Grey's #24 will be included in the shootout, thanks to a CBA member who volunteered to donate a sample. The good thing about Grey's #24 is that it is well known and respected in CBA circles, so that makes it a good reference point. The bad thing about Grey's #24 is that it is no longer available, so if it should "win" the shootout, that won't help us one iota in our search for a lube to replace HVR. Thoughts on leading and on so-called "lubrication":
this particular 7BR barrel does not lead appreciably with HVR, not even at 3000 fps. But it is possible that some of the other lubes in this test may lead, so let's go ahead and talk about leading.
I have observed at least 3 distinct kinds of leading in various firearms over the years:
1) leading near the peak pressure point due to failure to seal. In revolvers, this often shows up in the forcing cone, while in rifles it may appear 2" - 4" from the breech. Typically it leaves lead in the corners of the rifling grooves, and this lead can be difficult to remove, almost as if it were soldered in place, which may well be the case. This "peak pressure" leading is caused by hot gases blowing past the bullet. With a plain base bullet, the high combustion temperatures may actually melt the corner of the bullet base. There are several possible solutions, like coatings, gas checks, better fit, etc., but with regards to bullet lube, I think this is where a "sealant" type bullet lube can help, by functioning as a tough o-ring rather than as a slippery lubricant. The catch 22 is that the best "sealant" lube may not be the best lube in other respects -- an example being my experiment with Permatex #2 gasket sealer as a bullet "lube," working surprisingly well in a snub nose revolver but making a mess in a rifle.
2) streaks of lead near the muzzle due to the bullet actually beginning to melt due to sliding friction and/or heat from combustion gases. Whereas "peak pressure" leading is worse in the corners of the grooves, sliding friction leading may be worse on the lands. Sliding friction will be highest at the muzzle because velocity is highest at the muzzle. Also, the bullet temperature will be highest at the muzzle due to the accumulative heat absorption from both sliding friction and from the base's exposure to the hot gases. Pressure has fallen dramatically by the time the bullet reaches the muzzle, so the "sealant" qualities of the lube matter less while the lubrication qualities matter more.
A popular theory is that leading at the muzzle means the bullet was "running out of lube," but I find it easier to believe that the bullet simply got too hot. Of course those two things may be related -- if friction was high because the lube failed to reduce friction for whatever reason, the friction will create more heat! But on the whole, I have not noticed that any particular quantity or quality of lubricant is required to avoid leading at the muzzle, the lube just has to exist and it just has to possess some modest lubricating qualities.
In addition, it may be that a bullet lube acts like a "coolant." Harold Vaughn, in "Rifle Accuracy Facts," demonstrated that the carnuba wax used in conjunction with moly coating effectively cooled the hot gases because of the energy required to vaporize the wax. One can imagine that this vaporization process may create a thin layer of cooler gases at the bullet base as the molecules of lube shed by the bullet are vaporized.
3) a soft grey "wash" or mist, typically most visible near the muzzle. I believe this is lead that was vaporized by hot gases -- most likely there was some gas cutting near the peak pressure point. The vaporized lead was then carried along with the hot gases down the barrel until combustion temperatures drop enough to condense the vapor, leaving a mist or a "wash." The grey "wash" is easily removed with a wet patch.
Our understanding of cast bullets continues to evolve, and I reserve the right to change my mind, but at this moment I believe that a bullet lube is firstly an o-ring and secondly a lubricant. Too much emphasis has been placed on the lubrication qualities -- hence we have lubes with slippery ingredients like jojoba oil, castor oil, Mobil One, moly, etc. -- and not enough emphasis on the o-ring qualities, which require toughness and tackiness.
There is nothing about HVR that suggests it has exceptional lubricating qualities -- it is a hard, tough, and tacky lube, not a slippery lube -- yet it works very well. Likewise, Alox is viscous and tacky, but not particularly slippery.Lube Stars:
another popular theory is that an adequately lubricated bullet should leave a "lube star" at the muzzle, Yet HVR does not leave a lube star, so I do not believe in the "lube star" theory.Lube Purging:
another theory is that residual lube may build up in the barrel until finally a bullet comes along and pushes the residual lube out of the barrel. According to the theory, the unstable bore condition results in fliers. Well, I agree that a stable bore condition is desirable, but when I do bore scope inspections I don't detect gobs or streaks of residual lube in my barrels. In fact, it stands to reason that any residual lube would be consumed by the the hot combustion gases.
That said, I have, in certain loads in certain firearms, observed residual lube in the neck area of the chamber, though not in the barrel itself. Have you ever seen a fired case with a streak of lube on the neck? Well, I have. What happens is that as the bullet enters the throat and is engraved by the rifling, the lube that is displaced by the rifling is forced to go somewhere .... and the only place it can go is backwards, squirting lube into the neck area, and sometimes in the entrance of the throat. I suspect that happens often but that most of the time the "squirted backwards" residual lube is consumed by the hot gases, and only under certain circumstances does residual lube survive. When the next round is chambered, the residual lube may make it a tight fit, or it may push the bullet to one side causing a flier. For the most part this "lube squirting backwards as the bullet engraves" does not seem to be not a common problem,