Gunsmithing Question - Mag Catch

[Boone97]

Well, I took some 320 sandpaper to the end of the spring, and between that and the filing I did on the side of the mag catch, I put 120 rounds through it at lunch today with no issues.

I have high hopes that the mag catch Dan Block is sending me will eliminate the problem.

[vanvock]

I'm in the same boat as Boone97 with a new TM1C (alum. frame). I've tried all of the above to no avail. Mine is not hanging up but I'm trying to get the catch knob to stay properly centered to possibly help jamming issues. Allowing it to ride the side of the frame hole doesn't seem to me to let the knob register correctly with the hole in the mag. I tried compressing the spring to shorten it & even cut a little off of the straight end that goes into the catch but no dice. The frame holes in mine are 3/8 & 5/32. I don't have to take the pivot plate out to clear the stop I just push it back some to get the catch out. The spring drops all the way in when off of the catch shaft. It is very tight to the shaft so that it needs prying to get off but looks like the pictures of new springs as far as coil spacing. Can someone give us an OAL of a working spring? I noticed that the catch lever was touching the frame @ the bottom with a gap where the shaft goes in like it wasn't square so I filed it down to get it even thinking that might be pushing it out but again no dice. No way to tell if the spring is fully seating when installed with pressure on it. What determines the stop point for the magazine? Is it the top of the channel on the back of the mag or the mag feed lips touching the receiver? I have 3 T11 mags that all have space to push up when inserted which seems to be mag holes to high or catch not high enough. I also cleaned up the casting ridges on the inside of the knob arm where it touches the frame to allow the knob to stick out a bit further. Though it's a semi this seems to be a universal area. Thanks for any help.

[reconbob]

I think I can now say for sure what causes the mag catch to lift out of the hole when you rotate the catch.

This is due to there being a nick or even just a curved worn spot on the top knife edge of the small hole where

it joins the big hole. The mag catch spring pushes against the upper edge, and down inside the hole the

leg of the spring is catching and hanging up instead of seating properly. So the spring is being compressed

in such a way that now the catch will lift when you rotate it.

The fix is to heavily file the knife edge with a swiss file to remove the nick or "dent" so there is a smooth

edge for the leg of the spring to slide along.

Since we starting using this fix we have been 100% successful in sloving the problem of the lifting catch.

All bets are off with an aluminum frame from a semi-auto, but for all other situations this should fix the

problem.

 

Bob

[vanvock]

Thanks Bob. The slot was pretty nasty & I think I got it cleaned up but I will re-visit to be sure. I didn't want to do too much all at once so there may be something of a ridge (knife edge) left in the slot where the 2 holes come together. It's now smooth & even but maybe I should eliminate it completely.

Edited January 1, 2018 by vanvock

[vanvock]

SOLVED: After re-inspecting the spring slot I found that while there was no nick or worn spot the top edge was tapered @ the bottom (right side) so as to form a slight ramp which was letting the spring push back. After more filing to level it out it no longer tries to back out. Little things mean a lot.

Thanks Bob for putting me back on the right trail.

Mike