U.S.Rifle Model 1917.As far as the rifle in question I would do a chamber cast.It can be chambered for almost anything.When DP P14's were available for $25.00 to $35.00 I built a number of rifles on them.Whether I used a P14 bolt or an M1917 bolt was determined by the rim size of the case I was rebarreling to.The actions can be made to handle the .505 Gibbs.The largest round I personally used was .416 Rigby.
If the rifle is in issue condition it may simply have the wrong bolt stuck in it by an importer.