In the early years Ruger didn't make their own barrels.I heard they used barrels from different manufacturers. So the quality was kinda spotty and you never knew whose barrel you had. Mine is .459 at the start of the throat. And has two constrictions in the barrel. One is where the barrel mounted sling swivel is located and the other is where the front sight is located. So am seriously thinking of getting it fitted with a 24" barrel and throated as well. Don't think that there is enough wood in the Alexander Henry forend to allow it to take an octagon barrel of about a Winchester #3 weight barrel.Thanks,Frank