Build Thread Going "Frankenstein" with H&K USP Triggers

Hybrid Slave · Apr 5, 2025

I have a USP40 with the light LEM trigger and a USP45 with the V3 (de-cock only) option.

I do not like the light LEM trigger on the USP40 for carry and would prefer the heavy LEM version. For now though, because of my short trigger finger being only slightly uncomfortable with the first long heavy V3 pull on the USP45, I think that the LEM kit in the USP40 would serve me better on the bigger USP45 (with the heavy TRS).

So I would like to remove the LEM trigger kit in the 40, and install it into the USP45 but with the heavy (TRS) LEM option. My understanding is that I only would need to purchase the heavy trigger return spring (around $20) to accomplish this.

And in the meantime, I would put all the parts that were in the 45 into the 40 making my USP40 a V3 (as my hands are more than comfortable with the smaller 40 frame).

My question is, with the purchase of the heavy trigger return spring (TRS) will I still have all the parts I need for two fully functional pistols as I've described?

Later (when money allows), I will either try to lighten up the heavy V3 DA pull on the USP40 (with whatever parts that may require) or , if I like the heavy LEM trigger (which I believe I will) just purchase another LEM kit and install it with the heavy TRS like the one I want to put in the 45.

In summary, I trying to avoid buying more parts than I need.

Can anyone with some know how with the USP give some comprehensive insight?