I'm sure some of you saw the thread in GD, but I wanted to see if maybe some folks in this thread could diagnose the issues.



https://nypost.com/2023/12/19/news/harrowing-video-shows-arizona-cops-in-deadly-shootout-with-alleged-kidnapper/

I'm really, really, really interested in the 6.75" SIG in 300blk, but this video is concerning.   Two these new 6.75"'s in 300blk malfunctioned, and that gives me pause.  On a side note, it looks like the perp had on body armor that caught quite a few rounds.  I'm not sure if subs or supers were used (sounds like subs, but rumor is supers), but the lack of penetration is also concerning. (Perp wearing level 4 maybe?)

Any insight would be appreciated.  I'm kinda banking on the TRO in Illinois being reinstated hopefully on the 3rd (foolish, I know), and would like to move forward in hunting down a new upper, but I don't want something that malfunctions this bad.

The mags look odd, could that be an issue?  Wrong gas setting?

I'd say Det 1's rifle took a shit from him bailing out of the car and causing damage to the mag.  Det 2 looks like the gun got struck

Looked like Det. #2 got a shot off, but then his gun quickly stopped and was ditched. Also looked like they were shooting suppressed and it could have been a wrong gas setting in combination with not enough lube. I don't know, just spitballing.

Looks like it could have been mag issues, as I saw trigger pull, but nothing happened.   Det 2 hit his mag, pulled the charging handle and still got a dead trigger which is why he switched to his sidearm.   I know subs are super finicky in standard AR mags (not 300blk specific mags).

There was a lot happening but it almost looked like a mag came apart and dumped its guts.

Looks like they're running a subsonic round.

Running heavier, longer bullets with GI mags can cause issues.  There's a reason why Magpul came out with their mags.

I'm sure there's more going on here but that's my unscientific guess.

Those dudes have really nice kit.

In the thread in GD, a poster mentioned he was told that they were running supers, but who knows.

Wrong gas setting plus bad mags?

Still curious to about the details.  It looked like D3 didn't have any problems with his MCX.

@killerb6 what did they say?

I'm a no body but it seems like a 6" 300bo AR up against a armored bad guy wouldn't be optimal.

If they are using 6.75" MCX's and good 110gr ammo, I would think supers would be Ok against IIIA armor at that range.  But I don't know if the perp was wearing level IV, or if they were shooting subs or some type of heavier supersonic round that didn't have the velocity needed...or was shooting through autoglass the issue.

I tend to think those were subsonic rounds.  In the end of the video, you can see the slugs lodged in the suspects ballistic vest.  Or what appears to be slugs.

I'd love to get more information if anyone has it.

In for answers.

Bump for any updates.  Still curious as to what happened.

Woah

I’ve fired alot of 300 blackout in suppressed MCX’s and the thing I’ve learned is to stick to ammo that functions well in the minus gas setting.I reload most everything I shoot and I pick loads that allow me to not ever even have to mess with the gas block unless the gun is EXTREMELY filthy and needs extra gas to cycle.

Yikes. Rifles malfunctions, subs not penetrating soft armor, I’d be reconsidering my load out. Glad they came out okay.

I haven't watched this yet, but here's one analysis.

https://youtu.be/O23f4wcX6jY?si=wJrIhrDhLF0u3ia3

Are we sure that these are the new ones?  Looks like the previous rattlers and not the LT ones, based on the receiver cuts right behind the handguard.

The guns are 6.75 inch tacops rifles. Essentially Virtus guns with a suppressor under the handguard.  Not rattlers.  They were never designed to be fired unsuppressed like the new 6.75 inch rattler LT is.

If those are the old ones, I'm feeling much better (at least about purchasing) a new SIG.   I thought those were the new ones, and I was beyond disappointed.  Still curious to see an AAR on this.

They don't work very well suppressed either....

What kind of issues did you have?

Officer 1 could have done a number of things in the scramble to get out of the car.  Hit the mag release, pull the charging handle back enough to get it out of battery, etc.  I can't tell.

Officer 2 had at least one *click* instead of a bang, which could be a feeding issue, ammo issue, maintenance issue, etc.  

Anyone recognize the magazines/extensions?

Holy shit, that guy is almost unwatchable.  I don't give a shit if he was there, can't watch that hyperactive, spastic delivery on his video.  Apparently his target audience is 12 year old's with ADHD.

You're absolutely right! I went back later and watch the video and it made me sorry that I had put the link here. He didn't know any more about it then we did from watching the video and he missed a couple of points that we have noticed. MEA CULPA.

Griff

Most of the issues are with subsonic rounds.   It is hit or miss on a lot of things...locking the bolt back on last round, feeding, picking up the next round....Just part of it with the 6.75.

Hard to be "beyond disappointed" when there is basically no clear idea of what happened or why.
I haven't poured over the video frame by frame, but I agree they are at the very least not Spear LTs, you can see that from the handguards.  They also look more like 10-11" guns to me, but maybe it is a Rattler length with a tucked can; that is hard to tell.
I can't even tell whether they are 5.56 or 300blk.

If 300blk...
Shirley they wouldn't carry subs in a patrol or SWAT type role?  With subs, you have a subgun, not a rifle.

At one point you can see one of the guys pull out a mag and see a loose round fall out as well, which to me says there was likely some kind of feeding issue and he was jammed.
Most subs I see today are now loaded too long to work in a regular 556 mag (they need the 300blk specific mags).
I would hope police who are well funded enough to run MCX's can afford to put more than two mags through them in training to verify they work with the ammo and mags selected.

I guess I got lucky.  I've had mine about 5 years with no issues.

That’s good to hear.  What suppressor, what valve, and which subs you running?

I’ve had issues with subs in both of the 6.75s I’ve had.  Admittedly I didn’t try a whole lot of loads, but I don’t have a need for them so it wasn’t really a priority.

Never had an issue with any super loads, though.

Yes.  The supers run fine…it’s the subs that has issues.   Oddly I don’t have as much issues with subsonic rounds out of the rattler as I have figured out which ammo to avoid, and definitely have no issues eating any kind of subs out of a 9” or 10.5” AR type rifles.

The 6.75 seems to be hit or miss with subsonic rounds for some reason.

I've used multiple suppresssors with the 6.75" MCX.  Off the top of my head:
SRD762
SRD762Ti
Nomad 30
Nomad L
Sandman S
Sandman K
Omega 36M short and long
Chimera

Nobody seems to be complaining about how supers run in the 6.75" MCX, so I'll focus on subs.

If I remember correctly (On my first cup of coffee), it came with the F01, and I acquired the F03 this past year.  I'm a handloader, so I loaded some things I expected to be marginal, and while there was some difference, I didn't think it was huge.

I use primarily 220gr projectiles, and handload most of what I shoot.  I have bought very little factory ammo since COVID, but I remember running the Sig 220gr Performance Elite ammo, and Lehigh 194gr ME factory ammo with no issues.  I may be wrong, but from some of what I read on gun/reloading forums, I get the impression that some of the ammo companies, have started focusing on quieter vs more reliable subs.  What I mean by that is that instead of sticking with gassier powders like Accurate 1680, they use faster burning, less gassy powders which are quieter, but may not produce enough gas to cycle reliably in all firearms.  I have an 8" bolt action 300 Blackout, that I use fast burning pistol powders with, to make it ultra quiet.  For my semi-automatics however, I stick with gassier powders that are more reliable.  Powders that I've found work well are N120, Accurate 1680, CFE BLK, and IMR 4227.  I only use IMR 4227 with the 220gr projectiles, it doesn't work as well for the 190gr Sub-X or 194gr Lehigh ME bullets.

I have found that the 6.75" is the pickiest MCX barrel I have for subs, but like all my firearms, I find what works well and stick with it.  In addition to my Tac-Ops, I use a 6.75" barrel in my Rattler vs the 5.5" it came with.  Even though some posting in this thread don't agree, after several years of comparing different barrel lengths, I've found that for barrel lengths less than 8", there is a significant pick up in MV per inch of barrel added.  I had hoped Sig would produce a 7.75" 300 blackout barrel too, but I guess for the time being we are limited to 6.75" or 9".  

A couple of other things I've found to keep the 6.75" MCX reliable, is that when shooting subs or subs/supers together, I keep my gas valve on "+".  The supers are a little gassier, but it operates reliably.  For supers only I keep it on "-".  If you have one, you already know this, but after several mags it can be hard to switch the gas valve with just your fingers.  It's best to set it for what you plan to shoot, and leave it there.  I also stick with Lancer and Magpul mags designed for 300 blackout.

Another thing I'll mention is that I tried an aftermarket trigger for a while.  Initially, I thought it was good, but after more rounds I found out it wasn't as good as the original trigger.  Sometimes, click and no bang.  I only bring that up because of what we saw on the video.  Don't bother asking me what trigger it was, because I won't disparage the company.  That trigger just wasn't right for the MCX.  

I'm curious about the functional issues from that video, but don't know that they are Sig's fault.  We don't know the condition of the firearms, condition of the mags, what mags, ammunition used, or modifications they may have made.  

Great write up!  Interesting about the trigger and am glad to stick with the stock trigger as it feels decent.  

I have a list of subsonic ammo that are no goes for the MCX 6.75, therefore avoid them in the 5.5; however, some of the goto subs sometimes produce a failure to lock back.  Its not a big deal, and may be contributed to powder/load discrepancies with that particular round or box of ammo.  

In conclusion, it doesn't eat all subsonics and that is where the issue lies and what I mean about my issues, which appear to be similar with yours as you've figured out what works as well.

@killerb6 - any updates?

I don't have a 6.75" Sig barrel, but there is a lot of good info here that has mirrored my experience with 300blk in AR platforms down to 6.5" and in the 9" LT.

I find that as the shooter, I can hardly tell a sound difference in an autoloader using 1680 vs. powders that are supposed to be "quieter".  But I can tell a BIG functional difference.  I've had no issues with sub reliability in any 300blk barrel I've used as long as it is 220gr bullets, with AA1680, using 300blk specific mags.  Change those variables, and reliability can drop.  I've used 208gr bullets as well with no issues, but would not go lighter than that if I wanted reliability in a short autoloader.  Especially changing the powder; I haven't tried them all, but I have not tried a powder other than 1680 that will run reliably (or at all) in an autoloader with subs.
Even reloading, shooting subs is pretty expensive, so I haven't shot thousands of them, but to date keeping the load as indicated above, I have not had any reliability issues in the 9" LT even on the "-" gas setting.  But switching to "+" for subs is probably not a bad idea.

If anyone gets any more specific data about the video it would be interesting, but right now it seems like anything related to the malfs in the video is pure speculation.

This thread is making me glad I decided to use a 9” barrel on my Gen 1 that I’m waiting on a Form 1 for.