Some discussions elsewhere recently made me think this topic deserves a thread of it's own, so here goes.
The mission is to develop a temperature-insensitive boolit lube primarily for hunting rifles with a goal of accuracy on par with the best lube formulas currently available in for temperature extreme, from below freezing to 100+ degree Texas (or anywhere else) heat, and in the temperate zone between the extremes as well. The lube needs to address, specifically, the common phenom of first-shot or "cold barrel" flyers while also being relatively immune to "lube purging" or progressive layering and purging in a barrel, and also be consistent through long strings of shooting and cumulative barrel heat.
Some lube formulas are excellent at either temperature extreme and some only in between, exhibiting all of the desired properties outlined above, but none that I'm aware of will perform to my satisfaction in all temperture ranges.
The problem in achieving a universal "wonder lube", from my limited perspective, is twofold: First, the "carrier" in most lube formulas has a narrow range of temperature for ideal performance, and second, very few people, least of all me, seem to have a good grasp of exactly what a boolit lube actually DOES. It's very difficult to manipulate a substance for certain attributes when one doesn't know exactly what mechanisms are at play which affect the outcome. This thread is intended to explore these mechanisms and hopefully lead to not only a better understanding of current formulas, but perhaps to better formulas themselves.
I'd like to postulate on the properties of a good boolit lube and the things that do work to achieve them, along with some theorizing of what lube is really doing. This is not presented as absolute fact, but only as a sort of summary of my own understanding of what's going on with boolit lube.
I believe that a boolit lube does two basic things to assist a cast boolit from a piece of fixed ammunition to its target: It provides a delicate and dynamic gas seal between the boolit and the barrel, thus preventing lead deposits from microscopic (or worse) powder gas leaks and the resulting gas abrasion of the boolit. The lube also acts as a film lubricant, preventing metal-to-metal contact in the rifle's bore. This last may appear simple, but lots of shooting with various lube formulas and bore conditions has proven to me that the surface upon which a boolit rides is absolutely critical to accuracy, and the ability of a lube to leave a consistent bore condition under extreme conditions and through long strings of firing is a key attribute of a good lube.
So, from cartridge case to target a lube must seal the bore like engine oil seals compression in a reciprocating engine, it must provide a consistent runway surface (for consistent friction), and it must either remain in the grooves all the way to the target or leave the boolit immediately and completely upon muzzle exit once its job in the barrel is completed so it doesn't affect the balance of the boolit on the free path to the target.
In order to do this, a boolit lube must:
1. Have the correct viscosity to match the pressure sealing requirements of a given load and alloy,
2. Have the correct amount of "drag" each shot, which may be a factor of both viscosity and lubricity,
3. Have the correct lubricity to maintain consistent bore surface,
4 Maintain the correct viscosity and lubricity through temperature extremes of both atmosphere, chamber, and barrel,
5. Have enough tack to stick to a boolit during handling, storage, and loading,
6. Not have so much tack that it only partially jettisons in flight.
7. Some other things that strike me as important are the ability of a lube to be left in a barrel without danger of corrosion, no "weeping" of oils in the heat to contaminate powder, no bad reaction with the cartridge brass during long-term storage, immunity to humidity, and compatibility with standard lube application equipment.
Traditionally, it seems that the trend in recipes has been to start with a "carrier" which is a foundation for the lube, usually a wax of some sort, which will absorb lubricating oils within its structure like a sponge and deliver them to the barrel while providing some substance to the liquid oils such that they can be installed in the grooves. This "substance" is the overall viscosity which also seems to aid the "stop leak" attributes so necessary to a good lube formula. Other things are added to modify the properties of these two general classes of lube ingredients or to add desireable properties of their own, such as graphite, carnauba wax, moly disulfide, etc. Some additives, like metal or organic soaps, are almost a third class unto themselves that I would call "binders". The various Aloxes and many EP greases contain calcium soaps, and the lithium soaps also make the greases sometimes used in lubes a carrier/lube combination unto themselves. Stearates also apply to this class, sodium stearate and stearic acid come to mind, there are others. These soaps provide lubricating properties of their own, and also can serve to bind lube ingredients together in a robust, homogenous mix.
The big issue for me has been to get all the properties of the 1-7 list in a lube with the commonly used and understood lube ingredients, and here's where the discussion gets interesting. What does each ingredient do, what is the failure point, how does it fail, and how can a formula be put together that will offer better all-season performance than the usual suspects of lube recipes?
Let that soak in for a minute and I'll start another post with a discussion of some formulas I use and why I think they work, and why they have limits.