The bbl is about 17 1/2",,,the standard M1903 6.5mm carbine,,if there is any such thing as a standard for these (?).

Easy way to 'rough' measure M/S bbls if you don't have a rod or measuring devise that'll slip down the bore is from the center of the front 'guard' screw to the muzzle.
That screw enters the action right about at the point that the chamber face is located inside the breech area.

A 40" blank is most likely going to be needed anyway. A bit of shifting the pattern around, the operator needs a little extra to clamp onto the blank while working on it ect.

No trigger(s) in mine,,missing from the project box-o-parts. The stock hasn't been inletted for any trigger, single or DST.
I'm going to put a single trigger into it.,,have the parts on the way.
That and a 1/2 stock will make it a bit unique.
I figure no use doing all this work to make up something that's already available for sale at most any decent gunshow.
Plus, I could look forever and never find one!