Angstadt Arms MDP-9: MP5 Meets AR15

Angstadt Arms has recently released their MDP-9 carbine, an AR-type lower coupled with a roller-delayed blowback upper assembly. This is the same operating system as the much-lauded MP5, and Angstadt version of the design is remarkably light, handy, and simple. It is made specifically for Glock magazines, and is available in pistol and SBR configurations (the one in today’s video is an SBR). With a just-under-6″ barrel and side folding stock, it makes for a very compact package. I really like the weight, size, and simplicity, but I wish it came with a better trigger and ambidextrous safety. There are technically better magazines out there, but I do understand that the Glock wins on the basis of ubiquity.

Have a look at how the MDP-9 works today, and then stick around for tomorrow’s video, where I will take it out to the range to compare on the clock against an H&K SP-5!


  1. You’re not really going to see gas piston operated 9mm carbines because the cartridge just doesn’t generate enough gas

    MPX has entered the chat.

    • I see where you’re coming from, but I consider it an update (with a better understanding of the mass-balance) of the Thompson Autorifle or Villar-Perosa. All (including roller delay) ultimately depend on the same principles.

    • My understanding is that ANY work done by the bolt takes energy, and the energy left over is recoil. Which might be absorbed and redirected by the return spring. The sharpest recoil often comes from the bolt striking the back of the receiver.

  2. At around 2 minutes Ian makes a comment regarding blowback weapon operation and rifles, which means nothing unless you specify the cartridge that you’re talking about – and he did not do so.

    This might be confusing for newbies.

    I’ve got blowback rifles. They are variously 9 mm and 45 ACP… The stemple / BRP automatic weapon.

    • The statement you’re referencing is right after he says a 9mm carbine has no trouble functioning just great as a simple blowback, and right before he explains that simple blowbacks (even in 9mm) tend to have more recoil, and why.

  3. The energy and momentum that would have gone into the bolt hitting the end of the receiver

    Is still transferred to the firer, via the delay system

    It’s not as though the recoil has been spread out over a longer time period, as a pure blowback with a long bolt travel and a good buffer system, like a Sterling would do.

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