Looking for a couple pointers in regards to material and welding characteristics

My friend brought me a Walther PPK that his grandpa had left him. He was having trouble with the magazine. It wouldn't lock into place. So I broke it down and inspected it and found that the magazine release mechanism was showing some visible signs of wear. It had worn down just enough that it no longer engaged with the magazine. I looked up the part and found 1 for him for like $25. After I ordered the part for him I was thinking about it and had an idea of a possible fix. He's still going to get the replacement part but the idea I had to repair it that kind of peaked my interest and it seems like a good opportunity for me to get some practice with something that is much on a smaller scale than I'm used to. The original part has been worn down about .010-.015" over a surface area of approximately .015"². My idea is to TIG a small bead onto that area and use my lathe and mill to remove any excess material. The machining aspect is pretty straight forward, but I have a few questions in regards to the welding.
-Does anybody know what grade of material was likely used?
I know that it's ferritic stainless steel because it does attract to a magnet, but I'm hoping to be able to check out a datasheet so I can get the specs.
If it helps to narrow down the possibilities, it was manufactured sometime during WWII.
-Would it be ok to use 316 stainless filler?
-Is there anything that I should anticipate that could arise from the heating and cooling that the part would experience through the welding process? for example, how cast iron becomes so much harder and needs to be cooled gradually or it may crack after welding it
Any suggestions, advice, or help is greatly appreciated. Thanks and have a good one.

There are whole books on weld induced heat effected metallurgy and most of your variables are unknown.

A ferritic stainless isn't particularly hardenable, which I'd imagine you'd want in a latch.
17-4 stainless is a magnetic martensitic precipitation hardened stainless.


Not sure 17-4 fits the timeline, but I do imagine re-heat treatment should play some roll if it's to last as long as the first one

Early Martensitic Stainless fit the timeline https://en.m.wikipedia.org/wiki/Martensitic_stainless_steel

And would be magnetic

@IceCzar Thank you, this info was exactly what I was looking for. I appreciate that you took the time.