Blu97 said it was a No. 4 barrel, not a M1917 barrel. Anyway the No. 4 twist rate is normally 1 turn in 10 inches (1:10), left hand. Some Savage barrels are 1:10.5 and some Long Branch barrels are right hand twist, but neither matters for practical purposes.
The usual way of measuring twist is to take a cleaning rod and use a patch tight enough to be sure the rod turns with the rifling. Then insert the rod into the barrel, and mark one side of the rod at the muzzle. Pull the rod out, letting it turn with the rifling. When the mark is once again on the same side, measure the difference between it and the muzzle. That is the rifling twist. For rifles of .30 or .303, it is usually 1 turn in 10 inches, so the distance measured should be 10".
Jim