[Azathoth]

3. I have only ever broken a selector plate on a g36 in the location that you describe. And that was my fault for trying to pry it from the gearbox without taking out the guts inside it first. I suspect that your problem is probably caused by an alignment issue between your gearbox and your body. If your fire selector is straining the selector plate you could try sanding off some material.

2. When I mean smoothing i mean lightly sanding or more accurately polishing with jewelers wax or with the finest grit sandpaper you can find. You want to make it look like a mirror ideally without removing too much material (as in nearly nothing). There is a guide on mechbox.com on doing this. PM oborous and he can send you a picture of his systema gearbox shell which is, and i'm not exaggerating, shiny enough for you to read a newpaper from the reflection (both inside and outside of the box). He must have spent days polishing it, but you don't have to go that far. Ask him about removing all the right angles at the cylinder head.

1. My trigger arm is different from yours. It will only fit 1 way. It's not symmetrical. I don't have my gun in pieces to illustrate this.