I picked up an Investarms "Gemmer" rifle in .54 a few months back. The trigger is horrible .. setting the set trigger must be 20 pounds or more. The hammer seems to be a smidge off center as well. I'm thinking about replacing the trigger and/or lock. Can anyone offer feedback, good or bad, about R.E. Davis triggers and locks? I emailed a few days back and haven't gotten a response. Is this normal with them? I'm trying to find out if they offer drop in units or if they have to be fitted and which to order if there is are drop-in option.

Davis are fine locks, no question. Have you considered Jim Chambers as well? Just sayin'...broaden your horizons young man.

also L&R locks. L&R makes "drop-in" locks for many makes.
the Gemmer lock should be a good one and the trigger can be adjusted.
remove the trigger group. the trigger spring has a screw at the back. back out this screw to lighten the set trigger. once at an workable weight lock tite the screw.

L&R as well as Davis are good
The Davis trigger I think is probably the better choice.

There are some information on other sites about tuning the lock you have, by polishing some internal parts. I've several of them and usually by tweaking the set trigger screw they dial in pretty good as was previously stated.
If you do replace and want to sell the original equipment give me a holler. Always needing parts.

Have you checked with Track of the Wolf to see what they have ?