Say down the road I want to restrict the gas port on the barrel of my AR.  Could I thread a small portion of it and screw in a small short set screw, tac weld the edge in a spot or two (I TIG weld) obviously clean that up and then drill the diameter hole I'm after in the set screw, put everything back and it be fine?

Would the hole in the set screw erode faster than the barrel material? I ask as the manufacture I used, chose a somewhat large sized gas port to ensure weak ammo cycles the rifle, but say some point in the future I wanted to restrict the hole would this be the best way to go about it? Just thinking about how I'd do it and that's whatnot came up with.

Edited to fix smartphone autocorrect confusion.

Is there some reason you could not use a quality adjustable gas block?
ETA -- I think autocorrect made your post confusing.  You want to insert a set screw, weld it in, then drill it out for a certain gas port size?  Either way, I would go with an adjustable gas block.

Yes that's what I want to do. The rifle uses a standard FSB so adjustable block is not desired or applicable.

Then pick up an adjustable gas key or bolt carrier group.

ETA:. You are one of the relics like me that prefer our FSB still....

I really wanted to fix the issue of to much gas, I'm guessing those BCG are capable of bleeding off more gas than a standard BCG to reduce the delta (pressure deferential) and thus force pushing the BCG rearward?

This isn't something I currently NEED to do, but it's something I may need or want to down the road so I was giving it some thought.

ETA nothing beats a pinned FSB. Even if you want to modernize it later,  just cut the sight tower and have a pinned gas block.

It is trivial to convert a front sight base into an adjustable gas block. Much easier than what you are proposing.

Example

Neat and functional... I might consider that an option if it turns out I need to do this.  But that is an eye sore. Thanks for posting it though i hadn't considered adding a restriction to the FSB rather than the barrel gas port. I might try something with the port in the FSB if I feel its over gassed now after you posting that.