Inside the MP5SD

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  • chase45

    Plinker
    Rating - 0%
    0   0   0
    Nov 6, 2019
    23
    3
    Evansville
    New guy here. Figured I would show you guys something a bit fun for my first thread. This is much less of a how to and more of a friendly discussion on the gun as well as introducing myself a bit.

    The MP5SD was this unicorn of a gun growing up to me. One that I had only seen in pictures and was very unique. The unique thing it does in case you are not familiar is it takes standard 9mm ball ammunition down to subsonic velocities to prevent a supersonic crack that you can experience with lighter 115 and 124 grain loadings. It accomplishes this by several ports just forward of the chamber which then bleed out into a large expansion chamber in the suppressor. Coupled with a large 12" reflexing suppressor it is quite the quiet gun.

    Here is a box full of parts needed to make a MP5SD. I used a LSC flat, RCM BCG and trunion, a Swiss B&T barrel, and a TPM suppressor

    TlLdhE7h.jpg


    Flat is bent and barrel is headspaced in the trunion

    P2E3zCVh.jpg


    Checking fit
    qWuOXvMh.jpg


    fFYJu0Yh.jpg


    Then the magic gets put into them
    isHiSd7h.jpg


    iMwTSk0h.jpg

    Then I refinished it in the nicest epoxy paint Lowes had to offer. I then worked up a solution using modified Mlock rails to mount some goodies to it. The one bad thing about the SD is the lack options to be able to mount accessories.

    [SUB][SUP]
    p6aUdbxh.jpg


    [/SUP][/SUB]
    UeJwZjdh.jpg



    Video of it getting built up and another of it getting some use

    <span style="font-family: Verdana"><span style="font-family: Verdana">[video=youtube;CYWZdlBXqMo]https://www.youtube.com/watch?v=CYWZdlBXqMo[/video]

    <span style="font-family: Verdana"><span style="font-family: Verdana">[video=youtube;wXHTU1WDF08]https://www.youtube.com/watch?v=wXHTU1WDF08[/video]

    Let me know what you guys think!

    Sorry for the long winded post with a ton of pics but I hope you guys enjoy.

     
    Last edited:

    rosejm

    Master
    Rating - 100%
    11   0   0
    Nov 28, 2013
    1,775
    129
    NWI
    Pay attention folks, THIS is a quality 2nd post.


    That's some sweet looking hardware there.
    Can ya' build me one of those?
     

    Beowulf

    Master
    Site Supporter
    Rating - 100%
    66   0   0
    Mar 21, 2012
    2,880
    83
    Brownsburg
    Nice! Looking good. I kind of regret letting my SD go, but I couldn't justify keeping it after I sold my sear, when I already had tri-lug adapter for my Hybrid to go on my MP5.
     

    chase45

    Plinker
    Rating - 0%
    0   0   0
    Nov 6, 2019
    23
    3
    Evansville
    Pay attention folks, THIS is a quality 2nd post.


    That's some sweet looking hardware there.
    Can ya' build me one of those?

    Thanks!

    Perhaps down the road. Ive been looking into getting a FFL a little bit. I would love to go full SOT. But I dont think I could ever justify the expense for the few I would make a year for people.

    We will see how it goes. With a gunsmith FFL I could still offer atleast some services. But to really build them from flats for people I would need SOT status.

    For now I just enjoy doing a build here and there. This was my most recent but I have also done a HK53 clone in 300 blackout as well as building a MP5 from a kit and a few other odds and ins builds such as a RPD and CETME L. Ive got a MP34 kit stuck back for when I really figure out how to build guns
     

    chase45

    Plinker
    Rating - 0%
    0   0   0
    Nov 6, 2019
    23
    3
    Evansville
    Nice! Looking good. I kind of regret letting my SD go, but I couldn't justify keeping it after I sold my sear, when I already had tri-lug adapter for my Hybrid to go on my MP5.

    Cant blame you there. I wish I had a sear.

    The SD is probably my favorite of the triology. Im not sure if its the weight, drop in velocity or simply the big can, but it shoots very gently. But it certainly takes more maintenece and much more cleaning than a normal MP5 and a 3 lug can. I will say the SD is noticeably more quiet than my K or regular MP5 suppressed with subs; but it is not leaps and bounds more quiet.
     

    Hop

    Grandmaster
    Site Supporter
    Rating - 100%
    16   0   0
    Jan 21, 2008
    5,084
    83
    Indy
    Fantastic!

    My HK holly grail gun would be a suppressed HK53 in 300BLK. I've thought about building one myself using a flat.
     

    chase45

    Plinker
    Rating - 0%
    0   0   0
    Nov 6, 2019
    23
    3
    Evansville
    Fantastic!

    My HK holly grail gun would be a suppressed HK53 in 300BLK. I've thought about building one myself using a flat.

    Im probably going to rebuild mine next. It was my first HK build, and it shows it.

    It is a cool caliber. However its not very quiet in my experience. I get a ton of port pop with subs. Surprisingly the supers were much quieter than I expected. I think this is mainly due to the bolt operating at higher speeds and not allowing it to be open as long.

    Ive ordered some parts to play with trying to delay the opening a bit. Ive got a few tricks up my sleeve to try and get it to lock longer. But I think part of me expects it to be as quiet as my MP5 guns suppressed, and Im not sure that it will ever be. However it certainly sails subs flatter and more accurate than the MP5 will.

    Here she is though
    [FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]
    6fZhJL4h.jpg
    [/FONT]
     

    chase45

    Plinker
    Rating - 0%
    0   0   0
    Nov 6, 2019
    23
    3
    Evansville
    Dude that's awesome got any vids of the 300 blk?

    Heres the build video and testing with some subs. They are not quite the quality of the SD video. I got better over time and more proper equipment(namely a tig welder) to build rollerlocks

    [video=youtube;lT1drKg-qNY]https://www.youtube.com/watch?v=lT1drKg-qNY[/video]

    [video=youtube;t59Zm1FaMRE]https://www.youtube.com/watch?v=t59Zm1FaMRE[/video]
     
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