In this fourteenth installment of Personal Defense Weapon Calibers, we’ll be looking at a highly minimalist incarnation of the PDW/SMG round: The 7.65x20mm French Longue. The story of the French Longue begins with the US entry to World War I and the brilliant inventors John D. Pedersen and John Moses Browning. Faced with the stalemate of trench warfare, these designers were tasked with finding a solution in the form of handheld autoloading weapons. Both came up with semiautomatic rifles firing small, low recoil .30 caliber rounds. Pedersen’s “Device” converted a standard M1903 rifle into a rapid fire semiautomatic, but it was Browning’s autoloading rifle and its .30-18 round (very similar to the .30 Pedersen used with the “Device”) which caught the eye of the French Ordnance officials. The .30-18 Browning, as it is called, was evidently cloned to become the 7.65x20mm Longue used with the interwar French Mle. 1935 pistols and MAS-38 submachine gun.
The 7.65 Longue was a fairly modest round, being in approximately the same class as the 7.65 Parabellum and 8mm Roth-Steyr, but more powerful than the .32 ACP. The resulting round fired a 77gr (5 gram) bullet at a muzzle velocity of about 350 m/s (1,148 ft/s) from the handgun, and 380 m/s (1,246 ft/s) from the longer barreled submachine gun. Its ballistics are given below:
Judging by the graphs “minimalist” may be a nice way of saying “woefully impotent”; the 7.65 Longue has the worst velocity, energy, and drop characteristics of all the rounds it is compared to here. However, it is notable that beyond 200m even it retains more energy than the high velocity 5.7mm round, illustrating the deleterious effect that high muzzle velocity has on such low energy rounds over moderate distances. In trade for its lackluster performance, though, the 7.65 Longue is at least quite light, at 8.6-8.7 grams per shot, compared to 12.6 grams for 9mm M882 and 20.9 grams for .45 ACP.
Still, the 7.65 Longue was at least briefly considered adequate for its intended purposes, and submachine guns in this caliber continued to be used by the French Army into the 1960s when they were finally completely phased out in favor of higher performing 9mm weapons like the MAT-49. Although automatic machine pistols have been made in smaller calibers, those weapons were not really intended to be used at ranges above more than a few meters, no different than semiautomatic pistols in that respect. In this way, I suppose we can consider the 7.65mm Longue “the smallest practical submachine gun round”.