Prob'ly 1 turn in 14 inches.
If you have the rifle you can find-out for your self, a tight fitting patch and a cleaning rod. Mark a thin, straight line down the length of the rod, get the patch into the barrel, mark the rod, gently push the rod into the barrel until it has completed one revolution, now mark the rod again, extract and measure between the marks.
"what bullet will give the best results?" sorta depends on what results you are looking for, match shooting, varmiting, pelts, Cape buffalo?