Angstadt Arms MDP-9
Angstadt Arms MDP-9 (Image courtesy JWT for
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The H&K MP5 has been an icon for over half a century. And for the last 20 years of that, we’ve been hearing about how some new firearm that comes along will be The MP5 Killer, the one to finally wrest away the MP5’s sub-gun supremacy. That hasn’t happened yet.

The Angstadt Arms MDP-9 won’t be the “MP5 Killer.” But it should be.

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Hailing from Charlotte, North Carolina, Angstadt Arms has been in business for a little under a decade. The 10 gunsmiths who make up the business set to building what very few companies have accomplished; a high-quality roller-delayed blowback action with all the modern ergonomics and options shooters expect.

There are a lot of semi-auto and full-auto sub-guns on the market, but relatively few roller-delayed options. The reason is obvious. A simple direct-blowback action is easy and cheap to manufacture and good enough for most folks.

A roller-delayed-blowback action is significantly more complex. That complexity translates directly to expense, and relatively few people are willing to shell out the money unless they are a serious competitor or the money being spent is the government’s dime.

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There is, however, a real benefit to the roller-delayed blowback action, and the faster that bolt is cycling, the more significant that benefit gets.

For the more common direct-blowback system, the rearward force of the bolt is slowed only by the mass of the bolt itself and a spring (or springs). A roller-delayed blowback system has one or more rollers that must be overcome prior to the bolt moving rearward.

This delay allows for pressure to drop and provides a noticeably smoother recoil cycle. For full-auto submachine guns, that keeps the muzzle down and allows for a very controllable firearm, even with guns that have a fairly high cyclic rate.

That smooth action and spread-out recoil impulse is exponentially more valuable if the gun doesn’t have a stock. With a roller-delayed blowback action, the shooter is much more likely to be able to control muzzle rise and get the pistol’s muzzle back on target quickly.

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How well does it work? The above photo is the result of 15 rounds fired in 15 seconds, at 50 yards. That was with an Aimpoint Patrol Rifle Optic mounted, shooting standing, suppressed, without a stock or brace of any kind and without a sling. If your goal is to hit a 19″ silhouette at 25 yards, the speed of your trigger finger is the limiting factor, not recoil management.

The MDP-9 does a great job doing exactly what a roller-delayed blowback action was designed to do, and somehow it does it with much less mass to the bolt than most other actions of this type. The entire pistol weighs only 3.7 lbs, about a pound lighter than most of its competition (an MP5 pistol chambered in .22LR weighs almost 6 lbs.).

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Take a look at the bolt head in the photo above. It’s about 70% the size of a similar MP5 bolt head, maybe less. The whole action is that way. I’m still scratching my head trying to figure out how they’ve managed to shrink the size and mass of the action parts — and the entire gun — and still keep recoil so light and smooth.

The whole point of the MDP-9 is to create a modern roller-delayed sub-gun. A big part of that modernity is easy user customization.

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The MDP-9 uses a standard(ish) pistol caliber carbine trigger and fire control group. It ships with a basic “mil-spec” two stage trigger. It breaks like any of them, too heavy (at 6 lbs 5oz) and with plenty of squish. But if you’d like to upgrade, it’s easy enough to do, as the MDP-9 will fit several different aftermarket PCC triggers.

The same goes for the grip. It ships with a perfectly adequate Type 23 P-Grip pistol grip from B5 Systems. This grip fits the format well, as it’s a bit more vertical than most AR style grips. However, should you want to change it as well, there’s several dozen other manufacturers of AR grips available.

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To the rear of the pistol you’ll find a standard M1913 Picatinny rail. You can do what you choose with it — a single-point sling attachment, a Black Collar Arms Adjustable Pistol Support, the brace of your choice, or you can SBR this thing using one of many stock options that are on the market.

The cascade of options continues on the upper receiver as well.

The handguard is integral to the receiver, so the length is fixed. However, you’ll find a few M-LOK compatible points around 270 degrees of the handguard.

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At the end of the barrel you’ll find morel options. The 5″ chrome moly barrel ends with a tri-lug flash suppressor and attachment. Unscrew that and you’ll find standard 1/2×28 RH threads. Options are nice.

So is familiarity.

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AR-15 type controls are found throughout the gun. The magazine release, although modified for the format, is right where it would be on your AR-15. So is the bolt latch and release paddle (no HK slap). The safety is a typical two-position AR safety and can be swapped out with the type of your choice, as long as it works with the trigger.

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The MDP-9 pistol takes GLOCK magazines, and ships with a pair of 27-round 9mm PMags. The mag well of the MDP-9 is well funneled, and magazine swaps are quick and easy. Each magazine I used, regardless of length or manufacturer, required a solid push for it to seat on a full magazine.

The bolt holds open on an empty magazine.

Pretty much the only thing that folks won’t be as familiar with is the charging handle. That’s simple enough, with a non-reciprocating charging handle that comes from the factory on the left side of the MDP-9, but can be easily moved to the right side if you like.

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For normal, decent right-handed folks, the non-reciprocating handle on the left side is just about perfect. With a “C-clamp” grip around the handguard, the charging handle makes a great front stop for your support hand, and really keeps the muzzle down and in line with the target.

Because of that, bump firing the MDP-9, even with the stock heavy-ish trigger, is easy to do when firing from the hip. Since the receiver includes a lower Picatinny rail, you could mount a laser or laser/light combo there, put the dot on the target, and blast away from the hip like the 80’s action star of your choice. I’m pretty sure that 73% of the time spent with these types of guns is spent exactly in this manner.

The full-length rail on the top provides plenty of real estate for mounting all sort of sights or optics, which is handy, as the MDP-9 ships without any sights at all. That was a disappointment.

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I put 500 rounds through the MDP-9 for this review. After a good spray of CLP, I put 60 rounds of mixed ammunition through the MDP-9 exactly as it shipped. After that, I removed the tri-lug muzzle device and attached an old AAC silencer.

The other 440 rounds of the review were all fired suppressed. I shot 115gr FMJs from a couple of brands. I also fired 124+P Speer Lawman rounds, 135gr Freedom Arms HPs, and a lot of Armscor 147gr FMJs. No round ever failed to fire or cycle. No magazine failed to drop or load.

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Considering how deep in the upper receiver the breech lays in relation to the ejection port, the fact that I had no reliability issues surprised me a bit. That long space is there because the bolt head has to come forward and backward to lock and unlock as the rollers retract.  That takes up some space. Despite a wide range of projectile shapes and weights, my reliability concerns were completely unfounded.

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Since the MDP-9 has a Pic rail at the back and a full-length rail on top, you’ve got an option with this gun few other sub-guns have to offer — a magnified optic and a mono-pod rear. I put the Black Collar Arms Adjustable Pistol Support on the back, a US Optics 10X scope on the top rail, and nestled the MDP-9 into a Caldwell Stinger Shooting Rest.

Using the Armscor 147gr FMJ ammo, I put 10 rounds into a 1.4″ group at 50 yards. This level of accuracy was easily accomplished with several different rounds.

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Moving to 25 yards and swapping the 10X scope for the Aimpoint PRO with its 2MOA red dot, that same 147gr Armscor round hit right at a 1″ five-round group when averaged over four shot strings. Every single round I tested through the MDP-9 at this range scored within 1/2″ on average of this round, showing that the limiting factor for precision is the optic and the shooter, not the gun itself.

In general, the MDP-9 has the same slick industrial look we’ve come to expect from roller-delayed blowback guns. HK set the standard a long-long time ago, and we’re used to it. If you don’t like the black Type III anodized hard coat finish, you can have the pistol Cerakoted FDE or “tactical grey.” As it is, the finish is extremely well done.

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There are a couple weird things on the gun. First is the fairly large square housing that juts off the left side of the gun for the spring-loaded ejector. I guess it has to be there, as the ejector needs some space to retract into every time the bolt comes forward.

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There’s also a series of large screws horizontally down the edge of the gun, holding the rails that the bolt slides on into the receiver. But also note those huge roll pins, and, for some unknown reason, they are all set in a little bit far to the left. I took a look at a few photos of other guns online, and they all seem to be this way. I have no idea why roll pins were used, or why they aren’t centered.

The MDP-9 is an extremely well-built gun. You’re going to need a punch of some type to remove the rear take-down pin, and the whole thing is put together well. There are no rough machining marks in the gun. Everything is smooth and well polished, with sharp lines where they should be and smoothed curves where they should be, too. I can’t find any part of the MDP-9 where the design wasn’t well thought out, or the execution of that design looks rushed or compromised.

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The end result is exactly what Angstadt Arms set out to deliver; a modern roller-delayed sub-gun that just happens to be lighter and with more complete options than anything else on the market. The Angstadt Arms MDP-9 is the new standard by which all others in its category should be judged.

Specifications: Angstadt Arms MDP-9

ACTION: Roller-delayed blowback
COLORS: Black Type III Hard Coat Anodized, Magpul FDE Cerakote & Tactical Grey Cerakote
MAGAZINE: Includes two (2) 27 round Magpul PMAG GL9 magazines.
ENDRAIL INTERFACE: 1913 endrail with QD sling socket.
UPPER ASSEMBLY: 7075-T6 aluminum monolithic upper receiver assembly with continuous top picatinny rail, M-LOK interface and QD sling points
CHARGING HANDLE: Non-reciprocating ambidextrous forward charging handle (can be swapped from left to right side)
LOWER RECEIVER: 7075-T6 billet aluminum lower receiver with flared magwell, extended magazine release, threaded bolt catch screw and B5 Systems Type 23 pistol grip
LRBHO: Last round bolt hold open on an empty magazine
FIRE CONTROLS: The MDP-9® is compatible with most aftermarket 9mm PCC triggers.
BARREL: 5.85″ chrome moly black melonite barrel with a 1/10 twist and threaded 1/2×28 TPI
MUZZLE DEVICE: Removable 3-lug muzzle device
WEIGHT (EMPTY): 3.7 lbs unloaded with no magazine
Price: $2,699

Ratings (out of five stars):

Style and Appearance * * * *
Industrial, as expected, but very well executed. The big, slightly off-center roll pins are weird, as is the giant ejector housing.

Customization * * * * * (+)
Swap triggers, grips, multiple slings attachments, M-LOK compatible rails, tri-lug or direct thread attachment, and then some. And yes, it takes GLOCK mags.

Reliability * * * * *

Accuracy * * * *
Nothing broke the 1″ mark, but lots danced around it. As it ships with no sights, precision is dependent on the optic you use and if you stick with the factory trigger.

Overall * * * * ½
I can’t think of a better performing roller-delayed sub-gun offered on the market. The Angstadt Arms MDP-9’s really got what everyone has been waiting for. Half a star off for not including a better trigger or any sights at this price point. If this gun were mine, it would be SBR’d already, and I’d still be shooting it. It’s a heck of a pistol.

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  1. “I’m still scratching my head trying to figure out how they’ve managed to shrink the size and mass of the action parts — and the entire gun — and still keep recoil so light and smooth.”


    less mass in moving parts + delayed blow back (Roller Delayed Blow back) > less ‘felt’ recoil

      • I quit performing at shoprite and currently I create $80h – $120h…how? I’m operating online! My work didn’t precisely make Maine happy thus i made a decision to require an opportunity on one thing new… when four years it had been so onerous to quit my day job however ;Zl’25} now I couldn’t be happier.
        Heres what I do………

    • The recoil is still there (although reduced), you just aren’t feeling it all at once. Its smoothed out to a logarithmic decay instead of a linear peak then decay.

      • I tried to think of a good example with something else you might be familiar with and that is…

        suppressors operate on the same principal except its a logarithmic decay of energy along the length of the suppressor and there aren’t any moving parts. In a sense of reduction… think of the less perceived sound you hear from a suppressor use as the less recoil you perceive from this firearm.

        basic high school physics.

  2. You’re the only person to have perfect reliability with that compared to dozens of ppl who don’t have reliability at all.

  3. All my AR-15s have Angstadt BCGs. Too bad they don’t make a .308 BCG. I settled on a Toolcraft .308 and the ejector pin was waaaaaay too stiff to depress. Removed the pin and the spring looked like it had been flared on each end. After tampering and polishing the spring, pin, etc. it feels the way it should. Nowadays it’s check, double check and triple check.

  4. I like the article and your input on this topic, but I do want to bring up one point you made about the DRB system, and it’s one I haven’t been able to find a good answer for as of yet.

    “A roller-delayed-blowback action is significantly more complex. That complexity translates directly to expense…”

    Is it really that much more complex and expensive to build? I have one myself, a G3, and I like it. But having read up on how it works and the origins of DRB, I have a hard time seeing why it’s significantly more expensive. To me it seems actually quite a simple system, more simple then an AR or AK style system. The rollers themselves while obviously requiring more machining then a heavy spring, don’t seem to be something that would cost an extra grand or two to produce. The DRB was designed by the Germans at the very end of WW2 in the STG45, with fast, mass production in mind. I’d appreciate your feedback on this topic.

    As a side note, I do really like that it has a bolt catch/release. It’s the only DRB firearm I’ve seen that has one and I’ve wondered why after all these years no one has included one in these types of firearms.

    • Thanks for asking such a smart and informed question.

      The receivers themselves of the old stamped metal designs are very simple, and quick to mass produce. There was certainly no need for a CNC to produce them.

      The bolt assembly is, however, more complex than something like an AR15 or an AK. Just to learn to do it, I’ve now made all of these style of bolt assemblies, for the AR, the AK, and the G3.

      But I should be careful on what I mean when I say “complex”. The cuts themselves on the bolt assembly aren’t particularly challenging, it’s not like your tool has to make some kind of awkward turns or super special tooling is required. There are simply more cuts to be made, or at least more passes from different positions.

      That means more fixtures, more tools, more times to start and stop the machines, and more times that you need to move the part (or tool) in the machine. Each stop and start adds to machine time, even if it’s machine down time. That’s very expensive, even in today’s modern CNC environment.

      For instance, with a good 13 axis swiss machine, a qualified shop can cut an AR15 bolt in about 8 minutes. There’s not much starting and stopping there. That’s just not the way it is for the roller-delayed bolts, at least not yet.

      When we take a look at the MDP-9, and especially the Stribog (which is super smart) we see that people are coming up with more elegant solutions to machine these parts, and I think we’ll see the prices drop accordingly.

  5. Is it safe to assume being roller-delayed will result in better suppressor performance, since the action remains locked for a moment longer than a direct blow-back action would?

    (And have you considered replacing the rusted bolts on your gun rest with stainless ones since it appears it lives a lonely life outdoors? 🙂 )

    • You would think, but I haven’t actually seen this occur.
      I’ve never met any blowback design, delayed or otherwise, that doesn’t need to run wet. The MP5 is famous for this. Note that I didn’t drop Lucas oil in this gun like I did with the Python in the previous review. I sprayed it with CLP. If you look closely, you can see the splatter on the receiver in the pics, because, like every blowback design, that stuff goes everywhere when the gun cycles.
      I’ve seen piston guns run cleaner suppressed, anyone can see the big difference that makes. But delayed blowback vs. simply blowback doesn’t really seem to make all that much difference, at least not that I can tell in the real world.
      Long story short, if you want a clean running gun with a can, any blowback action is not your friend, and if you want a blowback action to run well, lube the hell out of it.

      • “But delayed blowback vs. simply blowback doesn’t really seem to make all that much difference, at least not that I can tell in the real world.”

        I admit that kinda surprises me, as I was under the impression the delay before extraction would mean the barrel pressure would be substantially lower by the time the brass parts company with the barrel’s chamber. IE, the peak of the pressure impulse would be long gone by the time the gas seal between the brass and the chamber (the breach?) was broken.

        It’s always good when I get to learn something new in a day…

        • It is spread out over time, but the same amount of gas and junk is coming back.
          Take a look at the bolt assembly in the pics. Even after a wiped down for the pics it is filthy.

  6. All well and good but I built my AR9 for less than $700 and its accurate and reliable. No need to spend nearly $3k. I’m sure it’s cool but I’ve fired the MP5 and MP5K and well, I’m happy with my AR9.

  7. Have you fired a 9mm with CMMG’s radial delay? If so, how would you compare the recoil impulse with the radial vs roller delay?

    • I think CMMGs radial delay is just hype. I could tell no difference in the various 5.7s I have. I do like the Diamondback Blowback system. When you get the gas block adjusted to your ammo, that 3lb gun runs like a toy gun. Supper soft.

  8. I’ve been shooting delayed roller block actions since 1980. Owned at least one since 1982. Thousands of rounds. I mean tens of thousands. 9mm, 5.56, 7.62 NATO and 7.62X39. (Volmer conversion). Never a malfunction. Not one. Did you hear that? Not one. Never a parts breakage either. Put that in your AR and smoke it.

  9. Looks like a fun weapon for someone who’s got a big budget or someone paying for it. Definitely not I. That out of the way, this seems to eclipse the MP5 on a lot of levels. They just have to drive demand next. I suspect that means practically giving them away to Hollywood and I’d probably also do a bunch of shoots with video game producers as well.

    • “shoots with video game producers as well.”
      As far as I can tell, nothing sells guns better than this. Getting your gun in a popular FPS is gold.

  10. Ask the owners of this blog why they censor postings critical to those like this and others they are paid to write. At first I thought it was an anomole. Now I know its real. Yes my post was criticical of this weapon. And instantly its gone.

    • It’s important to understand the model of TTAG. The writers don’t get paid by the gun company, and we really are free to write whatever we want, and since I use adblock I don’t even know who the advertisers are. The gun companies themselves don’t pay TTAG for the reviews, at least they didn’t prior to the current ownership and I see no changes since they took over. TTAG gets paid primarily by the independent IP click. So the best way for TTAG to make money is on the comments. That’s what keeps people coming back over and over again.
      Since negative reviews get more clicks than positive ones, there is really an incentive to be overly negative, not overly positive. For every complaint that I’m too generous with a particular product, I get several complaints that I’m overly harsh. Maybe I am, but TTAG’s model rewards harsh reviews.
      Please try and repost your criticism. Honest debate actually makes this site money. It is not in their interest to censor posts, and I’ve never seen them engage in that effort.
      That said, all sorts of stuff gets hung up automatically from WordPress, my comments often do and I’m a longtime writer here. It’s pretty annoying.

  11. Did you have any issues with the bolt hold open working on your example? A popular gun historian tested one and had issues with LRBHO working sporadically at best, and not being tied to specific brands of magazines.

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