If you used the gun in self-defense, trigger pull is irrelevant. After all, you're claiming you intended to pull the trigger.
It's not irrelevant if the prosecutor attempts to prove that your claim of intent is inaccurate. That's one of the reasons that going to significantly lighter triggers can carry potential risk. If the prosecutor can "prove" that you didn't fire intentionally then he's also, by default, proved that you didn't fire in self-defense since self-defense is an intentional act, not an unintentional one. If your claim of self-defense is not supported by the evidence then you shot someone without justification. That's a bad thing.
However, in this case, the OP is actually talking about making the trigger heavier, so he's unlikely to run into problems, in my opinion.