Just invert the carbine and look at the witness hole underneath the trigger mech. You'll see how the mag catch is held in. Or you could look for a vid... Watch this one from the two minute mark.
You use the disassembly hole on the bottom of the trigger housing. It's nice if you have a padded vise to secure the carbine while working on it. Insert a small diameter punch or small screw driver into the hole, applying pressure towards the magazine catch. There is a spring loaded plunger that is applying pressure to the magazine catch. You need lever the plunger back enough for the plunger to release the magazine catch. The catch slides out to the side. Be careful of the plunger and spring, it can jet clean across the room if you lose control of it. As the plunger and spring also lock the safety in place once you remove the spring the safety comes right out. After cleaning the bores with a pipe cleaner you reassemble in reverse order. Safety, spring and plungers, then magazine catch. It's not hard, but can be a little fiddley.
For me, it's been a lot easier to do when the gun is completely assembled - makes it easier to hold onto, and less likely for other pins (held in place by the stock) to fall out. Sometimes the plunger and spring assembly will be stuck in place, then it's gets to be more of a challenge! - Bob
If this happens, plunger and spring assembly stuck, what's the next step
A small drift poked in and tap with a machinist hammer. You'll be able to get the mag catch out by prying the plunger back with a big jeweller's screwdriver. Then tap the stuck plunger and it'll pop out.
I've only had one that was really stuck and it was only the rear half of the plunger assembly, so there was no problem removing the mag catch. I can't remember if the safety would even come out at that point. I didn't want to ruin the plunger and spring assembly, so didn't apply any force from the mag catch end of the hole. Believe I did get the safety out without damaging it, but the plunger wasn't really accessible from the rear - even with the safety out of the way. I had already applied penetrating oil from both ends, so kept up with that, plus tapping on the trigger housing with a plastic hammer. Eventually I warmed it up a bit with a heat gun, and more work with the plastic hammer finally got it out.
Before inserting the new items you might put a swipe of grease on the surfaces that contact the plunger. It is a sliding unit so oil isn't appropriate. It will make even a rough safety work smoothly.
---------- Post added at 06:22 PM ---------- Previous post was at 06:12 PM ----------
Rainy day here in Ga.------- thought I would put up a few pic's on my, [I'm done M1A1].
Not trying to fool anyone by putting this carbine back to it's 1943 configuration, but that's the way it was.
It was kinda fun reading up and coming here to the forum for help and good advice.
Here's the post war parts I replaced with WW-2 parts and what the carbine look's like now.
I could have almost bought another carbine for the cost of the right parts, but it was a fun project.
Thanks for looking, and the advice.