I recently purchased several gunsmith-built rolling block rifles that came from Sweden. One is a 24 gauge with straight rifling, one is some indeterminate long .45ish cartridge and then this:

Not a very sexy sporting rifle, I admit, but it intrigues me nevertheless. It has a 34.25 Octagonal barrel. Very good bore. Built on a 1875 crown S receiver from a M64-68 military rolling block. Nicely figured wood. No cracks. Needs buttplate fitted. Chamber cast indicates case very near .38-55, but with a .360 bore??? It could be a .360 2" Black Powder Express, but I cannot find specific info. on the shorter .360 case. Based on a chamber cast, the base is .435, neck is .380 and length is 2.09. Seems that .38-55 brass could be slightly trimmed and front half sized down with .38 Spl. die, cases fire formed and .38 Spl. dies used to expand and seat a 145 gr hollow base .357 dia. bullet available from Buffalo Arms.

I am looking for some dimensional information on this round or any advise on getting this rifle shooting. Thank in advance.