I had the same creep on my new NMBH, plus it failed to carry up when cocked slowly.
It wasn't gritty just creep.
Tried boosting the hammer, did the poormans trigger job, even filled the action with a very fine polishing compound and went through about 1000 cycles, NADA, NIX,ZERO ZILCH,DIDN'T PASS GO AND DIDN'T COLLECT ANY THING BUT DUST, and it took forever to get all that %$#@$ out of the action.
The only way your gonna get rid of the creep is to reshape the trigger to hammer sear angle and that ain't no job for a hobby gunsmith . But there is hope and you can do this yourself.
I bought a Power Custom Bisley trigger, hammer ,spring kit and it was worth every bit of the $$$$. Installed it myself and it took care of the carry up problem too. I kept the original hammer spring but used the lighter trigger return spring, and added the extra power base pin latch spring. You have to modify the Bisley trigger to fit the BH grip frame, it's easy, you just can't let it get hot.
The trigger lets off at 3.5# zero creep, and can't be jarred off and is 100% safe, plus it has the added 1/2 cock feature and the chambers line up at the loading gate with the clicks, plus it sounds like a Colt when you cock it.
I did the free spin mod on the hand (pawl) but didn't like not having the clicks when the cylinder is turned with the loading gate open, so I ordered a new hand when I ordered the kit. Replaced the aluminum ejector rod housing and rod with a steel housing and bullseye rod.
Next will be a steel grip frame in the original NMBH shape, I hate those aluminum parts, wish Ruger would wise up and make 'em all steel,I would gladly pay the extra $$.
It's almost a custom, can't afford a Linebaugh !