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If you google "308 Norma ammuntion" you will have a start
Try e-gunparts.com, gun shows, gun shops, want ads. for sale ads.
Yes
1960
100-400
100-1000 usd
Doubtful. The .308 Norma Mag was a fairly short lived cartridge, and competed with Weatherby's own line of magnum rifle calibers.
A Browning safari grade bolt action rifle in the excellent condition you describe will bring between 1,375-1,500 dollars for a gun with between 90%-95% overall condition,and a good bore. There were not many of these rifles chambered for the .308 Norma Magnum caliber.
mossberg 595 bolt
50-1000 USD depending on specifics