My guess is a No.8 with a No.7 muzzle section spliced to the barrel with some lathe work. What they call a "pit ring" in the bore could be a seam. Shortened No.4 front wood. Looks well done. Any thoughts?
SMLE No. 8 MK 1 .22 LR Rifle 22 : Curios & Relics at GunBroker.com