Bill, the gentlemen who examined this smooth rifle, and who compared it to the Marshall rifle and signed Albrecht rifle felt this probably used components from a private militia or officer's fusil - whether restocked, or stocked up with those type components. I don't know if the barrel dimensions given fit a finished barrel from such an arm, or if the barrel was shortened from a longer tube.
They felt and I agree that this piece was stocked at this length - in this configuration. The design and spacing of components look appropriate. Also the stocking appears to be very close to that of the Marshall rifle with a similar length barrel. Remnant bits of carving remain, suggesting a fully carved rifle similar to the Marshall and others from Bethlehem or C's Spring. The rifle stock form with carving and the double triggers go together well, but a .75 smooth barrel is not what we think of as a target rifle! It certainly is an interesting piece, and we look forward to your version. Bob