i have messed with a few mosins before. i successfully turned a clunker into a tack driver by cutting the barrel down and recrowning it. my new plan id like to go with the archangel stock and turn it down for putting the bayonet in it and cut the barrel down but put the front sight back on. im a fairly good welder would i have to heat everything to weld it or just have at it?

A small tack weld with a mig welder or even with a very thin welding rod should make no difference.  If you were welding in the middle of the barrel,it probably would but at the end of the barrel, I wouldn't worry about it.  I would tack on only one side though to allow the barrel and sight to move independently on the other side.  It's probably not that critical but if you weld both sides or all the way around, when both parts cool, each will pull against the other.  In bigger parts, this can cause warping.

 

If I was doing this, I would probably drill and use a small roll pin instead.

I have 1100 and 500 degree solder. Most of the front sights i believe are silver soldered/brazed on.