Let's start with the easy question. Any moly prep that is in an oil based carrier is of little use. I have heard that there is one maybe two in an alcohol or solvent that evaporates without leaving a residue.
The oil will make the barrel shoot like crap until the oil is shot out. No different then shooting an oily bore (WD40, Kroil, whatever). You need a clean dry bore.
Bore preps are ok but I have not found it necessary. Shooting solves that for you.
Do you need to moly bullets to improve accuracy? NOPE.
Can it help in production or rough barrels? YEP.
I use a lot of moly bullets because it is easy to do, really doesn't prove a negative and can offer some benefits in consistency. Many barrels today are made so well that moly really doesn't help the fouling much (barrels don't foul that much to begin with).
Thing to consider if you moly: You don't want to be cleaning down to bare metal ever again. That just eliminates the moly layer which is why you coat the bullets in the first place. If using modern clean burning powders, cleaning becomes very infrequent and can usually be achieved with a dry stiff nylon brush.
If you have a rough bore, moly will help you achieve predicted performance without excessive pressures. It is simply a high pressure lubricant. Works wonders in military bolt rifles.
If you live in very humid environments or hunt in conditions where your bore can get wet or rust a threat, DO NOT USE MOLY. Reason is that you need to protect that bore with some form of rust inhibitor. That just screws up the moly layer. I live in a very dry environment so do not need to oil my bore after use. In fact, most of my rifles don't have any bore care at all except maybe dry brushing every 100 rds or so to maintain accuracy.
I do not believe moly attracts moisture anymore then burnt powder. It retains being an extremely fine powder when exposed to atmosphere. If it attracted moisture, it would turn into a hard lump in short order.
There are no shortage of debates on this topic. It is not the end all and if you have quality smooth match barrels, a toss up to its use. It is messy, does require a different approach to bore care, does have benefits for helping with barrel consistency and reducing amount of needed cleaning.
Might help with barrel wear (that might be a stretch but at least it doesn't increase it).
I moly coat for my target rifles. I don't for my hunting rifles. I did for all my military rifle shooting except those with chrome lined bores.
Jerry
