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Windage is generally taken to be the difference between the diameters of bore and projectile. Some windage was necessary in SBML guns to avoid dangerous shot start pressures and to enable loading to be easily carried out against accumulation of fouling from poor powder, but excessive windage caused inaccuracy as well as loss of MV. The spherical projectile bounced its way along the bore, the final bounce at the muzzle determining its direction and angle of departure, both of which varied with each round! Once again, for want of any guide, windage was at first arbitrarily set at a quarter inch (6.35 mm) for all natures, an amount still in vogue in the 17th century. Gunners who realised the amount was excessive tried to have it reduced, and quoted the superior performance of the French guns in which the windage was 20% less. However, they were opposed by authorities who ruled that windage must exceed the thickness of the loaders' ladles in order that the gun might be unloaded. When Gunners pointed out that on the rare occasion a gun was found loaded at the end of a practice it might instead be cleared by firing the authorities were outraged. How dare such waste be perpetrated merely for the sake of accuracy! Another excuse for not reducing windage was the liberal tolerances allowed in manufacture not only of bore diameter but also of shot diameter, eg if the bore ended up at the lower figure and the shot at the higher, the powers-that-be argued that windage might be reduced to a dangerous level.
John Muller, in his Treatise of Artillery, 1757, recommended windage be no more than one twenty-fourth the shot diameter, but no one took any notice of him. As the years rolled by, common sense eventually prevailed until by 1828 windage had been reduced to one thirtieth the shot diameter, or less in some cases. Records indicate that while no great increase in range resulted, a significant improvement in accuracy took place.
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WL Ruffell Issue 88 December 1995 |
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