J-random-occasional dry-firing won't hurt anything. Guys have been unloading rifles, closing bolts and pulling triggers for year after year after year with nothing bad happening.
It's possible, I guess, that steady dry-firing while practicing could cause some problem if snap caps aren't used. I've never heard of a problem which resulted from dry-firing, but I'd have to ask a gunsmith to say anything definitive.
Certainly, using a once-fired case when adjusting a trigger is as good as anything.
