The answer is,,,,,,,,, if you have the later version that has the one piece extended mag tube, there are no barrel options for you.
Remington's response: Thank you for contacting Remington, and we apologize for the delay in responding! This variation of the 870 Tactical is designed as a tactical gun only. The placement of the barrel band does not allow it to interchange with barrels from the other 870 models. Our apologies.