brokfut, I agree with Shaky on several of his comments. First, if you are using a given load and change out only the bullets for moly coated bullets, I've found that YES you do loose speed and in most cases accuracy. And I agree also with him that I'm not sure which is worse moly fouling or copper fouling, I sorta think moly fouling is worse.
In rubbing elbows with some long range wildcat shooters they have showed me that they have got the speed and accuracy back by #1) Cleaning the barrel of ALL fouling, then using one of the following 3 methods and Moly coated bullets getting the speed back by A)hotter primers, B) a faster powder or C) CAREFULLY increasing the amount of powder that you are currently using. I can't argue with 'em, they can sure as He.. out shoot me in most cases.
Of course this will take a lot of careful work, planning, and shooting over a Chrony to give you the information you want or need. And is using moly worth all this???? I think it depends on who you ask.WD