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Thread: Mp40 / Mp41 compatibility - anyone?

  1. #1
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    Default Mp40 / Mp41 compatibility - anyone?

    Does anyone have experience with, or know if a lower receiver from an mp40 will swap out with an mp41 lower / stock?

    Im talking complete lower witg fcg, stock etc.

    My understanding is that mp41 is an mp40 with a modified mp28 stock and lower?

  2. #2
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    Yes, I built an MP-41 parts kit into a conversion for my MP-40. I can swap back and forth in about three minutes if I don't bother with changing the barrel to look more "MP-41-ish". (Scott Andrey made me the barrel.)

    The only modification to the (Wilson tube- not original) receiver was a "porthole" in the underside to accommodate the semi-auto disconnector in the MP-41 parts set.
    Last edited by DINK556; 06-27-2012 at 06:21 AM. Reason: spelling

  3. #3
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    So the erb mp41 should have the disconnecter relief already...
    Awesome.
    What did you do about the barrel profile, and front sight housing?

    And thanks by the way

  4. #4
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    Doesn't look very compatable to me.......

    MP-41 receiver remnants/trigger group


  5. #5
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    Quote Originally Posted by Borsig View Post
    So the erb mp41 should have the disconnecter relief already...
    Awesome.
    What did you do about the barrel profile, and front sight housing?

    And thanks by the way
    You're welcome.

    As far as the barrel profile and front sight stuff is concerned, I did it the easy way and sent the MP-41 barrel assembly to Scott Andrey and told him to make me an MP-40 barrel and barrel nut that looked like the MP-41 barrel assembly as much as possible. He did so and used the parts from the MP-41 front sight to complete it. I did have to send it back to him once for a minor adjustment, but it was taken care of with his usual superb service.

    The "pseudo-MP-41" barrel assembly wouldn't fool any of the knowledgeable MG nuts on this board, but at a quick glance it looks enough like an original to satisfy me.

    I went from an MP-40 to an MP-41. If you're talking about going the other way and converting an MP-41 to an MP-40, it shouldn't be a problem as long as the hole for the locking piece (take-down pin?) is present in the underside of the receiver. It's not needed for the MP-41, but it's probably there anyway since most of those tubes were built into MP-40s anyway. Swapping the barrel out would require another custom-made barrel since the barrel attachment methods are totally different, but I bet you could have Scott or someone make you a barrel that attaches like an MP-41 barrel, but looks externally like an MP-40 barrel. Then you just need the special long socket to turn the nut on and off and you're all set.

    Obviously there will be minor fitting issues, but it should work.

    And villafuego- it helps if you close one eye and hold the parts kit at arms length, then self-administer a little Jack Daniels. Once the creative juices start flowing, you would be amazed what starts to look compatible.

  6. #6
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    Dec 1969
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    Quote Originally Posted by DINK556 View Post
    You're welcome.

    As far as the barrel profile and front sight stuff is concerned, I did it the easy way and sent the MP-41 barrel assembly to Scott Andrey and told him to make me an MP-40 barrel and barrel nut that looked like the MP-41 barrel assembly as much as possible. He did so and used the parts from the MP-41 front sight to complete it. I did have to send it back to him once for a minor adjustment, but it was taken care of with his usual superb service.

    The "pseudo-MP-41" barrel assembly wouldn't fool any of the knowledgeable MG nuts on this board, but at a quick glance it looks enough like an original to satisfy me.

    I went from an MP-40 to an MP-41. If you're talking about going the other way and converting an MP-41 to an MP-40, it shouldn't be a problem as long as the hole for the locking piece (take-down pin?) is present in the underside of the receiver. It's not needed for the MP-41, but it's probably there anyway since most of those tubes were built into MP-40s anyway. Swapping the barrel out would require another custom-made barrel since the barrel attachment methods are totally different, but I bet you could have Scott or someone make you a barrel that attaches like an MP-41 barrel, but looks externally like an MP-40 barrel. Then you just need the special long socket to turn the nut on and off and you're all set.

    Obviously there will be minor fitting issues, but it should work.

    And villafuego- it helps if you close one eye and hold the parts kit at arms length, then self-administer a little Jack Daniels. Once the creative juices start flowing, you would be amazed what starts to look compatible.
    I currently own a 1940 122 code MP-40, and have handled enough MP-41's and parts to wonder how you swap back and forth (in about 3 minutes).... how do you retain the MP-40 tube on the MP-41 stock unless it has permanent mods that would not allow replacement onto an MP-40 lower?

    The MP-41 trigger group is permanently affixed (welded) to the bottom of the tube, and the receiver is only retained in the stock by 2 screws that attach to permanently affixed (welded to the receiver)mounts

    I'm just curious......

  7. #7
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    OK, I don't have the time to put together a detailed "how-to" right now, but the short version is that you add filler sections between the various parts of the trigger group and other pieces that live in the stock to make them one solid assembly. You add a "tongue" to the front of this that will engage the slot under the front of the MP-40 receiver that holds it when it's mounted on the normal lower receiver. You then carefully remove the remains of the old receiver.

    Install the MP-41 end cap on the MP-40 receiver and position it on the new "unitized" MP-41 lower receiver parts so it sits nice and tight on the lower receiver parts. You then weld the end cap to the tang that sticks out at the back end of the MP-41 receiver parts, then cut that tang loose from the rest of the assembly. Install the MP-41 lower receiver parts in the MP-41 stock, drilling a new hole and using a wood screw to hold the back end in place.

    When everything is done, you will be able to install the MP-41 end cap (with attached tang) on the MP-40 receiver in the normal twisting way, then catch the "tongue" sticking out of the front of the MP-41 stock under the front of the MP-40 receiver and pivot the whole assembly down onto the MP-41. (Think of putting an M1 Garand receiver into the stock. The method is the same.) You then use the rear action screw (and it's little locking screw) to anchor the tang that you welded to the end cap and your "sorta" MP-41 is ready to shoot.

    See- it's the Jack Daniels that actually does it. ;^)

  8. #8
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    Oh hell, now Im defintely confused

    So if the trigger group housing is welded to the tube - no so easy as it would seem then.

    Better find out before making the move on buying this MP41.....

  9. #9
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    Quote Originally Posted by DINK556 View Post
    OK, I don't have the time to put together a detailed "how-to" right now, but the short version is that you add filler sections between the various parts of the trigger group and other pieces that live in the stock to make them one solid assembly. You add a "tongue" to the front of this that will engage the slot under the front of the MP-40 receiver that holds it when it's mounted on the normal lower receiver. You then carefully remove the remains of the old receiver.

    Install the MP-41 end cap on the MP-40 receiver and position it on the new "unitized" MP-41 lower receiver parts so it sits nice and tight on the lower receiver parts. You then weld the end cap to the tang that sticks out at the back end of the MP-41 receiver parts, then cut that tang loose from the rest of the assembly. Install the MP-41 lower receiver parts in the MP-41 stock, drilling a new hole and using a wood screw to hold the back end in place.

    When everything is done, you will be able to install the MP-41 end cap (with attached tang) on the MP-40 receiver in the normal twisting way, then catch the "tongue" sticking out of the front of the MP-41 stock under the front of the MP-40 receiver and pivot the whole assembly down onto the MP-41. (Think of putting an M1 Garand receiver into the stock. The method is the same.) You then use the rear action screw (and it's little locking screw) to anchor the tang that you welded to the end cap and your "sorta" MP-41 is ready to shoot.

    See- it's the Jack Daniels that actually does it. ;^)
    I decided to have some Knob Creek on the rocks while reading your description, and now see it......the parts normally permanently attached to a MP-41 tube were modified to remain permanently attached to the MP-41 stock, and basically function as the tray (with integral endcap) that's in an MP-40 lower the tube twists/locks in to....

    clever!......no permanent mods to an MP-40 receiver.......I'd advise the OP against modding an original MP-41 receiver to fit an MP-40 lower however....

  10. #10
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    The gun Im thinking of, is an Erb MP41 I am looking into buying. Not an original. I have no idea how charlie erb built it. Ive asked that question of the seller , however

  11. #11
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    Knob Creek works, too!!!

    Yeah, it all depends on how the MP-41 mentioned in the original post was built. If it matches the original method of construction, then the trigger group parts will be welded to the tube and it would be a bitch to remove them without really damaging something. Starting out with an MP-41 parts kit made it easy, as the receiver tube is already trashed. I would check to see how the Erb tube gun was built up before I thought about trying for a convertible MP40/41. The MP-41 is still neat a gun, though. Not seen too much and no worries about stock wobbles like the MP-40 is prone to. You even get semi-auto if you want it.

  12. #12
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    right - but..... Its not exactly correct for a Wehrmacht reenactor though....

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