Yea that blank would work we will need to chamber it and turn it and every thing else but its a good start. you could do a bull barrel or a heavier weight like around 3/4" or what ever a RPK barrel uses for a GB and hand guard retainer.
that barrel might be just the ticket for a 450 bushmaster also. brass is out for it now an Im sure there are reamers. Id have to research the twist.
wish they had a .358 barrel cheap. Im thinking about a 9mm-08 using my 358 win reamer on one of there 9mm barrels. Id have to get it converted to a removable pilot. it would be a fun gun to shoot cast bullets in.