There are 6 tests done using a patched round ball, and two tests done using the T/C Maxi-ball. A variety of patch thicknesses and lubes are used. While we can visualize the results of ever diminishing patch thickness, this writer feels additional testing should have been conducted to more definitively establish the results of different patch lubes on initial velocity.
Using the results from the table, it becomes evident that as patch thickness is reduced, velocity starts to incrementally fall off. Likewise, we can deduce that a point of equivalence is reached where the use of a thin patch is no better than using an unpatched round ball. This can only be attributed to a loss of pressure from the resultant blowby of breech gases past the patching material. This blowby has a secondary effect on the gun, that of increased breech erosion, a topic which will be covered later.
From a practical shooting standpoint, what does the chart tell us? The lubricated patch was developed concurrently with the round ball in a rifled gun and aided in the facilitation of easy loading. However, we can easily see that this combination is ballistically inefficient, resulting in a trade-off in velocity for a gain in accuracy. Yard estimates this loss as a result of blowby to be up to 20%, as opposed to a smooth bored gun shooting a minie ball.
In the case of the minie, the skirt of the projectile expands upon ignition to effectively seal the bore with minimal blowby, and a resultant increase in velocity of the projectile. Likewise, the use of a tightly patched round ball in a smoothbore will see resultant velocity gains. However, since the projectile is not stabilized by rifling, we see a resultant loss in accuracy as distance increases.
Knowledgeable target shooters will realize the positive effect of increased velocity on trajectory, and also the gains in accuracy resulting from a decrease in wind drift, due to shorter time of flight to the target. Hence, they routinely use the tightest patch/ball combination in their guns, coupled with the slickest patch lube. I find it interesting that in tests 1 and 2, that Crisco gives a higher velocity than the water and soluble oil mixture. However, these are the only comparisons we have and further testing with the same patching material and different lubes would have proved more interesting and definitive. This is too small a sample to draw any true correlations from regarding the effects of bullet lubes on velocity.
In direct contrast to the target shooter, we have the hunter who is usually more interested in the ease and speed of loading in the field. It is the hunter who should pay more attention to these results. Higher velocity means being able to maximize both greater accuracy within a longer, point blank, range zero; and greater retained energy for cleaner kills at longer ranges. Many hunters mistakenly sacrifice clean, first shot kills for the resultant follow up shot which might not be necessary. Perhaps they should re-examine their rationale.
Now let us examine the blowby which is exhibited by the patched round ball, and its relative effect on breech erosion. The following information from Jan Hamier probably best states the process:
In addition to that, combustion residues have lots of small solid particles (K2O, K2S, carbon etc.) that act as a "sandblaster" when transported as a dry aerosol by the high velocity gases blowing by.
Finally, the carbon-rich environment at high temperature tends, with hot burning (generally fast) powders like fine rifle types, to cause carbon migration into the steel of the barrel (like the principle used for KASENIT), creating a thin layer of glass-like steel, extremely hard but very brittle. As the barrel expands under pressure, that glassy steel layer cracks and sometime flakes off, creating chemical erosion on top of the abrasion and thermal erosion described earlier.
In short, for a long barrel life, one needs a good bore seal, and cold burning powder with a low excess carbon content.
I still believe that the main effect is the high velocity heat generated by the blowby, just like a small grain of crap on a valve seat quickly leads to a burned valve on an engine, at the point of the leak.
Much to do is made about the effects of chlorides on breech erosion. Some have condemned the use of Pyrodex because it contains perchlorates which will erode the breech. Other writers claimed to have sectioned barrels for examination, and found what they call "classic chloride pitting" or stress checking due to the use of certain chlorine bearing compounds, with WD-40 coming to the forefront as one of these compounds. To support these conditions, certain technical bulletins from industry are alluded to. However, we must ask ourselves, "Can we take the results of failures which occur under highly specialized circumstances and extrapolate those failures to black powder conditions?" This writer is dubious of making that transfer.
All the by-products of black powder or pyrodex combustion are water soluble. Likewise, the salts generated by percussion caps are water soluble. This makes a strong argument for using only water to clean our guns. Having done that, we further only need a simple oil, either animal, vegetable, or mineral, to arrest the rusting which will naturally occur on exposed steel surfaces. The use of exotic cleaning solutions, and experimentation with all sorts of esoteric preservatives seems totally unnecessary.
In summary, it is readily obvious to this writer that breech erosion can and will occur over time with the patched round ball. It is further obvious that breech erosion is accelerated by the carelessness or lack of understanding of a shooter who introduces the above conditions into the breech of his firearm. Clean thoroughly with water to remove all soluble salts, dry well to prevent water from being trapped in the breech area, and lubricate all metal parts with a simple oil to arrest rusting. Do not use products which have an unknown, long term effect on steel. Use the proper patching material to minimize blow by. Anything more is just courting disaster.
ęDave Kanger 1999