Gunsmithing Question - Mag Catch

[buzz]

Have you ever had a problem with the mag catch backing out of the hole and drifting to the left when you push on it?

 

When I push up on the catch, it walks slightly to the left, leaving about 1mm gap between the lower receiver and the mag catch.

 

This is enough to make the mag retainer on the mag catch to hang up on the hole in the trigger guard.

 

To get the mag catch to pop into place, I have to press the catch up against the lower with my thumb. Annnoying!

 

Any ideas? Out of spec mag catch?

[laurencen]

spring stretched

[ppgcowboy]

I changed a spring once and it did exactly what you describe. It is for certain the spring.

[buzz]

The spring stretched length wise?

 

What's the remedy?

 

Thanks

[ppgcowboy]

In my situation, when I pulled the mag catch, the spring for some reason did not seem to go all the way back in so it was wanting to push the mag catch back out. So I took it back out, buffed the end from any burrs and then put it back in, and it worked out fine. I did mangle the first spring I played with trying to get it in. I eventually bought a couple to sit in reserve just so I would not be in need of one in the future. I would throw a lot of oil in the hole and wiggle it around and see if it zeros itself out if that makes sense which is how I worked it out.

[laurencen]

coils should be tight, when it stretches and you assemble it you are compressing the spring coils, if its got any gaps in coils it tends to push the catch out of the hole, you could try putting some lube on the spring end before its inserted into the lower

[buzz]

Well, I got another catch and spring and tried to get it to work.

 

Every time I work the catch, it pops out sideways a couple of millimeters and jams.

 

Can't figure it out.

[1952HRA]

Do you have the pivot plate in when it does it because if the pivot plate is not in the gun the mag catch will work it's way out every time Edited May 6, 2017 by 1952HRA

[1952HRA]

If it works it's way out with the pivot plate in place I would try replacing the pivot plate because the notch on the front pin of the pivot plate is letting the mag catch open to far so that it catches up on the trigger frame

[gijive]

Buzz,

 

Are you making sure that the tip of the spring coil is engaging in the hole in the magazine catch?

 

 

 

[gijive]

If it works it's way out with the pivot plate in place I would try replacing the pivot plate because the notch on the front pin of the pivot plate is letting the mag catch open to far so that it catches up on the trigger frame

If the magazine catch is able to be removed with the pivot plate in the grip frame, the catch and spring aren't installed correctly. The pivot plate has to be removed from the gun to properly disassemble and remove the magazine catch.

[Adg105200]

Have you ever had a problem with the mag catch backing out of the hole and drifting to the left when you push on it?

 

When I push up on the catch, it walks slightly to the left, leaving about 1mm gap between the lower receiver and the mag catch.

 

This is enough to make the mag retainer on the mag catch to hang up on the hole in the trigger guard.

 

To get the mag catch to pop into place, I have to press the catch up against the lower with my thumb. Annnoying!

 

Any ideas? Out of spec mag catch?

Can you get any pictures of it with the gap?

 

Does this happen when the pivot plate installed?

 

Andrew

[1952HRA]

 

If it works it's way out with the pivot plate in place I would try replacing the pivot plate because the notch on the front pin of the pivot plate is letting the mag catch open to far so that it catches up on the trigger frame

If the magazine catch is able to be removed with the pivot plate in the grip frame, the catch and spring aren't installed correctly. The pivot plate has to be removed from the gun to properly disassemble and remove the magazine catch.

sorry if I didn't explain it clearly, I do know that a mag catch cannot be removed until the pivot plate is removed, but the pivot plate should not allow the knob that locks the mags in on the mag catch to come out fare anough to get caught up on the hole it means that the pivot plate is the problem not the spring or mag catch ( which Buzz said he has tried replacing already). And also on my trigger frame if the spring is not in the hole on the mag catch it doesn't push the mag catch to the left it just doesn't return the mag catch to it's position

[Adg105200]

Just a few reference pics. The catch shouldn't go much more than about halfway into the catch hole in the mag slot when the catch is depressed.

Edited May 6, 2017 by Adg105200

[reconbob]

The problem is when you are pressing the catch into final position -

from the left side to the right side the spring is being compressed so

when you rotate the catch and it clears the frame the compressed spring

lifts the catch. This caused by one of two things or a combination of both.

 

- the spring is too big in diameter and the outer diameter of the

spring is scraping on the hole. This is happening more because new

mfg. springs do not have the flat coil which prevents them from coming

off the catch and in general they are a little big.

 

- the recess for the mag catch is formed by drilling two holes. A big

hole with a little hole so close that it's supposed to break thru into the

big hole and this is the slot that the leg of the spring goes into to

provide tension. The small hole can drift away from the large hole at

the bottom - the drill is small diameter and flexible. When this happens

the holes are not connected all the way to the bottom and the leading

leg of the spring hits the burr and is compressed.

 

To check if it's the trigger frame and not the spring try the catch in

a different trigger frame. It it works it's the frame. If it still doesn't work

it's the spring or a combination of both.

 

If it's the frame you have to get all the way down into the slot formed

by the two holes with a small screw driver struck with a hammer or a

small triangular Swiss file or both. You have make clearance for the leg

of the spring to bottom out in the slot.

 

Bob

Edited May 7, 2017 by reconbob

[laurencen]

the spring has one end locate in the mag catch the other has a bend that should ride in the smaller hole Bob is referring, take a look and see if the bend is tight or has a radius inside of the bend, this can prevent the spring going fully down the hole and the spring acts like a compression spring than a torque spring and pushes the catch out of the hole when rotated,

 

also there may be a burr on this end, there is a difference between old original springs and new production

[buzz]

I got it to work properly. Thanks everyone for the advice.

I'll describe the fix just in case anyone else has this problem:

As Bob described above, the two holes in the trigger frame for the mag catch intersect and form a slot for the spur on the mag catch spring.

If the spring doesn't insert fully, it will compress and make the mag catch pop sideways when it is manipulated.

The spur on the mag catch spring rides along the TOP of the slot when the spring is compressed. So the top of the slot must be smooth, and the slot must be wide enough to allow the spring spur to pass along.

The slot on my M1A1 is wide and uniform all the way to the right side wall of the trigger frame.

However, as you can see in the Photo, the top of the slot had burrs and was uneven. The spur on the spring was stopping at the ridge indicated by the red arrow in the photo and not inserting fully.

Here's what I did:

1. I verified that the slot between the two holes is uniform and not malformed in any way, as described by Bob in the above post.

2. I inserted the spring into the hole without the mag catch and verified that it can actually bottom out against the right-hand wall of the trigger frame.

3. The small hole is 9/64" or close to it, so I took a 9/64" drill bit and VERY LIGHTLY twirled it in the hole with my fingers to see if there is any burr or fouling or corrosion in the hole that was hanging the spring up and keeping it from travelling all the way down the slot. The big hole is 1/2" or close to it, so I did the same with the big hole, twirled a 1/2" bit with my fingers to remove the line of burr on the top slot.

4. I took a very thin flat mill file and stuck it down the slot and gently smoothed the top of the slot just enough to remove the divot that was catching the spring spur. I had good luck with the mill file from the pictured kit, it's the perfect size and the serrations go all the way to the end of the file so you can smooth the slot all the way to the bottom at the far trigger frame wall.

The above was done very gently and removing the absolute minimum material. In fact, there was no real cutting done, the line of burr is still there, it's just smoother and uniform. The top of the slot is still uneven, but now it's smooth enough to pass the spring spur with out grabbing it. It's not anywhere near to "perfect" but it works 100%.

At this point the spring inserts fully and the mag catch works perfectly.

Edited May 7, 2017 by buzz

[shadycon]

Good work! I've always said " You have to know the problem before you can fix it"!

[buzz]

I don't know why, but I did not think to check the slot until I read Bob's post.

 

I assumed that since the catch worked previously, the slot must be good to go.

 

As soon as I looked at it for 10 seconds I saw the dent in the top of the slot that was grabbing the spring.

 

 

I changed out the springs in both my 28 Commercial and my M1A1 with NOS springs. I figured 70 years was long enough service life for a spring.

 

The original springs in the 28 were whipped, they were shortened (had taken a "set") and two even had light corrosion. The trigger pull went up by 100% with the new springs.

 

The original springs in the M1A1 were fine, they could be reused and I set them aside for spares.

 

I think it's worth checking the springs, 70 years is plenty of time for a spring to go belly up. Especially the recoil spring.

[Boone97]

I was working on this issue today with my Kahr M1SB. The two holes in the trigger frame were in fact a mess, so I cleaned those out. I'm still having the problem though. I ordered some GI springs, instead of the current production Auto Ordnance. Should they fit a bit better? Thanks!

[Adg105200]

I was working on this issue today with my Kahr M1SB. The two holes in the trigger frame were in fact a mess, so I cleaned those out. I'm still having the problem though. I ordered some GI springs, instead of the current production Auto Ordnance. Should they fit a bit better? Thanks!

Possibly. How does the OE Kahr spring look? Does the tip of the spring coil fully engage the guide hole? Or does it seem too short?

 

Andrew

[Boone97]

Well, I had a couple OE springs, and they would compress so much I couldn't remove them from the mag catch after installing them just once. If I had to guess, I'd say they were just a little larger than they should have been to fit in the hole around the mag catch shaft.

I cleaned up a ton of mess in the slot between the two holes. It may need some more polishing.

[reconbob]

. You will not find an original spring from any of the big suppliers. They all sell repros

and list them as original because how would you know? The exception may be Don at

Omega.

I have cotinued to study this because it happens a lot when we assemble the

trigger frames for the blank guns.

Frequently the mag catch will lift out of the hole with any movement of the

lever. The lever hits the front pin of the pivot plate but this limited movement

can be rnough for the cstch to lift slightly out of the hole and not snap back.

Sometimes its so bad that if you push in the pin on the pivot plate so the lever

rotates farther Each time you rotate the lever it will lift farther until it actually comes

out of the hole.

For some reason this does not happen much with GI frames.

I still have not got the definitive answer but now I realize that part of the problem

is that the round part of the catch that clicks into the magazine must always be in

contact with the lever side of the hole thru the front of the frame. If the round part

is always rubbing on the side of the hole the catch cannot lift out. If there even a

little space the round part will lift against the side of the hole and likely hang up

and not snap back.

Now many GI frames have catches which do not stay in contact with the side

of the hole and yet do not lift out at all so in some way there is no compression

on the spring in that direction....

 

Bob

[Boone97]

Well, the "new old stock" springs didn't do the trick. The problem persists. So at that point, I filed a little off the left side of the mag catch (when holding the gun in regular fashion) and it improved it a bit.

Dan Block is cutting me a mag catch....I'm hoping it won't have the same problem. I understand he's downright gifted.

That said, I bought the gun for reenacting, and this has been the only issue. And admittedly, it's a band-aid mod I'm doing because I'm offended by the idea of spending $70 on a new Auto Ordnance mag. It's not my SHTF gun, it's a toy, so I'm trying not to let my OCD perfectionism get to me over it.

[ppgcowboy]

Have you taken a diamond file and smoothed the end of the spring of any burrs?