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MP40 Mag Catch "fix" (New Catch)

Posted: Fri Jul 15, 2011 7:33 pm
by No1_sonuk
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:
mp40_magrls_1.jpg
:D

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:
mp40_magrls_2.jpg


It's a direct replacement for the existing catch.
mp40_magrls_4.jpg

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...

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Fri Jul 22, 2011 2:25 pm
by Broadsword
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 !

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Sat Jul 23, 2011 1:35 pm
by No1_sonuk
:good:
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.

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Mon Jul 25, 2011 7:40 am
by greedo1980
Well worth it when you consider the cost and inconvenience of having to replace lost magazines.

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Mon Jul 25, 2011 8:21 am
by Cadaceus
No1_sonuk wrote:
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

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Mon Jul 25, 2011 9:01 am
by No1_sonuk
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.
  • 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.
  • Push out the old mag catch.

Fitting
  • Insert the new mag catch in its place on the side of the receiver.
  • Now is the tricky part: You need to get the washer onto the screw, inside the release button.
    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).
  • Drop the spring onto the button.
  • Turn the receiver assembly so that the button hole is facing down, and insert the button up into the hole.
  • Hold the mag catch into the side of the receiver and do up the screw.

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Mon Jul 25, 2011 4:19 pm
by Cadaceus
pm sent

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Tue Jul 26, 2011 7:02 am
by Broadsword
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.

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Thu Jul 28, 2011 1:28 pm
by Cadaceus
received mine today with thanks

Cad

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Thu Jul 28, 2011 1:33 pm
by Cadaceus
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

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Thu Jul 28, 2011 1:42 pm
by No1_sonuk
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.

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Thu Jul 28, 2011 1:52 pm
by Cadaceus
Can't see it being a huge problem but ta anyway

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Sat Oct 22, 2011 3:23 pm
by Broadsword
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.

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Sun Oct 23, 2011 5:52 pm
by cdfw
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..

Re: MP40 Mag Catch "fix" (New Catch)

Posted: Mon Jan 23, 2012 4:27 pm
by ukace1960
Hi do you have any more of the catches , as I need one.
cheers Steve