Recently, that is until re-reading Richard Brooke's Solferino 1859 book. Therein he mentioned the French pieces de quartre fired a 4kg shell. A 4 kg shell rather than a 4 pound shell? Maybe there was some confusion? Providing even more confusion was Luigi Casali's, The Second Italian War of Independence listing the French as having 37 batteries of 4 inch rifled muzzle loading guns. Even Dr. Stephen Summerfield's recent The Italian Campaign of 1859 describes the French as having a 4 pound rifled muzzle loading gun. Pounds, kilograms, and inches all given as units of measure for the French pieces de quartre. What is going on? Many game rules also list a French 4 pounder as the dominate gun platform. Bruce Weigle in his excellent 1859 rulebook lists the French as having a 4 pounder but later clarifies that it, indeed, fired a 4 kg shell.
After investigation into this seeming anomaly, evidence points to the French Canon de Campagne de 4 - Modèle 1858 La Hitte as firing a 4 kg conical shell. Actually the weight of the projectile is listed as 3.7 kg. Could the confusion stem from the caliber or bore of the gun? Firing solid shot, this caliber tube fired a 4 pound projectile. With the introduction of rifling and conical shells, the weight of the projectile could almost be doubled. Thus a "four pound" gun firing a four pound shot could now fire a four kg elongated shell. Even though that same bore could now fire a four kg projectile, perhaps the old nomenclature was hard to drive out. Or, like the French name of the gun, itself, no mention to the unit of measure was made. The gun was simply the Canon de Campagne de 4 - Modèle 1858 La Hitte.