In the SNBC BTP-M300 programming manual see pages 3, and 4

Page 3 — “ESC J n”
This sections shows how to determine the amount to feed the paper after printing in increments of 0.176mm
Use the hex code 1B4A32 to print 88mm between lines.

Page 4 — “ESC d n”
This section shows how to print an amount of character lines as blank lines (probably what you want)
Use the hex code 1B6402 will feed two character lines after printing, 1B6401 will feed one

I don’t know if I have one around to test but hope this helps

http://www.crs-usa.com/DEALER/snbc/btp-m300/BTP-M300_Programming_Manual_V1.0.pdf