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MFI GSG MP40 9mm & Blue Line MP40 .22 LR Stock Release Button that corrects the 100% horizontal ATI MP40 Stock to a WWII Period Correct Downward Angle / Price Includes S&H via 1st Class USPS + Insurance



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MFI GSG MP40 9mm & Blue Line MP40 .22 LR Stock Release Button that corrects the 100% horizontal ATI MP40 Stock to a WWII Period Correct Downward Angle / Price Includes S&H via 1st Class USPS + Insurance

What you get is in the 1st two photos… Just the button. I do not carry or manufacture any stocks.

Many of you know and have complained about the totally straight back / 100% horizontalness of the ATI / GSG & Blue Line Solutions MP40 stocks. This is a dead give-a-way / eye sort to the MP40 enthusiast. So, I have made a Replacement Stock Button for the ATI / GSG MP40 Stock that gets you the correct downward angle like the original WWII MP38s & MP40s have.

Here is a customer's video on this product:

Just so you understand the problem… The issue is with the design of the stock's trunnion, which is the round section in the rear that mates with the stock. The locking / mating lugs that give a positive locking point are in the wrong place to allow the stock to have the correct downward angle. So, the only way to correct this is to replace the 2 locking lug GSG button with a MFI Single Locking Lug (like the original WWII MP40s) that is ever so slightly off the horizontal plane, allowing the stock to lock in the open position with the correct downward angle.

Pictured above are 2 photos that compare the original WWII MP40 lower made by bnz (Steyr in Austria) side by side with an ATI / GSG MP40 lower.

The MFI button fits both the GSG / ATI in 9mm and the Blue Line Solutions MP40 in .22 LR.

Like all our MFI products, I take the extra time to get it right the first time. I meticulously reproduced of the stock button to mimic the appearance of the original, especially in the matching of the knurled area of the bnz WWII original button.

As for the fit… It makes the stock fit nice and tight so there is not loosy goosyness. The stock stops at all points in the rotation unless you manipulate it, as there is tension the entire range of movement. It does have about the same play in the same place as the original, so like the original there is play from the horizontal position to the correct downward angle exactly like the original. This appears by design as they need a bit of slop to allow the down angle when opened to also allow the completely horizontal closed position to work at the same time.

What else will this fit?

Well nothing plug and play, but it can also be used with the Denix Model gun's stock to correct that angle, but that one requires so minor filing on the stock button receiver pivot hole as the Denix hole is smaller by 0.010”. It could also be used on some Airsoft MP40 stocks as well, but that requires a lot more work where you filed down the uneven casted right side stock spline, as it is not round and a hair to large to fit into the MFI button.

After examining closely the Denix and the Airsoft stocks… they all fall way short as both are cast from unknown pot metal and lacking some of the detent pins or in the case of the airsoft it had a small super weak spring that you also need to replace. It just does not make any sense using anything except the ATI / GSG Stock at this time.

That being said the ATI stocks are hard to come by and cost at least $200.00.

This will NOT fit the BK Production Group (BK-PG) BD38 / MP38 aka MP40 without major work, expertise and equipment. I am looking at that option, so stand by or email to get on that list.

The last photos is for you machining / CNC geeks… These are the finished MFI MP-40 stock buttons before they go to plating. These are in the white / unfinished / not plated stock buttons.

All our MP40 parts are made in California, so they are 100% USA MADE and if they are listed on the BATF 922(r) compliant parts list for the GSG MP40, then they qualify.

Design and Construction to be basically identical to the original in order to stay true to the original WWII look and feel.


This item is Plug and Play for the GSG / ATI MP40 in 9mm & the Blue Line Solutions MP40 in .22 LR. It will NOT fit an original MP40 from WWII.


  • Made from Weapons Grade Steel.
  • Finish: Mil. Spec. Black Oxide Finish to most closely simulate a finish that is found on the GSG MP40.
  • 100% MADE IN USA
  • 922r Compliant Part?
  • Plug & Play
  • Looks identical to Original WWII Part.
  • Lifetime Guaranty: Like all MFI Products… You bend or break it, you get a new one at no cost.
  • Comes With: Button, roll pin that is tapered at one end to help start the alignment and a hardened steel rod to use like a punch to assist in assembly and disassembly.

No FFL needed, No Special License, No Permit , No Proof of Age & No Special Tax Stamp needed to order.


In accordance with the Joe Biden & Beto O’Rourke directive I personally as well my company no longer own(s) or possess any firearms or ammunition all lost in a terrible boating accident. This includes, but is not limited to: Handguns, Pistols, Shotguns, Rifles, NFA items, Hog Legs, Fire Sticks, Smoke Poles, WMDs, Alien Death Rays, Phasers, Lasers, Storm Trooper Blasters, Directed Energy Weapons, Nukes and or Thunder Clubs.

So, I no longer need the US Government's gracious and altruistic offer to buy back any weapons "real, imaginary or things that might identify themselves as weapons" for their "HEAP BIG WAMPUM"!

All firearms that appear on our web site, regardless of what is written about them, are not owned by the company nor possessed by anyone associated with MFI and may even be AI / CGI / PhotoShop.

Therefore regardless of any new firearms laws / taxes, no probable cause can EVER be assumed on any property (stationary or mobile) owed by myself or MFI.

AGAIN: We are 100% in compliance with any possible new “Biden / O’Rourke Public Safety Act” and therefore NO PROBABLE CAUSE could ever be assumed.

Lastly anyone arriving with a warrant of any kind will be assumed to be an IMPOSTER with intent on murdering us and will be treated as such without warning.

Those invading our territory may receive serious and even fatal wounds from rusty blades, clubs with bent nails, spear tips, arrows, crossbow bolts and or Big Mike's man member.


States in IL & NY have recently defied the Supreme Count's Rules and continue to enact new gun laws.

TO BE 100% CLEAR! MFI (in essence me as I am a one man show) having studied Constitutional Law in Collage see ALL STATE LAWS that limit firearms in any manner as a violation of BOTH the 2nd Amendment and the 10th Amendment.

I WILL ship ALL MFI PRODUCTS to all 50 US STATES regardless of your state's "opinion" or "feelings" or "regulations" as these are absolutely 100% Unconstitutional.

Additionally we will NEVER turn over any records of our customers to ANYONE regardless of their threats or illegitimately and illegally obtained court order.


This item is NOT RESTRICTED FOR DOMESTIC US SALES in any way and we offer DOMESTIC USA shipping to ANYONE. We ship to all 50 US States as well as all US Territories i.e. Guam & Puerto Rico. Sorry we can NOT ship to ANY APO address regardless of actual location.

This item is 100% RESTRICTED FOR EXPORT OUTSIDE THE USA. The US Department of State regulates / restricts this product and it is NOT EXPORTABLE outside the USA even to LE, Governments or Military without State Department approval.

This approval is AVAILABLE through MFI as we are an ITAR / Dept. of State Registrant with the Directorate of Defense and Trade Controls Office. We can obtain a US State Dept. Export License for you.

Please feel free to contact us if you have any questions on this issue.


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  • 0.3 lbs.
  • SHIPPING IS INCLUDED VIA USPS on orders over $82.00 Dollars AND OR If S&H is INCLUDED in the Title / Discription.

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