I just bought a 17 Gen4 and would like to set it up for IDPA SSP. I reload so I can load to an efficient level for IDPA SSP. I think I need to have an RSA with 13# springs. I see a lot written on captured vs. un-captured springs. I don't understand the difference as I am new to IDPA and Glock. I don't want to reassemble an RSA in the field. Just when I think I have a grasp on understanding, I read where this particular guide rod can be assembled either captured or uncaptured. I think I need some advice here.