I don't think there's as large a disagreement here about oil in a clean barrel as might be. IMHO, a light coat means I dry patch before firing, but don't scrupulously attempt to get it all out, as with a flush with solvent or alcohol to remove any/all traces of oil.
As for .311 bullets in a .308 bore, that's not such a cut and dried nono either. That happens every day with 7.62x39's all over the world, and especially with American made barrels chambered for this cartridge, which are frequently fired with foreign (.311-ish) ammo in their .308 bores. Swapping bullet diameters between 9mm (.355), .38 (.357), and .35 (.358) caliber bores is another instance that's actually a lot more common than many believe. Palma, etc., shooters play games with bore diameters and bullet diameters as well.
The oil may be incompressible, but bullets are, and barrels are also elastic.
At full chamber pressure the barrel does expand and the bullet does foreshorten and expand to accommodate that expansion. That's simply an attribute of the obturation process. Trust me, you slam a bullet with 50,000-70,000 PSI inside a force-fit bore, and dimensions are gonna vary all the way down the bore in direct relation to the pressure curve. All that an effective lube is going to accomplish is to reduce friction, decrease bullet diameter, which in turn reduces pressure. Less pressure for a given powder charge means, pretty much always, less velocity. That's what drives max powder charge limitations, and why lubes like Moly add complexity (and perhaps confusion) to these relationships. This is also why some shorter barrels shoot faster than some longer ones; the bullet/bore fit is also a key factor in a specific barrel's ability at achieving its actual velocity.
Some subsonics shooters will even wet down their bores with water and achieve (some) diminution in acoustic pressures without actually employing a
suppressor. I wouldn't, but the phenomenon has been observed and reported on this site.
Greg
