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M-50 want fire constantly in full auto


wcwarren
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i recently purchased a 1943 M-50. The gun will not fire in full auto consistently. i talked to the previous owner and he said the gun work fine except the last time he shot it the magazine fell out because the magazine catch screw was too lose and he tightened it back up after cleaning the gun. i saw the old fourm and read a post a few years ago about a similar problem and it was mentioned about the mag catch screw being to tight want let the gun cycle due to the magazine being seated to tight. i loosen up the screw and the gun fire a magazine fine in full auto and then the next time the magazine fell out due to what i assume is the screw vibrating out. i then tightened the screw back up and it only fires semi auto in the full auto position. it seems like if it’s too tight it want fire full auto and if it lose the magazine screw it either drops out or it drops enough that causes the gun to jam. i have used the same magazines and using good new federal and Remington ammo. so, i don’t feel it’s a magazine or ammo problem. All of my magazines i have been using are HR 20&12 rounders. i am open to ideas if i am on the right track or do i need to check something else.

 

Also, while cleaning the gun i removed the bumper plug and the hammer spring and noticed what appeared to be a the remains of an old gasket in the spring any ideas on that. Just to add the gun shoots fine in semi the only jams i had was when the magazine was coming lose and dropping down.

 

William.

Edited by wcwarren
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You want that screw to be tight. The problem lies elsewhere. Use blue Loctite and tighten it in place.

 

These guns are famous for their lack of interchangeability. Some stuff just has to be fitted

 

I had a very similar problem with my 50. The gun ran 100% but the mag well wobbled due to the magazine guide pins not retaining it properly. I installed a new set of pins that were made to hold it securely against the bottom of the receiver and I found that most of my magazines still worked but a couple of them had the problem you are describing. The top of the feed lips were dragging on the underside of the bolt. In one case the gun would only single, in the other I could not even move the action bar to charge the chamber.

 

If ALL your magazines have this issue, simply grind or file the top face of the stud on the mag catch by a few thousandths till the mags fit. Be sure to maintain the radius on top of the stud as you go. Mag catches are way cheaper than magazines, so if your problem occurs with all your magazines, modify the catch. If you screw it up replacements are out there.

 

Since my problem was only with some mags I chose to modify only those mags which gave a problem. I took my Dremel and using one of the very small diameter stones made for sharpening a chainsaw blade, I took a few thousandths off the top of the catch hole in the magazine. I cannot overemphasize what a very small amount of material I had to remove. The difference is barely visible.

 

Procedure :

REMOVE THE FIRING PIN from the gun.

Take the retracting spring out of the gun and re-assemble.

Depending on whether you're modifying the mags or the mag catch, grind as required and trial fit.

When the action bar and bolt move back and forth freely with the empty magazine in place, confirm that you have removed the firing pin, load the magazine completely, reinstall the retracting spring and cycle the gun by hand.

If it feeds the whole magazine you’re done with the bench work, re-install the firing pin take it to the range and run a mag dump.

 

If you have modified the mag catch, you're probably done but it won't hurt to repeat the above test with each of them.

If you have modified the magazine, repeat for your other mags. It would not be a good idea to rework all your mags until you have gotten one to work.

 

Obviously YMMV

 

Wait for someone more knowledgeable than me to jump in, there may be other solutions

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Stranger Ranger,

 

This is a post on the forum from emmagee 1917 in 2012 that describes the same thing you are. Would you agree?

 

A mag fitting loose works, tight mags don’t. I'd think that the mag catch is setting a little high, holding the "good" mags too high up, allowing the lips to drag on the bolt, slowing it up, which slows the action bar, just when the springs are at their weakest, and just when the speed is needed to trip the hammer. It could also stop the bolt from locking up and allowing the hammer to fall around the pin rather than on it, but the hammer is not freed till the very end of the lockup, so that may be impossible.
Like the semi-Thompsons, you may need to get a spare mag release and file on it or try a different mag housing.


Another thought.....the looseness may allow the mag to move and self-correct a minor feed alignment problem between the mags and the feed ramp, removing some binding/friction.

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Yes, pretty much what I said.

The decision is whether you modify the mag catch of the mags.

If the problem exist with all your mags, then modify the catch

If it exists with some of your mags then you have a decision to make. Mags are expensive and irreplaceable, mag catches are cheap and replaceable (moreso if you'll accept a repop.) Whichever you choose just go slowly and fit it as you go

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