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Benelli M3 Super 90 HK import - M4 C Stock project


johnlewjohn
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I have searched High and Low looking for information on adding the Benelli M4 C Stock to the M3 and found one pic.

 

So here goes my project.

I want to add the M4 C stock to my M3 HK import with the full length tube.

 

I am in need of some info though.

 

Primarily, does anyone know what the threads are on the M4 Receiver extension?

The existing threaded hole on the HK import M3 is smaller than the M4 tube.

 

I have two options, the fixed M1014 tube or I also could go the M4 3-pos route. The only thing I need is the nut, and I can order that from Numrich.

 

(cause I know someone will bring it up)

As far as 922 issues it appears that M1 and M3 and M4 internals are all the same.

The Geissele M4 hammer is identical to the M3.

I would assume that the FFT trigger/hammer/disconnect are alike also.

I imagine the followers are the same as well.

Can anyone verify this or has anyone tried swapping their M3 parts for these?

Edited by johnlewjohn
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That build is definitely eye-catching...I like the curves, and how does it function?

 

SD, the pitch is 1.0 but does anybody know by what? 15?

I will have to ream/drill and re-tap the threads but I will need to determine that as well right?

Knowing Benelli it is probably something proprietary like 18.2x1.0

 

Thanks

 

John

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M21 x 1 - 6g

M19 x 1 - 6g

 

Yeah, drill and tap for any adequate gunsmith. If you really want to make the modification correctly you would take it to a machinist to have the hole enlarged with a boring bar, then thread it with a threading endmill. Depending on if you are going to leave the aluminium raw or coat it again; you would then calculate your pitch diameter.

 

There is alot of leverage in that area with very little threads to hang on too, do it correctly or face a bent-out-of-shape receiver.

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Vertigo,

 

to clarify:

 

M21x1-6g is the new thread size including the M4 receiver extension?

M19x1-6g is the size currently on my HK M3?

 

Thanks

 

John

 

Yeah that is correct. at the end the "6g" means medium class of fit and external threads. You could technically have your gunsmith run the threads at a tighter fit to hold better, but the issue will be finding a tap in that size.

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00Storm,

 

What can you tell me about the flashlight rail and the front barrel clamp.

Are those custom or available from somewhere?

 

Thanks

 

John

 

The front barrel clamp came with a surecycle magazine extension.

http://www.brownells.com/shotgun-parts/magazine-tube-parts/magazine-tube-extensions/shotgun-magazine-tube-extension-kit-prod23213.aspx

 

The flashlight rail is a GG&G for an 870 that I ground with dremel to fit. I increased the diameter for the magazine tube and ground the top to fit the square barrel junction. It fits solid with no movement.

http://www.gggaz.com/remington-870-sling-and-flashlight-combo-mount.html

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I have a email for a gunsmith who will re thread the extension and not the receiver if that's what you are looking for ? He has done this for several m3 owners .

 

i also have the 5 position m3 adjustment tube and lock nut , it will need to be thread to fit the older m3/hk receiver.

 

Here is the info below

 

Village Gunsmith & Police Supply

200 West Main Street,

Morristown, TN 37814

423-839-2088

Ivan Helton

[email protected]

Edited by heckler&kochp2000
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I have a email for a gunsmith who will re thread the extension and not the receiver if that's what you are looking for ? He has done this for several m3 owners .

 

i also have the 5 position m3 adjustment tube and lock nut , it will need to be thread to fit the older m3/hk receiver.

 

I had thought about going with that option, however, I need the threads intact on the extension to install the M4 C stock.

 

I already have the extension and I just ordered the nut to make it work.

I really want to thread the receiver.

 

Thanks

 

John

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To thread the receiver is more risky than threading the extension. The threads have noting to do with the collapsing part on the stock. But correct me please if i have misunderstood you. It will be a lot cheaper if something where to go wrong. Also he only threads partially the portion need to mount on to the receiver, and leaves enough threads for the pistol grip to screw on.

Edited by heckler&kochp2000
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To thread the receiver is more risky than threading the extension. The threads have noting to do with the collapsing part on the stock. But correct me please if i have misunderstood you. It will be a lot cheaper if something where to go wrong. Also he only threads partially the portion need to mount on to the receiver, and leaves enough threads for the pistol grip to screw on.

 

No you're right, I wasn't concerned about the stock, but the pistol grip has to screw on to those threads.

Weren't you concerned about the integrity of the extension though?

So there is a step on the threads? 19mm for engaging the receiver, and then steps up to 21mm?

Still has room to time the extension, install the nut and pistol grip, and feel solid?

Does anyone have a picture of this from their project?

Now you have my attention.

 

Would be very hard to fix a blotched receiver..........

That is something I am keenly aware of, I cant even remember the last time I saw an HK import with a factory full length tube.

That is definitely weighing into the equation.

 

Thanks

 

John

Edited by johnlewjohn
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I laughed when I saw the picture cause I did the exact same thing to my M3 dummy tube and have the same marks on mine to boot.

That's awesome...not sure what a 166S is but I believe that would be very similar to the M4 3 -pos I have.

 

FWIW, I did try reaching out to Ivan with no luck, but I was pretty busy today.

I will try again tomorrow.

Edited by johnlewjohn
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(166s) is the part number for the 5 position adjustment tube for the Benelli supernova/m3 collapsible stock.But the end threads that screw into the receiver are thes same on the (166s) and the Benelli M4 recoil tube for the pistol grip to screw on. But the 3 position recoil tube for the Benelli M4 will only work with the Benelli M4 collapsible stock and the 166s will only work with the supernova/m3 collapsible stock.

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  • 4 weeks later...
  • 4 weeks later...
  • 7 months later...

So now that I converted my M3 Super 90, I have one more shotgun that has been gaining traction in the thought processes of my mind about modifying that butt stock as well... I was thinking of doing the same thing to my HK imported SBE.

Anyone out there ever try modifying one of those?

I believe that the same thing should be possible as it uses the same style extension, just need to do the thread reduction and should be good to go... Thoughts?

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  • 3 years later...

I am trying to find definitive answers to adapting a SN tube and stock to my M3. In the thread I found you had a pic of  what you did to your tube but the link is broke and I can’t see the picture.

Could you help out please??

 

Thank you,

Tom

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