It looks like there is a factory option to get the LEM variant at 4.5 pounds. With a little TLC form an HK armorer, you could probably get it really smooth.
The P30 Trigger Variants
P30:
Innovative safety trigger with concealed cocking piece in the spurred hammer. Centrally located de-cocking button, with a constant Combat Defense Action (CDA)* trigger pull of approximately 20 Newtons (4.5 pounds), without operation of the de-cocking latch, and defined let-off point.
P30 V1:
Innovative safety trigger with concealed cocking piece in the spurrless hammer, without de-cocking button. Constant CDA/LEM trigger pull of approximately 20 N (4.5 pounds) and defined let-off point.
P30 V2:
Like P30 V1 but with CDA/LEM trigger pull of approximately 32.5 N (7.3 pounds).
P30 V3:
Conventional single action/double action (SA/DA) trigger without cocking piece in the hammer with spur and centrally located de-cocking button.
P30 V4:
Like P30 V1, however CDA/LEM trigger pull approximately 27.5 N (6.2 pounds).
P30 V6:
Conventional double action only (DAO) trigger without cocking piece in the spurrless hammer. Constant DAO trigger pull of approx. 39 N (8.8 pounds).
Not all variants available in some regions.
* also known as Law Enforcement Modification (LEM)