Plasma spray was the original term for what is being called a 'sprayed on weld' here, useful for rebuilding crank pins on locomotive crankshafts and other applications that involve very expensive parts being repaired to original dimensions, and in some cases to better than original, from a duribility perspective. The equipment is not inexpensive and like most forms of precision work requires expertise for best results. As in welding, a broad selection of materials is available for use with this method. I would strongly suspect the work is being subcontracted out for any gun related repairs, but would have no reason to think the end result would not be satisfactory.
Here is a good link on the subject:
http://www.matscieng.sunysb.edu/tsl/thermal/article1.html