‘Machine Gun Mike’ Explains The Operation Of The MP5SD

It has been awhile since we’ve shown the MP5SD any love. So, in case you missed our piece on the TP5SD from TPM Outifitters, who makes one of the best semiautomatic MP5SD variants on the market, here’s a nine-minute video from Machine Gun Mike on YouTube. In this basic but well thought out video, Mike explains the unique characteristics of the MP5SD submachine gun that allow it to shoot any type of  9 millimeter ammunition very quietly.

Besides being blessed with a suppressor that is nearly a foot long and two inches in diameter, the SD uses a reflex-type design where the suppressor mounts close to the chamber, rather than on the end of the muzzle. This allows the barrel to be ported with a series of holes within the first two inches of barrel. As the bullet travels down the barrel, gases bleed off into the suppressor from the ports, keeping the bullet’s velocity below the approximately 1150 feet per second speed of sound. As we have discussed at length in the past, the key to shooting truly quiet suppressed weapons is subsonic ammunition.

Instead of requiring specialized ammo, the MP5SD reduces the velocity of virtually all commercial rounds, making it one of the most quiet submachine guns ever designed.


LE – Science – OSINT.
On a mission to make all of my guns as quiet as possible.
Twitter: @gunboxready
Instagram: @tfb_pete


  • Henrik Bergdahl

    Almost as innovative as the integrally suppressed Sterling 😉

  • Major Tom

    This is all well and good but can he tell us why kids love Cinnamon Toast Crunch?

    • TheNotoriousIUD

      Because kids are idiots.

      • felix

        Actually it’s the taste. and you can see it.

      • Peter Balzer

        Idiot seems to be your favourite word…

        • TheNotoriousIUD

          It’s a useful descriptor.

  • Ευστάθιος Παλαιολόγος

    What happens if you “mistakenly” use subsonic ammo….?

    • It will still work; however, the projectile ends up at near .38 S&W velocities. Even so, the IWBA once promoted the use of 147gr subsonic ammunition through the MP5SD over any standard or +P loads with lighter weight projectiles.

      • Ευστάθιος Παλαιολόγος

        Thank you! I’d imagine they would get stuck in the barrel. Interesting

    • Ron

      You end up shooting a projectile at a very low velocity; there is a retelling of a LEO engagement with an SD and 147 grn rounds on the P&S podcasts and it is referred to as “giving him the bees” To summarize the one event as reported the fleeing armed suspect was swatting at what he thought were bee stings until he was stuck in the head. They later found several of the projectiles stuck in the man’s heavy coat.

      • Sunshine_Shooter

        Dang, beat me to it. Nice to see another P&S listener here.

  • TheNotoriousIUD

    The MP-5 is my first gun love.

    You never forget it.

  • Sermon 7.62

    Bad ergoes, no punch, but this kind of barrel and suppressor combination was a source of inspiration for VSS.

    • micmac80

      This is whole new level of hurt with 260gn low drag bullet,from a 9.3×39 round ,that maintains KE at much longer range than 9×19

  • thedonn007

    What does the MP5SD meter at with 115 grain 9mm?

    • Goosey

      Will be in the mid-800s or 900s.

  • One minor error in his explanation is that the bullet is never supersonic, the porting keeps the gas pressure low enough so it stays subsonic instead of taking a supersonic moving bullet and making subsonic.

  • Jim

    Always loved the MP5