1928A1 Feed Issues

[MG08]

So I have a USGI 1928A1 here for cleaning/repair and consignment sale. Owner had issues with feeding from magazines ( drum seems to work ok) - it would appear that the magazine catch is riding to high in the trigger frame since the magazines do not latch well, and are dragging on the bolt. the lower is not matching to the upper, which could be the issue. So first question - does anyone have a GI mag catch for sale ? Alternative is to file down the existing one a little - are these hardened ?

[reconbob]

If it's a G.I. Gun, with correct original trigger frame and mag catch,

I would first suspect the magazines. I do not understand what you mean

when you say the mags are dragging on the bolt since no part of the

mag touches the bolt. Should you determine that the catch itself needs

to be dressed so that it will snap into the hole in the rib of the mag, the

catch is not hardened and can be filed.

 

Bob

[jim c 351]

Using Crosby mags???

That could be the problem.

Jim C

[MG08]

Thanks for the info and thoughts.. NO crosby - a mix of different USGI ones. It really acts like it is being slowed as it drags across the top of the magazines - perhaps not riding on the mag lips bur on the ammo - and hard to get the mags to latch in. You will et one shot, then live round under the closed bolt, then a 3 shot burst, then live one under the closed bolt.... the magazines work fine in my guns. My guess is tolerance stacking and the mag catch is just a hair to high when all is said and done. the Drum ( original) is fine- but it latches differently and is spaced by the upper receiver . I don't have any spare catches or complete lowers. I may try a lower off one of my guns too. Just to see if there is an effect.... Keep up the good ideas.

[imageaudio]

Why don't you take the magazine catch off your gun and install in the malfunctioning gun and see if that resolves the issue? I always try to swap parts to isolate the problem before I begin removing metal from anything.

 

APEX has mag catches in stock and for sale for $40.

https://www.apexgunparts.com/thompson-magazine-catch-w-spring-g.html

[reconbob]

Aha. If you are getting a live round under the closed bolt it is because

the bolt has recoiled far enough to eject the fired case, but not far enough

to pick up the next round. This is short recoil. It could be the ammo, it could

be a shot out barrel, it could be you are are too light on the trigger and the sear

is dragging on the bolt slowing it down.

 

Bob

[jim c 351]

MG08,

You say you are getting a live rd under a closed bolt??

Is the primer getting hit?? How hard ?? Is the bolt completely closed ?? Of the cartridges that fire, how hard is the primer hit??

Does this stoppage only take place when fed from the right side of mag?? The left side of mag??

Jim C

[MG08]

Some good questions - When I say "under" I am referring to the fact that the rounds chamber but do not fire. No consistent side - L or R feed from the magazine. Light primer strikes, he light strike ammo will fire when run through a second time. I will get some more trouble shooting in and see if I can isolate the problem

[deerslayer]

If you depress the follower and stick something in a side hole so it stays down then you can install the magazine and operate the bolt by hand to see if you have drag between the feed lips (bent up) and the bolt.