Does the barrel have a proper crown, or was it cut off "square". Picture isn't very clear, but it looks like the latter. The front sight is not original, so it strongly suggests that the barrel was whacked by Bubba, since, if the gun already had a 26" barrel with correct crown and proper front sight, it would have been left alone.

Reason for my asking is that, in 1902, 100 rifles were made up by SA, for trial, under the auspices of the Board of Ordnance and Fortifications, with 26" barrels. They are quite rare, as you might expect, and your serial number is very close to one of the small clusters of known numbers, totaling 21 at present. I own 388786.