.308 and 7.62 NATO are the same round. In a sense, yes, they are comparable. Obviously the rifle will be fed by magazine whereas the light machine gun is belt-fed, but the rounds are the same dimensions.
About $450- and it is spelled Mossberg.
You will have to call Mossberg
200 or so
Mossberg
The Baikal is chambered in .223, .308, .30-06, and .222
mossberg 595 bolt
Local gunsmiths, gun shows, e-gunparts.com, Mossberg... those are the places to try first.
mossberg for western auto
300 or so
50-350 usd
it should shoot 1inch or better three shot group at 100 yards. try different bullet weights.
Not economically feasible.