UZI Talk Forums
+ Reply to Thread
Results 1 to 12 of 12

Thread: Can a Open Bolt Upper for a Mac 11 work on a semi auto Mac 11 Lower

  1. #1
    UZI Talk Life Member

    Join Date
    Aug 2018
    Posts
    379

    Can a Open Bolt Upper for a Mac 11 work on a semi auto Mac 11 Lower

    Help settle this difference of opinion. Have someone wanting my open bolt upper for his semi lower
    ..I cant see how it can work since the semi auto lower has no way of
    cocking it when the bolt is retracted.


    And if there is a way, wouldnt it be illegal since open bolt semis have
    been not legal since the mid 80's ?
    Last edited by Haris1; 06-21-2022 at 08:03 PM. Reason: typo
    Any One Who Thinks The Pen is Mightier Than The Sword
    Obviously Never Encountered Automatic Weapons
    General Douglas MacArthur

  2. #2
    UZI Talk Life Member
    theduke's Avatar
    Join Date
    Mar 2012
    Location
    OreGun
    Posts
    696
    Swap the fireing pin.

    Open bolt FP is fixed
    Semi FP is slotted.


    No clue on CB semi....don't own one
    Or I missed the point......wouldn't be the first time.

  3. #3
    UZI Talk Life Member
    Hey...'s Avatar
    Join Date
    Apr 2016
    Location
    Atlanta
    Posts
    3,133
    I’m going on the premise you’re referring to the 380 when you say Mac11...

    The open bolt upper itself will work just fine on a semi but the (open) bolt has a fixed firing pin machined into the breech face and will have a full-mag runaway when you release the bolt forward trying to chamber a round on the closed bolt M12.

    If you’re referring to an M11/9. The only difference is the semi has a slotted firing pin compared to fixed on the open bolt MG. The upper on a factory MG has slightly different slots on the bottom for clearance but that has zero effect dropping it onto a semi-lower. Just swap the firing pin to a semi version. That’s only for the M11/9, not the 380.

  4. #4
    UZI Talk Life Member

    Join Date
    Aug 2018
    Posts
    379
    i am referring to a M119mm not the 11a1
    so how will the open bolt upper work on the semi m11 lower
    will it cock when you retract the bolt?
    Any One Who Thinks The Pen is Mightier Than The Sword
    Obviously Never Encountered Automatic Weapons
    General Douglas MacArthur

  5. #5
    UZI Talk Life Member
    Hey...'s Avatar
    Join Date
    Apr 2016
    Location
    Atlanta
    Posts
    3,133
    Now that we know it’s an M11/9 we can see the only real difference is the firing pin.

    You have a full auto gun so you can see the difference between your firing pin and this semi-auto slotted version.

    Semi-auto (from internet, Practical Solutions)


    Full auto pin (my garage floor)


    The (semi) slotted firing pin pictured lets the pin stay recessed until the semi hammer smacks it to drive forward.

    If you put a full auto firing pin (no slot/fixed) into a semi-auto closed bolt gun, the bolt will move forward trying to chamber a round but instead of having the slot letting the pin stay recessed, it will act like a machinegun firing every round in the magazine regardless if the trigger is pulled. Can be very dangerous, and if done intentionally, illegal.

    If you sell the upper or bolt, don’t include a full auto firing pin unless the guy has a tax stamp to stay good.

  6. #6
    UZI Talk Life Member

    Join Date
    Jul 2015
    Location
    DFW
    Posts
    1,051
    To answer the original question, will an open bolt upper work on a semi lower. Yes. If you are asking if the SMG bolt will work in a semi lower, then you have a problem. As stated you have to change the firing pin in the SMG bolt for it to work properly. If you friend things he can convert his semi closed bolt to semi open bolt by using your upper then Houston we have a problem. First off it wont work and second it would be illegal in the US. No idea about other jurisdictions.

  7. #7
    UZI Talk Life Member

    Join Date
    Aug 2018
    Posts
    379
    Quote Originally Posted by nklf View Post
    To answer the original question, will an open bolt upper work on a semi lower. Yes. If you are asking if the SMG bolt will work in a semi lower, then you have a problem. As stated you have to change the firing pin in the SMG bolt for it to work properly. If you friend things he can convert his semi closed bolt to semi open bolt by using your upper then Houston we have a problem. First off it wont work and second it would be illegal in the US. No idea about other jurisdictions.
    he doesnt want open bolt . I sent him a lage upper with an open bolt. i dont think he can swap out the bolt,correct?
    Any One Who Thinks The Pen is Mightier Than The Sword
    Obviously Never Encountered Automatic Weapons
    General Douglas MacArthur

  8. #8
    UZI Talk Life Member
    Hey...'s Avatar
    Join Date
    Apr 2016
    Location
    Atlanta
    Posts
    3,133
    Quote Originally Posted by Haris1 View Post
    he doesnt want open bolt . I sent him a lage upper with an open bolt. i dont think he can swap out the bolt,correct?
    Finally we get to the real question.

    The Lage Max11 & Max31 bolts have a fixed firing pin machined into the bolt face. Won’t work in a semi M11/9.

  9. #9
    UZI Talk Life Member

    Join Date
    Aug 2018
    Posts
    379
    Ok, here is the magic question
    The buyer wants to buy a semi M!! and use the upper which came off my open bolt M11
    Can he swap the bolt from the closed bolt semi into the Lage Mark1 upper?
    Thanks
    Any One Who Thinks The Pen is Mightier Than The Sword
    Obviously Never Encountered Automatic Weapons
    General Douglas MacArthur

  10. #10
    UZI Talk Life Member

    Join Date
    Apr 2007
    Location
    Louisana
    Posts
    1,791
    That would be a question for Lage to answer.

  11. #11
    UZI Talk Life Member
    theduke's Avatar
    Join Date
    Mar 2012
    Location
    OreGun
    Posts
    696
    I'd guess bolt is a different length....You don't specify Fuk all.

    Its blind mans bluff.....starting to stank.

  12. #12
    UZI Talk Life Member
    m11stuff@hotmail.com's Avatar
    Join Date
    Nov 2004
    Posts
    2,058
    Quote Originally Posted by Haris1 View Post
    Ok, here is the magic question
    The buyer wants to buy a semi M!! and use the upper which came off my open bolt M11
    Can he swap the bolt from the closed bolt semi into the Lage Mark1 upper?
    Thanks

    As someone else stated before, installing an upper with a machined fixed firing pin on a semi lower will cause a runaway machine gun after releasing the bolt on the first round. It won’t just chamber a round, it will fire until empty regardless of if you are pulling the trigger or even holding the gun. Additionally, it is “Contructive Possesion” of a machine gun.
    Richard Lage
    Lage Manufacturing, L.L.C.
    www.max-11.com

+ Reply to Thread

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts


Please consider becoming an UZI Talk Supporter.