I purchased this Spencer Sporter in Gettysburg a few years ago. The seller said it was 20 gauge which I knew it wasn’t. I can’t find any history or records of this rifle and am looking for some help. 

It appears to be built off a 1865 carbine based on the presence of the magazine cut off, base where the sling ring would be, the ribbing on the magazine tube and a wooden plug where the barrel band spring would be. However the normal markings on a carbine are not present. 

The serial number is 13923 shown on the tang and is on the barrel under the forearm and that is the only markings. No caliber, no maker, no proofing. 

It is smooth bore measuring roughly 0.563”at the chamber and 0.656” at the muzzle with a 30” barrel. It has a rimfire block which appears to be original and as aged as everything else. 

I know Spencer produced limited rounds of 56-56 and 56-50 rimfire shot shell but the chamber looks too long for the regular length of the cartridge. Along with the muzzle being too wide for the limited number of pellets. I’m guessing it is a 32 gauge shotgun but I can’t prove it. 

Any information is greatly appreciated I would love to get this shotgun shooting again as the action is tight and very mechanically sound. 

Information on Spencer Sporter