While that is clearly not the case here, it is a good idea to bear in mind that 1917's were once dregs on the market and dirt cheap, so many were rebored, rebarrelled and other wise converted to other calibers. Most of those were also sporterized in other ways, but with the increase in collectability, some have been "restored" without changing the barrel. So finding one in something like .338-06 or .35 Whelan is not impossible. Of course, .30-'06 ammo will not shoot very well in such a gun.

Jim