’ll run the same test with an 8” 1:8 barrel and see if there’s any difference.

That would be awesome if you could use the same lot of ammo!

My Rattler will throw 150gr straight sideways like a tipped football into a 2 foot group @ 25yds.

Which loads?

@doty_soty

Any of the repurposed M80 (so not exactly 150gr, to be specitic) loads are a crapshoot, at least with mine. The lighter 300BLK specific ammo is a laser.