There was a thread on this forum a while ago about problems with the AGM MP40's mag catch not gripping properly.
At the time, I had a quick look at the problem and saw that there was only a small amount of protrusion of the catch pawl into the mag well, and that this could be causing the problem some people are having.
While looking for a solution, I had the catch out, and thought it might be possible to make a whole new catch, but with a deeper pawl.
Well, it is: 
Further examination showed that the length of the pin determines how far the release button is pushed out, and hence how far it can move. Increasing the pawl depth might adversely affect the release.
So when I added 1mm to the pawl depth, I added 1 mm to the pin length too:
It's a direct replacement for the existing catch.
It sticks out a bit more either side than the original, but it's not really noticeable.
I made 2 (in aluminium) and I don't have the problem with my MP40 yet...
Just fitted one of the prototypes to my faulty MP40 and it works like a dream.
The catch was filing to engage properly with the mag before because the lug did not protrude far enough into the mag housing. This mod works perfectly.
Thank you - I now have a skirmish capable gun rather than just a cool looking prop !
Let me know if there's anything that needs changing.
Something I forgot to mention is the angle on the catch pawl. I've used 45 degrees instead of the much shallower angle on the original.
This might make it a bit harder to insert a magazine, but it has 2 advantages:
1) It's easier to make like that because I can use a 45 degree angle milling cutter, rather than a complicated angled jig.
2) It gives a wider "land" on the top of the pawl, meaning it'll take longer to wear to the point it causes problems.
The 2 prototypes have been sold to members here. If anyone else wants one, I'll make more to order - PM me.
Price would be £25 inc postage for painted black or bare aluminium.
Well worth it when you consider the cost and inconvenience of having to replace lost magazines.
AGM MP40 - AGM STG44 - CYMA Thompson M1A1 - WE P08 4 inch - Marushin M1 Carbine GBB - AGM Sten MkII
The 2 prototypes have been sold to members here. If anyone else wants one, I'll make more to order - PM me.
Price would be £15 inc postage for painted black or bare aluminium.
Very interested in one of these but how easy are they to install for a noon like me?
Is a guide available?
Cad
Impressions:
U.S. 35th Inf Tech Sargeant
British Royal Artillery Gunner
Generic SS Mann
Weapons:
Cyma M1A1
ASG Sten MK2
ASG MP40
TM M1911A1
WE Browning High Power
HFC Mauser C96
I could do a picture or video guide, but it's quite simple if you can operate a screwdriver.
I found it easier to do this with the upper receiver removed from the rest of the gun, but it can be done without doing that.
Removal
- Carefully undo the screw in the centre of the release button.[/*:m:3imtn5re]
- When it reaches the end of the thread, the spring will push the button out, so be careful not to lose the screw or the tiny washer when it does. Unscrewing with the button facing down reduces the chance of losing the washer.[/*:m:3imtn5re]
- Push out the old mag catch.[/*:m:3imtn5re][/list:u:3imtn5re]
- Insert the new mag catch in its place on the side of the receiver.[/*:m:3imtn5re]
- Now is the tricky part: You need to get the washer onto the screw, inside the release button.
- Drop the spring onto the button.[/*:m:3imtn5re]
- Turn the receiver assembly so that the button hole is facing down, and insert the button up into the hole.[/*:m:3imtn5re]
- Hold the mag catch into the side of the receiver and do up the screw.[/*:m:3imtn5re][/list:u:3imtn5re]
Fitting
I do this by holding the button with the open end up and dropping the washer into the button, then pushing the screw up through it (holding the screw on the screwdriver).[/*:m:3imtn5re]
pm sent
Impressions:
U.S. 35th Inf Tech Sargeant
British Royal Artillery Gunner
Generic SS Mann
Weapons:
Cyma M1A1
ASG Sten MK2
ASG MP40
TM M1911A1
WE Browning High Power
HFC Mauser C96
They are incredibly simple to fit. If you can change a light bulb you can fit this part !
I'm off skirmishing next weekend so I'll give you a reliability update. But it seems fine just testing it out at home.
received mine today with thanks
Cad
Impressions:
U.S. 35th Inf Tech Sargeant
British Royal Artillery Gunner
Generic SS Mann
Weapons:
Cyma M1A1
ASG Sten MK2
ASG MP40
TM M1911A1
WE Browning High Power
HFC Mauser C96
update:
fitted mine in about 30secs, really easy
mags now feel secure,
have to ram Kings arms 110 round in a bit harder but well worth it
Thankyou Sir
Cad
Impressions:
U.S. 35th Inf Tech Sargeant
British Royal Artillery Gunner
Generic SS Mann
Weapons:
Cyma M1A1
ASG Sten MK2
ASG MP40
TM M1911A1
WE Browning High Power
HFC Mauser C96
Glad to hear it.
If the ramming is a problem, filing the catch edge should be easy enough as it's aluminium.
I'll post an image of what I mean later.
Can't see it being a huge problem but ta anyway
Impressions:
U.S. 35th Inf Tech Sargeant
British Royal Artillery Gunner
Generic SS Mann
Weapons:
Cyma M1A1
ASG Sten MK2
ASG MP40
TM M1911A1
WE Browning High Power
HFC Mauser C96
This has just reminded me that I never did post back. After a day of skirmishing the catch worked brilliantly - an excellent fix so thanks.
Just fitted mine this afternoon along with a new alloy muzzle nut and retaining spring.. Great mod and so easy to fit..
Along with Dadio's 'receiver twist' fix I'm so much happier with my MP40..
Thanks again Tim..
'Non adepto demens. Adepto etiam'
War does not show who is right, only who is left..
Hi do you have any more of the catches , as I need one.
cheers Steve
I make them to order if I don't already have some. I've just had a query by PM, and as the temperature's a bit more tolerable in the garage, I'm about to make some more.
Hi, I realise this is an old thread but do you have any spare MP40 mag release mechanisms left. Mine broke in half last weekend and I need a replacement ASAP for December game in Kettering . Thanks in advance
Hi, I realise this is an old thread but do you have any spare MP40 mag release mechanisms left. Mine broke in half last weekend and I need a replacement ASAP for December game in Kettering . Thanks in advance
I'll see what I can do over the weekend. PM me if you've not heard by Monday evening.
Brilliant, thank you.
Hi, really not sure the pm thing is working on here. Yes please, paint it black. Thank you for sorting this , what do I owe you and what is your PayPal. Appreciate your assistance. Is it easy to fit.
