Want to buy this Luger

[Ron Wood]

Originally Posted by Michael Zeleny

How then would you explain the 8mm upper limit that he placed on the caliber that his 1899 design would chamber?

You may have glossed over my parenthetical "in its current configuration"? Luger was discussing alternative calibers with the Swiss but working within the constraints of the 7,65mm cartridge for which the Luger was initially engineered. To increase the cartridge diameter or length would require a total revamping of the firearm's component parts, both in terms of length and width of the action and the geometry of the toggle/breechblock assembly. This would have no doubt taken the Luger out of contention for the Swiss contract or at best delayed the award. Fortunately, the Swiss opted for the Luger as initially offered with a few mechanical design improvements but no change in caliber.

Obviously, when Luger did increase the caliber, he went the route of making the existing 7.65mm cartridge into a straight-sided case, engineering the projectile, powder charge and overall length of the cartridge into a round that maximized the potential of the firearm while maintaining the envelope of the original pistol action. And the rest, as they say, is history.

I am unpersuaded that all effective engineering design of a toggle action ended at the bottleneck cartridge. I see nothing intrinsic in that action that requires a specific cartridge. Chambering is a function of the design of the chamber and the ability of the action to place a cartridge in that chamber, a cyclical mechanical process that a toggle action performs quite well (Winchester and Maxim seemed not to have a problem with it).

The disavowing of a tapered round as inherently unreliable is not sound from an engineering standpoint. There are a number of calibers other than the 9mm Parabellum that have straight, or slightly tapered, cartridge. Attaining headspace requirements using the cartridge mouth is not uncommon and Luger further enhanced the required obturation with his patented stepped chamber design. Granted this enhancement was abandoned in later years as improved metallurgy, propellant charges and action dynamics rendered it superfluous, but bear in mind that the 9mm Parabellum was a ground breaking cartridge. It was the first straight cased cartridge developed for a locked breech pistol. The engineering that went into its design was masterful and its function an unquestionable success.

I am confused by your statement that “…in 1902, some Lugers were meant by their various makers to chamber some 9mm rounds”. I can agree with some Lugers, as there were indeed two variants, 7.65mm and 9mm, but I am dumbfounded that there were "various" makers! (Who other than DWM?) I may also allow that you could refer to some 9mm rounds as there appears to be vague evidence that there was a short lived experimental Borchardt bottleneck 9mm cartridge that may have figured into the initial development of the 9mm Parabellum round, but there is no documentary evidence or surviving examples.