The following text is extracted from "Handbook of Rifle Shooting" by Alex Lord Russell (1869, Toronto). It provides contemporary description of the late form of Rigby muzzle loading match rifle.
The Rigby Rifle
Since 1867 Mr. Rigby has adopted the shallow grooving and hardened bullet with a very decided improvement in the shooting. Diameter of bore, .451; largest diameter, .480. No. of grooves, 8. Grooving very shallow; lands narrow, about 1/4 width of grooves. Uniform twist, one turn in 22 inches. The form of grooving renders it impossible, it is said, for the bullet to strip. Bullet, 530 grains, hard metal, solid base, felt wads; powder, 90 grains, Curtis and Harveys No. 6. Mr. Rigby recommends and supplies a loading muzzle with his match rifles. At 1000 yards at an official trial at Woolwich, the low trajectory of his rifle was evident from the small elevation required - 2 deg. 44 min. Many of the principal prizes in 1867 were won by this rifle. For a new match rifle complete, the charge is 22 guineas; new barrel and breech fitted, 10 guineas. In the International Match of 1868, among 24 competitors, 14 used the Rigby Rifle.