[goodsteel]

I dont mean to stick my nose into a gunsmithing project that I have never done, but I would like to sugest that welding is the most harsh way to attach anyhting to a firearm (I realize, not knowing exactly what you are attempting here, that may not be an option on this project)
However, if you need to stick two pieces of metal together you can:
Glue with 2216, red locktite or similar.
Solder with low heat solder.
Silver solder.
Or braze.
Any of the above methods would give you a simi-permanent/permanent joint that would look sharp and work well.
Just my 2 cents worth. Might be worth a try.

[triggerjob]

Fire arms welding should be done with a TIG setup, to absolutely minimize the heat effected zone. Personally I would not attempt this with a wire feed setup unless you are skilled at welding sheet metal, if you did have the skill, youd probly also have a TIG torch.

The best way to do what you want and have a good clean job is to cut off the site using your dremmel or foredom tool, clean up all the burrs, rough up both mating surfaces, and then silver solder the site in place.

You arent familiar with silver soldering, trust me theres more to it than torch and solder, then just use JB Weld, or ACRA GLASS, if you use expoxy, and thouroughly clean both parts and follow the mixing instructions it will work great wear like iron, also it can be removed simply with a torche.

[triggerjob]

One more thing, CETMEs are supposed to adjust for windage at the front site, so before you muck up your rifle, look at the front post, it ought to turn, the post is set off center so as it rotates it moves off center sort of like and orbit. Check this out first before cutting the spot welds on your rear site.