MP5SD style upper for an AR15/M16

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  • ar15dave

    AR15Dave
    Jun 10, 2008
    2,194
    Monrovia, MD
    Well I am starting a new build. An HK MP5SD style upper for an AR15/M16. So far I have sorted out most of the parts except the barrel and a decent 7" handguard with an OD around 2".

    The plan is to be able to swap the suppressor on my HK MP5SD I have now with this upper when I want to.

    Parts So far:

    HK MP5SD rubber handguard
    stripped upper
    BUIS
    Dust cover

    Wish me luck and appreciate any input you may have.
     

    ar15dave

    AR15Dave
    Jun 10, 2008
    2,194
    Monrovia, MD
    so a short barrlel AR15 upper that will accept your MP5SD suppressor. Handguard could be tricky 2" ID is big, I am doing a build and I went here for 1.8" ID


    Maybe missread. I was stating the OD (Outside Diameter) would like to be around 2". The handguard cover from HK will be mounted to the 7" long handguard. The inside Diameter should be around 1.8" I think. I will measure my MP5SD OD
     

    smdub

    Active Member
    MDS Supporter
    Nov 14, 2012
    3,855
    MoCo
    Interesting build idea re-using the SD suppressor. Getting a barrel threaded & drilled to fit it I guess? A CMMG RDB 9mm bolt would be the cats meow for not getting as much gas in the face.
     

    SCARCQB

    Get Opp my rawn, Plick!
    Jun 25, 2008
    13,577
    Undisclosed location
    I took the easier route.
    Spikes tactical brown recluse integrally suppressed AR9.

    It has a ported barrel and an encapsulator to capture the vented gas into the can.

    It’s quieter than a factory MP5 SD
     

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    teratos

    My hair is amazing
    MDS Supporter
    Jan 22, 2009
    51,665
    Bel Air
    I took the easier route.
    Spikes tactical brown recluse integrally suppressed AR9.

    It has a ported barrel and an encapsulator to capture the vented gas into the can.

    It’s quieter than a factory MP5 SD
    Is there some kind of delayed blowback on those, or is it straight blowback?
     

    SCARCQB

    Get Opp my rawn, Plick!
    Jun 25, 2008
    13,577
    Undisclosed location
    It’s a straight blowback. But with a heavier bolt carrier and buffer spring.

    Since I modified it to use the Troy tomahawk pdw stock . I used a heavier spring yo compensate for the lighter buffer.

    Then upgraded to a hiperfire 9mm trigger.
     

    teratos

    My hair is amazing
    MDS Supporter
    Jan 22, 2009
    51,665
    Bel Air
    It’s a straight blowback. But with a heavier bolt carrier and buffer spring.

    Since I modified it to use the Troy tomahawk pdw stock . I used a heavier spring yo compensate for the lighter buffer.

    Then upgraded to a hiperfire 9mm trigger.
    Give the Scheel roller delayed system a try, if you are so inclined. It does a very nice job with a lighter bolt and spring. I put it on my Colt pattern SBR, and like it a lot.

     

    SCARCQB

    Get Opp my rawn, Plick!
    Jun 25, 2008
    13,577
    Undisclosed location
    Also, I’ve experimented with short barrels for an alternative to ported barrels.

    I found out that a 3” ar9 barrel will keep the 124grain FMJ subsonic without the need for complex porting. Some anemic 9mm ( 115 grain ) will also be subsonic. The suppressor’s back pressure also helps with reliability on the short barrels.
     

    wbw2123

    Member
    Nov 19, 2012
    839
    Interesting build idea re-using the SD suppressor. Getting a barrel threaded & drilled to fit it I guess? A CMMG RDB 9mm bolt would be the cats meow for not getting as much gas in the face.
    I sometimes find my mind wandering re SD supressor in other applications- sterling ala modern mk5 (actually planning to do this one), fbp, uzi, etc. I now this is added to that list.
     

    ar15dave

    AR15Dave
    Jun 10, 2008
    2,194
    Monrovia, MD
    Interesting build idea re-using the SD suppressor. Getting a barrel threaded & drilled to fit it I guess? A CMMG RDB 9mm bolt would be the cats meow for not getting as much gas in the face.
    Will have to give that a look. I am using a standard 9mm ramped bolt for now but will change items out as I get new ideas.

    The hardest part to get right now is the barrel. Cannot find anyone that has just the barrel. Ronin Arms makes a barrel/suppressor package but, won't sell the barrel separately.

    Anyone know where I can get an AR15 9mm ported barrel 5.75" long?
     

    inkd

    Active Member
    Aug 4, 2009
    6,973
    Ridge
    I took the easier route.
    Spikes tactical brown recluse integrally suppressed AR9.

    It has a ported barrel and an encapsulator to capture the vented gas into the can.

    It’s quieter than a factory MP5 SD
    I've looked for one of those for a while and cannot find them anywhere. Are they still making them?
     

    ar15dave

    AR15Dave
    Jun 10, 2008
    2,194
    Monrovia, MD
    OK, so I have a few of the parts in. Will be posting pictures and descriptions shortly. I am thinking of going with a 3" or 4" barrel with a 3-lug end on it for now until I can get a ported barrel that would work with my MP5SD can. The handguard is 7".

    Thoughts?
     

    outrider58

    Pronouns: It, That
    MDS Supporter
    Jul 29, 2014
    39,622
    OK, so I have a few of the parts in. Will be posting pictures and descriptions shortly. I am thinking of going with a 3" or 4" barrel with a 3-lug end on it for now until I can get a ported barrel that would work with my MP5SD can. The handguard is 7".

    Thoughts?
    Awaiting pics.
     

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