Home

BPCR Lube Thoughts and Findings - Dan Theodore


The topic of what a BPCR lube does and how it does it is often the topic of conversation; at matches, over the phone and online. Those of us that have shot BPCR for awhile know that accuracy degrades rapidly without a good lube as well as either wiping or blow-tubing between shots. After several years of extensive research, experimentation and thinking about BPCR lubes and how to make them better some general conclusions have been drawn.

One realization is that, from this writers perspective, the question is often answered in a manner that addresses a characteristic of appropriate BP fouling control. That question is, “What does BPCR lube do?” The typical answer is, “It keeps the fouling soft.” While that is not inaccurate, it does tend to focus the shooter on a characteristic of effective BP fouling control, not the fundamental objective. The way the question is now answered by this shooter is, “It keeps the coefficient of friction between bullet and barrel consistent shot-to-shot.” That is different than saying it keeps the fouling soft. If the fouling is soft and the same amount of moister is added by blow-tubing between shots and the barrel does not sit between shots too long in hot, dry conditions and the barrel has not become too hot, the coefficient of friction between bullet and barrel CAN be consistent. If wiping between shots is used then the condition of the bore must be the same shot-to-shot for top accuracy and consistent muzzle velocity. The further out one shoots the more consistent muzzle velocity comes into play in support of top match performance. At 100 yards excellent groups can be shot with less than consistent muzzle velocity. But at 1,000 yards that same load will string vertically to the detriment of one’s score as one will tend to correct elevation for a random occurrence, muzzle velocity variation, which will further acerbate the vertical dispersion of bullet impact.

So now that the stage has been set by stating that good BP fouling control keeps the coefficient of friction between bullet and barrel consistent shot-to-shot, the underlying phenomenon of how BPCR lubes work to accomplish this goal can be addressed.

During a focused effort lasting about 6 months just about every known lube component was tested using several measurement techniques. In the lab each lube component was heated to the smoke point and the temperature recorded. That is the temperature at which the lube component begins to break down chemically. Once this happens the lube component begins to loses its ability to perform properly. The lube components were also burned-off in a stainless steel crucible to determine the type and amount of residue remaining as that can indicate how the lube component might perform in a barrel under the high heat and pressure of firing a BPCR round. All of these results were recorded and used as a data base during lube development as well as to see if there was any correlation between these two lab tests and field tests in hot, dry conditions. The melting temperature was also recorded for any lube components that were solid at room temperature.

Each lube component was mixed 50/50 with beeswax and tested in hot, dry conditions. At the start of testing it was decided that 90 F was the lowest ambient temperature and 30% humidity the highest allowed during testing. Temperature and humidity were recorded during each testing session before each 10-shot string. By the second round of testing it was becoming apparent that harsher testing conditions were needed as it was becoming difficult to differentiate between the second generation lubes’ performance. The testing limits were changed to a minimum ambient temperature of 100 F with humidity below 20 %. Final testing the following summer was done on the 1,000-yard line with the barrel exposed to the sun in 105 F to 110 F temperatures and humidity below 15 %. The number of shots was increased to 20 to heat the barrel as much as possible to induce fouling control issues. Of course the barrel was cleaned and cooled to ambient between 20-shot strings.

The first summer of lube testing a 40-65 Browning was used. The load was 60 grains of Swiss FFFg, Fed215M primers, 60/1000” Walters wad and the 400-grain Gunn/Snover bullet cast with 20-1. The Federal 215M primers were used simply because they were not being used for anything else. For match shooting Large Pistol primers are used exclusively. Three, 4-second exhales were blown down the blow-tube and into the barrel between shots and the same was done after the barrel had been inspected at the muzzle for fouling characteristics that were recorded at the end of each 10-shot test string. After the final blow-tubing a dry, tight patch was attempted to be pushed down the barrel. Sometimes a patch would not go down the barrel at all. In those instances the barrel had completely fouled out with hard BP fouling and leading. Some formulations would allow a tight, dry patch to slide down with ease with no hard fouling or leading whatsoever.

A lube-star on the muzzle is NOT necessarily an indication that one’s lube is working. Some formulations produced very nice lube-stars on the muzzle and fouled-out barrels, while some formulations did not produce much of a lube-star but the tight, dry patch slid down the barrel with ease and a very consistent resistance at the cleaning rod handle. A very good indication that one’s lube and blow-tubing technique is working properly is when a tight, dry patch, after blow-tubing just like was done between shots, will slide down the bore with consistent, smooth effort and no friction increase from breech to muzzle. The patch should contain black, moist fouling and no lead. Certainly some rifles lead as their barrels were not finished properly or the bore was allowed to become pitted with rust. The pits and/or tool marks from manufacturing are problems that can be controlled to some extent by the use of a well developed lube. Several shooters that have always pulled lead out of their barrels between relays using the popular lubes have found that a more advanced lube, developed to do more than keep the fouling soft, completely removed their need to clean between relays in hot, dry conditions during BPCR Silhouette matches.

Typically one testing session consisted of 10 rounds each for 10 different lube formulations for a total of 100 test rounds. That was a long day of testing that typically could not start until about noon and was either finished under the proscribed conditions or terminated if the conditions deteriorated: cooled down too much or humidity increased above the test limits.

Each formulation was tested by first cooling the 40-65 Browning barrel to ambient temperature using cold water blow-tubed into and stopped in the barrel. Typically two mouths full of cold water would lower the barrel to ambient waiting about 20 seconds for the water stopped in the barrel to absorb barrel heat. Three temperature sensors were attached to the barrel to insure a “standard” barrel temperature at the start of each 10-shot string used to both test lube effectiveness as well as accuracy on a 100-yard target.

Another observation recorded along with accuracy was how many rounds it took for the load to settle down since each string was started with a clean barrel. A very consistent blow-tubing technique was used between shots and shooter hydration was maintained by continually drinking water. The barrel was cleaned before cooling and dry patched so that the barrel condition was consistent at the start of each 10-shot test string.

In excess of 30 lube components were tested in the baseline 50/50 mix with beeswax. The second phase of lube testing required that not only accuracy and fouling control were tested but also how well each formulation worked in a lubesizer as well as pan-lubing.

Some of the interesting observations were that some lube components actually kept the barrel cooler than other lube components. That is an attractive lube performance characteristic in hot conditions as potential of lube failure from barrel heating is reduced. How quickly a lube “settled-down” to produce consistent accuracy was also recorded as was mentioned above. Some lube formulations allowed the group to form after only one round down a cleaned barrel. That lube performance characteristic is beneficial for match shooting, silhouette or target rifle, as one can start to work on their elevation and windage after the first shot instead of having to shoot 2 or 3 rounds. After a number of years as a BPCR match competitor it is an obvious advantage to shoot as few sighters as possible in very hot, dry conditions to reduce barrel heating especially when the barrel is exposed to the sun. Another finding was that some lubes required far less lube to work effectively. While some lubes required 3 to 4 grains of lube to work properly the more advanced lubes required less than 1 grain. Also, some lubes left far more “fouling” in the barrel than the more efficient advanced lube formulations.

Now that the baseline BPCR lube testing has been described and some findings related the topic of how a BPCR lube works should be quite straight forward. We have heard a number of theories about how BPCR lubes work, but so far none of the theorist has produced experimental results to either confirm or refute their theories.

Back in the Fall of 1998 a few simple observations from range testing sessions shed some light on the question of how BPCR lubes work to “control” the fouling; keep the coefficient of friction between bullet and barrel consistent shot-to-shot. Those simple observations were based on collecting the first patch used to clean the barrel between strings of fire for observation in the lab. The heavily coated patches that were pushed down the barrel after blow-tubing were allowed to air dry for a few days. Then, the fouling from the patches were observed and put though some simple tests. One interesting observation was that the fouling had turned from black to white. The pH was tested, but more interesting was the fact that when the dry, white, crumbly fouling was placed in one palm while the other palm was wetted and both hands rubbed together the sensation was like washing one’s hands with soap. From there it was a little leap to the theory that we are making a crude form of soap in our barrels. Most of the residue remaining when BP is ignited is potassium carbonate, potash. Our foremothers used to make soap by collecting the hearth ashes in a pot kept next to the hearth hence the name “potash.” She also collected grease from the cooking process and with water and heat made soap. That is precisely what is happening in our BPCR barrels when we use BP. As many know soaps are excellent high-temperature, high-pressure lubricants. Lithium grease comes to mind. It is a soap. For smokeless powder the process in the barrel is quite different, lube performance requirements unlike BP lubes and not the topic of this discussion. But, the end result hoped for is the same consistent coefficient of friction between bullet and barrel shot-to-shot.

So, it would seem that to keep the coefficient of friction consistent shot-to-shot BP lube must transform a certain amount of the potassium carbonate into a crude form of soap and the appropriate amount of moisture must be added through blow-tubing. BP combustion also adds some moisture to the barrel. It could be that the combustion moisture forms the basis upon which continued shooting can take place with the addition of an appropriate level of blow-tubing moisture. Dry burning BP’s are notoriously difficult to control from a fouling management point of view. That dry burning characteristic may restrict this hypothesized initial soap formation process.

Certainly there are other mechanical and chemical processes doing on through each cycle of shooting and blow-tubing, but it is believed based on extensive testing and results interpretation that soap formation is the primary vehicle for “keeping friction consistent.”

Cheers,

DanT



December 27, 2004