10MM - 9MM - 8MM ..??

The 10mm Auto cartridge (10x25 mm - introduced 1983) was designed to improve on the shortcomings of the .45"ACP and it is widely recognized as a powerful & effective round for auto-pistols. - Indeed some shooters and manufacturers have found it to be 'more gun' than they'd choose to deal with long term.

.. this 'excessive' power level directly led to the development by Smith & Wesson of the .40" S&W "Short and Weak" . - Funny thing is that I find the full power 10mm more pleasant to shoot than the smaller "snappy" .40" S&W is - in a 9mm sized handgun.

10 MM    To    9 MM.

The 9mm NATO cartridge (9x19 mm - introduced 1902) also named 9 mm Luger or Parabellum is generally accepted by Military & Law Enforcement - civilian shooters too, as a "Goldilocks" round that has a satisfactory power level and performance - while being a compact package with moderate felt recoil in a full-size pistol.

.. Certainly there is ongoing criticism from some that the "nine" is under-powered for the job .. but I think that's strange as it has power and velocities in a similar level to the .38" Special revolver round - that has since 1898 been lauded as an ideal self-defense cartridge in a dependable wheel-gun.

'8MM'   To   9MM.

Then I come to the 8mm - or as it's usually known .. .32"ACP or 7.65x17 mm Browning. (introduced in 1899).
- I'll explain .. If you 'google' what is 8mm in inches? .. the answer should pop-up as 8.0 millimeters = 0.31496063 inches  - And you all know that the 'thirtytwos' use bullets that mike-up between .312 - .314 inches eh .. That's 8 millimeters in American or any other language.

.. Just WHY these 8mms are variously addressed as 7.62's - 7.65's - and "thirty-twos" is as far beyond proper explanation as is f*m#n#ne logic (did I actually dare to write that? .. it just slipped out - I'm so sorry eh).

 I don't want to go overboard here about .32" Auto but will point you at my earlier rave:

https://flicense.blogspot.com/2018/09/32-acp-32-rimmed-mighty-mouse-guns.html

The "8mm" Thirty-twos certainly are not powerhouses* - but this group of center fire cartridges goes way back to the late 1800's as a popular easy shooting round that was widely used in police issue side arms .. indeed it is this long history of use in the now ancient original break-action revolvers and autos that has made it's "mouse-gun" image worse - because cautious US ammunition makers deliberately under charge & down-power their 32 S&W and Auto offerings - so as to avoid blow-ups in antique arms.

* This is not to mention the 327 Fed Mag - a sweet-shooting "8mm" revolver round that is pushing 357" Magnum power levels.

The caliber size gap between the 10mm Auto to 9mm in olde english is around 45 thou. while the "8mm" is only another 40 thousands of an inch smaller - this indicates that the powder load and pressures are more significant than mere sizes.

- If one drops down to the 7 mm step there are plenty of popular rifle cartridges to choose there - but not many handgun rounds other than 7x20 mm Japanese Nambu.
- and it gets real messy up around 11MM which is close to the .44"s (11 millimeters = 0.433070866 inches) (44 Magnum = .429") - but the many .45"s come in as 11.5MM.

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Here's a silly idea ... If I were a capital rich manufacturer aware of the sales potential for 'carry' self-defense sized handguns - I might well make a case for designing an up-powered modern 8x20 Auto rimless cartridge and slim-line auto-pistol - that while feeding and firing reliably in maybe a fixed barrel arm, would have "power" levels close-up behind the nines .. but guns so chambered as to be able to retro-fire the well established common-and-garden old .32"ACP (7.65x17mm) cartridge

 .. Something like Federal & Ruger did with the 327 Fed. Mag that also accepts the earlier shorter rimmed '32's. - I'm thinking of a powerful '8MM Auto(32)' cartridge built like a '327' cut down to 20 mm case length and rimless .. rated at a similar high internal pressure limit.

Rod says .. Hi Marty

The French 7.65x19.8 MAS is about ideal for your idea but needs to be uploaded to give a better power level.  As it was loaded (85 grain @ 1120 fps) it was only marginally better than the 7.65 Browning.  85 -95 grains @ 1200 fps would be quite effective and could fit into a very slim single-stack 4” barreled pistol, something about the size of the old Colt M1903 Pocket and Browning M1910 pistols. Cheers

That's the  7.65×20mm Longue (also known as 7.65mm French Longue, 7.65 mm Long, 7.65mm MAS, 7.65×20mm, 7.65L and .30-18 Auto for use in the Pedersen Device) - it was a straight, rimless cartridge used in the French Modèle 1935 pistol, as well as the MAS-38 submachine gun. - Case length was 19.7mm.(or 19.8)

Marty K.