I remember seeing something, some time ago, to the effect that it is against federal law to return a "de-milled" military firearm to shooting condition. Recently, I've seen a number of 03a3 receivers that were "salvaged" from drill rifles, being offered for sale in several different venues. The only apparent damage they seem to have is the marks where the cutoff switch was welded in place, and then subsequently removed by the sellers. Are these receivers legal to use for a "shooter" build, or should they be avoided due to legal or safety issues? Thanks in advance for any input anyone may have.