Adafruit sells a version of that motor that has a different gear train (around 1/4) of the standard that takes about 513.04 steps per rev, damn near drove me crazy, cause I didn't get the results expected, till I bought 2 of the "Real McCoy" 
Adafruit sells a version of that motor that has a different gear train (around 1/4) of the standard that takes about 513.04 steps per rev, damn near drove me crazy, cause I didn't get the results expected, till I bought 2 of the "Real McCoy"