Changing from factory Heavy FPBS will knock the pull weight down about 1.5 lbs. Changing the Heavy TRS will reduce it by 1.9 lbs. You can pick and choose which one to swap out to be within your desired pull weight, with the FPBS being the easiest. The TRS is harder, can be done with a set of small, needle-nose pliers, or easy with the HKParts' TRS Tool.
TooSixy: Please explain how the Heavy FPBS increases the trigger pull weight. I'm learning and don't see how that spring applies any nforce on the trigger. Thank you.
Replacing the LEM FPB spring with the regular FPB spring lowers the trigger pull weight of the last 3rd or quarter of trigger travel. For me it is less of a wall when getting close to releasing the hammer and a lighter trigger pull if shooting from the sear reset. I hope that helps. If not let me know and I'll try to clarify further.