it's not possible. bittrex uses its data to calculate the lines, gunbot uses whatever data it's collected over the past 300(adjustable) cycles. they are both using different numbers to calculate the BBs. you can't get them to match.
i set bittrex to 15 minute candles and the BB period to somewhere between 12-18 and it tends to be fairly close a lot of the time.
i've heard some people say to set it to 50 but there is no way that's right. 50periods*15minute candles=750minutes which would be 12.5 hours of data.
my understanding is this. (i could be totally wrong)
gunbot is rarely using that much data to calculate its BBs. if you set gunbot to use 300 latest prices and have it collecting data every 20 seconds that would be 300*20=6000seconds = 100minutes worth of data.