Had a Bill Large .50 and it was about 1 in 90 at the breech and gradually increased to 10 inches from the muzzle to 1 in 30. Very good shooter.
Bill Large and I made the gain twist tooling in1960 and it shot really well.
It was quite a task and I wouldn't tackle it today.
N.G.Whitmore,maker of the U.S.Grant presentation rifle now in the Smithsonian
in DC used a gain twist that is unknown to me but his rifles were banned according
to Ned Roberts as being unfair competition.The Grant rifle when tested used a
picket bullet with circular linen patch and was 38 caliber with 12 grooves.
At 110 yards or 20 rods as it was called it hit a target the size of a percussion cap
box 10 consecutive shots.I tried to get Bill Large to copy this but he never did.
Harry Pope's gain twist on some barrels was 1in 16 and ended in 1 in 15.75.
I have shot one in 38 caliber in the mid 60's and off a rest using Pope's mould
for the bullet and breech seating it I was able to get under one inch easily with
scope sight.
Bob Roller