Are you talking about the bayonet lug itself or the gas cylinder?
The gas cylinders are made of stainless steel which doesn't take parkerization too well and they were typically painted black. Its normal for them to be shiny or a different color than the rest of the rifle. You can try to take some steel wool to remove the rust, then cover the afflicted area with CLP. An M1 shouldn't rust unless its neglected- I've seen rifles that were pretty much in the white with no rust on them.

If you are going to have work done on it, from what I've heard, DGR is a great place to send it. I'm sending my trigger group there in a few weeks to have it worked on. Mil-tech is a more spit and shine place while DGR knows all of the ins and outs of the M1.



The consensus is that I'm wrong about factory ammo in the M1. I guessif it works for several people without problems, then it might be ok. I learn something new everyday.