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Making a custom upper for a MG

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I recently purchased a Mac 11 and was intrigued by the Lage uppers available for them.  I have been thinking about trying to make a customized upper and finally thought of a design that I believe could work.  Although, I am unsure about the legalities of proceeding to prototyping my design.  I know you can send your prototype to the FATD division of the ATF but that means I would have to make it first and I don't want to accidentally manufacture a machine gun.  Do you need to be a SOT?

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an individual can build anything for his own legal nfa weapon to enhance the existing design or change the caliber etc. the "CATCH" is the change cant be a machine gun and fire ALONE! or be made to do so by an "easy" alteration. one such animal was created by the tech people using a shoe string to make one run. you can complete your build then I would suggest you send it off for approval and make a prior agreement with some SOT to receive it should it not pass. they will not prosecute if a fault is found. in that case they would refuse to return it to you .

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I only accept postal money orders. contact me DIRECTLY before sending any funds                                           email  myoldiron@outlook.com        

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On 3/5/2020 at 4:49 AM, mike todd said:

an individual can build anything for his own legal nfa weapon to enhance the existing design or change the caliber etc. the "CATCH" is the change cant be a machine gun and fire ALONE! or be made to do so by an "easy" alteration. one such animal was created by the tech people using a shoe string to make one run. you can complete your build then I would suggest you send it off for approval and make a prior agreement with some SOT to receive it should it not pass. they will not prosecute if a fault is found. in that case they would refuse to return it to you .

So what about if you have a M11a1 and you have a catastrophic failure and a side blows out? Since you have to weld, is it ok to add two inches to the lower so that it would accept M11/9 uppers? Of course the cut and reweld will not affect the serial number or any identifying marks? What is the sensus? Sorta of like turning Stens into sterlings or so on. Thoughts? Ty

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Posted (edited)

see how fast things can change ? we went from a totally uncontrolled "UPPER" to a RECEIVER for a NFA weapon we would hope is in the registry. TWO COMPLETLY DIFFERENT ANSWERS I'M afraid.  addeing the length to the rec would change the model of the weapon from a M-11 to a M-11/9 and I DO NOT believe that would pass. it certainly would be ok to weld what ever it takes to repair the "catastrophic damage"  UNLESS ITS THE SIDE WITH THE SERIAL NUMBER !   if that was the case, I would send detailed pics of the damage AND the repair piece for PRIOR APPROVAL b-4 doing anything. no matter what is involved, because of the prior problems with the macs and those "DREAMERS" I would DOC every step with pics for your records.

Edited by mike todd
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I only accept postal money orders. contact me DIRECTLY before sending any funds                                           email  myoldiron@outlook.com        

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Thank you for all of the help.  My first couple designs failed but I recently came up with another idea that I believe could work better.  The idea is to make an adapter that allows a Mac m11a1 to attach to a PTR mp5 clone.  I attached an image of my idea below.  Please note that nothing is to scale and I am not an engineer.   MACMP5-BASCHI.jpg

I am thinking that starting with an existing trigger pack and modifying the sear arm to interface with the bolt would be the easiest way.  To my eye, it should not be able to be fired without the registered mac lower since the hammer would not have spring tension.  I am still trying to save up for a PTR so I am sure that the design will change once I can actually see what is going on inside of it.  Any thoughts?  I would hate to waste a lot of time and then figure out the ATF doesn't care for my design..

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I LOVE IT ! if nothing else it shows your desire and will to adapt.  wish I had your skills to get things on paper. all my life it was straight to the machine from my head and that created a ton of chips and failed parts . to the eye it looks like it should all do as planned 3 cheers for you


I only accept postal money orders. contact me DIRECTLY before sending any funds                                           email  myoldiron@outlook.com        

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Could you please get interested in conversions for Mk. II Stens?9_9

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if anyone ever makes a real magazine for the STEN, I might consider another one. I have owned 2, the first was a like new original WW II  Mk 2 the second, I made myself in .45 acp it used Grease mags and I regret selling it other wise note in my world.


I only accept postal money orders. contact me DIRECTLY before sending any funds                                           email  myoldiron@outlook.com        

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You can make a one-off design as long as it follows established criteria that FATD has already set in place. That is a bit onerous if you're new to that side of the industry.

Any more, to get a determination from the ATF, you have to send in the finished product assembled and in functional condition, in this case assembled and attached to your mac.

Then you wait a year or so for a determination.

But.....
Your design has a couple of things that the ATF has historically rejected. Look up the BRP MG34 upper and MG "legacy" conversions for more info.


You can't just drop an existing firearm on top of a mac lower nor can you introduce a new fire control group that is a mechanical deviation from what the manufacturer originally offered, i.e. open bolt to closed bolt by means of a new fire control group.

It's convoluted but that's how it goes.

 

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On 6/2/2020 at 7:48 AM, mike todd said:

if anyone ever makes a real magazine for the STEN, I might consider another one. I have owned 2, the first was a like new original WW II  Mk 2 the second, I made myself in .45 acp it used Grease mags and I regret selling it other wise note in my world.

Mike,

I don't mean to hijack the thread but...

I bought a number of aftermarket Sten mags from KeepShooting.com. They are very well made, the semi-gloss black finish looks a lot like the M1 carbine mags made in Korea.  I asked the company who made the mags for an article, but they would not tell me. Anyway, the mags work 99.9 % because the feed lips hold the 8-degree angle needed without distorting. 

https://www.smallarmsreview.com/display.article.cfm?idarticles=3018  

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Thank you for the information theredneckengineer.  That MG 34 conversion from BRP was very similar to what I was trying to do.  I guess its back to the drawing board.  

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FRANK, please feel free to "hi jack" any of my posts, you certainly dont need any ref's to make me bow or ceed the floor. actually i didnt go too deep with the sten issue on purpose , because i lack all the backup info.  I found some surplus mags with a polished and plated follower and the body exhibits a better mfg'ing process and they perform perfect in my LANCHESTER so i would assume work fine in the sten. BRP had them at the creek and i bought all he had at the time


I only accept postal money orders. contact me DIRECTLY before sending any funds                                           email  myoldiron@outlook.com        

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Some ideas work better than others. I have a M-11 with a Calico upper and certainly no way will the upper with the 50 rnd drum fire alone. Good luck with your project.

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the problem with the MP5 idea is that the MP5 "upper" is considered the receiver. so you would be making a new machinegun. Only way to do that is with a registered sear, cant use another machinegun receiver

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