BCRider, if i do go with a minimalist aproach, could it be that i have to re-oil during a session?
When i put the bare minimum as you desribed, at the end of day the pistol would be really dry, and the rails had residue of dryed up lube.
This was using Mpro. We have to keep in mind that these sessions we're 300-500 round ones, with some rapid fire along the way.
I haven't used MPro so I can't say what it's like. I do know that using the modern day synthetic grease I've got that the rails are still lubricated well enough at the end of a couple of 200 round days. Some has gone away but there is still enough to do the job. If I use oil instead of grease then yes, I do find that by the time I've shot something up around 200 to 250 rounds that the oil left is very minimal and the gun certainly does feel drier than I like. Which is why I shifted over to grease.
Even with the way the rails feel though don't think that the metal is totally dry. Years back in an article in a motorcycle magazine on lubrication an oil engineer stated that a fully functional lubricating and corrosion protective film is produced by one single drop of oil spread out over a square foot of surface area. And there most certainly is not a whole square foot of area inside a gun even allowing for all the shapes, nooks and crannies.
Modern oils that are not cooking oils or intended for wood finishing simply don't "dry out" or burn dry in anything less than many years of being exposed or during seriously hot conditions. As in hot enough that you would need welding gloves to hold onto your gun. So the dry crusty bits you see are likely a gunk formed from oil and fouling residue. And with all the fouling that blows back it's no wonder.
Part of the issue is that in our lack of appreciation for how little it takes to lubricate and protect that we slather the stuff on until we feel it have an effect. But that effect we feel is called "viscous drag". And what the excess does, if it doesn't simply drain away, is slow down the gun by providing a shock absorber like drag. A good example is walking then running in air vs walking and running in a swimming pool. Walking is fairly easy in either. But running in the pool becomes very hard vs running in air. Butter enough oil or grease on the gun and it becomes very much like trying to run in the pool.
Another example of all this is to use some brake cleaner or other full degreaser to totally dry your gun. I mean totally grease and oil free. Now cycle the slide and feel how sticky it is. That's the metal of the rails and other parts binding together due to no lubrication. Now put on the lightest possible amount of oil. For this I mean two drops on a cleaning patch. Rub the patch vigorously into the rails simply to ensure it is spread out evenly and on the hammer slide track of the slide if your gun has a hammer. Now cycle the gun and feel how much more slick it is. That is all it really needs.
If you add more to where the slide feels slick and quiet what you've done isn't lubricate it any better. Instead you have added enough viscous cushioning that you simply can't feel the slight rattle produced by the clearances. But while the thin film will hold onto the metal tenaciously a thick film is simply blown or shook off until it becomes a thin film. Which is why a generously oiled gun becomes dry feeling quickly. It's not really dry, it just doesn't have a thick cushioning film any longer so it FEELS dry to us when we rack the slide. But that thin film that holds on for dear life is still there and doing the job.