For target shooting with today's "little" loads that most people want to use, spit will give the best accuracy - in literally, every rifle barrel or gun I've ever shot and thats a bunch.
Once you start slicking things up with slippery substances like oils, greases, etc, you need more powder or the gun starts throwing shots. Believe me on this. Slicker lubes require more powder, just as slicker bores need more powder. Of the slick lubes, I've found nothing to beat LehighValley Lube - but - it took 15gr. more powder than the accuracy load with spit, to do it. My test guns were a .45/42"bl. and a .40 cal. w/36" bl.
Of course, I am referring to loads that do not require any wiping - ever, while shooting.
There is a simple formula for that - works in every rifle (I've ever worked with) - ball, .010" (with .010" -.012" rifling) or peferrably .005" (with both shallow square or deeper .016" rounded rifling) under bore size, with a 10oz to 12oz Denim patch - measuring .020" to .0225" - or ticking .0215" to .0225"- all hard SQUEEZED Caliper measured.
Almost everyone at our range shoots similar loads - virtually identical, actually, except for 2(3 counting me in one gun) . One guys patches run around .015" and things get sitcky loading after about 30 or 40 shots - he has trouble - light loads, too. The other, Len, is using .028" to .030"(HEAVY ticking) with a .535" ball in a square bottomed Getz barrel - loads with short starter and tapered rifle's rod - 3/8" at the small end, that goes down the bore first. He has no difficulty loading - all day. I guess I fit there as well as the third, with my .69 - .030" patch, with ball .006" smaller than the bore(.684") in .012" rifling - yeah- .015" compression each side, in the bottom of each groove. It also will shoot into 1"" to 1.5" at 100 meters off bags - with open iron sights - single front bag under my left hand. Snug loading is good, but tight really starts to shoot.