Possibly a Smith and Wesson model 1500DL. Either 270 or 30-06 or perhaps 7mm Rem mag as the barrel apppears fairly long. I know the calibre appears a bit small but they didn't come in larger calibres. The barrel does look quite slim as well. I say the 7mm Rem mag because they had the 24 inch barrel and this one does look longer than 22 inches.