I SBRed a Colt SMG-pattern DDLES AR15 lower about a decade ago. I haven't shot it much lately, since I have another CMMG RDB Glock-mag AR15 PCC which I use for USPSA that gets most of my PCC shooting time. But in my quest to put folding stocks on all the things, I started looking around last year to see what options there were for uppers that allowed a folding stock on a Colt SMG-pattern lower. In short, there really wasn't anything. The Angstadt MDP-9 and the Matador Arms Montgo-9 both have BCGs that cycle completely inside the upper receiver and so allow folding stocks, but they only work with Glock-mag lowers. However at SHOT 2023, Matador Arms announced a newer design, the MAT-9. It's advertised as working with pretty much any single- or double-stack 9mm AR15 magazine system, so I pre-ordered one at the end of January and it was finally delivered a couple weeks ago.
For the folding stock, I used a KNS picatinny stock adapter with SIG telescoping/folding stock. The top rail on the upper is maybe a 1/4" higher than a normal AR15 upper, so it's not really noticable when shooting. The handguard has MLOK slots on the bottom and sides. I found the small diameter of the handguard caused my hand to rub up against the charging handle, so I installed a Magpul MVG foregrip to allow me to grip the gun a little lower. The handguard is integral to the upper receiver, so unfortunately there's no chance of swapping it out for something else a little larger.
The upper is blowback operated. The carrier is just one solid piece with a hole drilled in the back for the recoil spring, and a dovetail which the bolt fits into. The bolt isn't very much more complicated, it's square and has hole for the firing pin and extractor and that's it. The 8" barrel doesn't appear to be user-swappable. The recoil spring, buffer and endcap are held in with a little C-clip at the rear of the endcap that you have to push down to release everything. It all just doesn't just pop free once the upper is separated from the lower.
The charging handle is swappable from to either side, and doesn't reciprocate. I didn't particularly care for the charging handle design. The diameter was too small for me to comfortably grip, but that could be resolved in the future if a larger diameter replacement charging handle was designed. The other problem is that since I'm used to the AR15 manual of arms I kept grabbing at the back of the receiver where the charging handle isn't. Due to how the upper works though it'd require a fair amount of redesign to move the charging handle to the normal location. One thing I can't forgive though is the fact that even though the charging handle is in the same location as on an MP5, there's no notch to lock the bolt open (and then HK-slap it closed). My Metalform Colt-pattern mags wouldn't load on a closed bolt unless there were less than 10 rounds in the magazine.
At the same time I got the upper, I also got an ECCO Machine adapter to convert my Gemtech Mk9K silencer from the factory 3-lug mount to a 1.375"x24 Bravo pattern threading. This was also part of the reason for getting a new upper. My old upper had an integral 3-lug machined into the muzzle, so if I changed the Mk9K from a 3-lug mount to something else, at a minimum I'd have had to change the barrel on the old upper. The MAT-9 barrel is threaded 1/2x28 so I stuck a Griffin Armament Plan-A taper mount on it. There's still a little bit of shift now when I remove the silencer, but not nearly as much as before with the 3-lug mount.
For just less than $600 delivered, I'm mostly happy with it. I can live with my complaints. With the likely(?) demise of non-NFA braced pistols I have to wonder how much the market for SBR-length uppers is going to drop though, so I wonder if Matador is going to bother developing this further, or maybe make a 16" version?
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Originally Posted by The Rat
