I have a full-size USP in 45auto. Bouht it about 20 years ago. Single-action trigger is fine, but the double-action pull is heavy and gritty. Heavy is ok, but the gritty feel has to go. Any suggestions?

I do keep it cleen and well-lubed, so that is not part of the issue.

When I bought my USP with LEM trigger group, I think I remember there being some factory option to send it in for travel shortening or pull weight reduction, but perhaps I'm wrong. It was 10+ years ago. I'd need to pull out the box and papers to verify. I like every aspect of the gun so much that it's still at my hip every day now.

The folks at this link provided below have several ideas that you may want to check into. Good luck.
http://www.hkpro.com/forum/hk-handgun-talk/124398-hk-usp-trigger-job.html#/topics/124398?page=2

Buy the match trigger. It's worth it.