French 75 vs German 77 characteristics Question

[MikB]

Another two-penn'orth to throw in the pot in the light of recent posts...

I reckon 18-pdr is just as much a "Calibre" as 75mm. In a debate on another forum, the most convincing post on the derivation gave an Arab word variously rendered as "Qalib" or "Khalib", meaning a shoe-mould akin to a cobbler's last and therefore kept by a tradesman in a range of sizes.

So "Calibre" is just a non-standardised ID label for a particular type of ammunition and not necessarily related to any particular dimension such bore or projectile diameter.

As anyone who has studied smallarms calibres - especially commercial ones - knows, even when the calibre name suggests such a diameter with some precision, the relationship with the actual dimensions can be very casual... Examples include .32 Auto, .38 Special, 7.62x39mm., .44 Special and Magnum, none of which use bores or bullets of the stated diameters.

So I think a 'calibre' is just an accepted name label, and applies just as well to 6-, 13- and 18-pounders as to 37, 75, 77mm. or 3-inch, 4.7-inch etc.

Some of the propellants used in 1914 ran a high flame temperature and may have had some erosive effect on barrel throats, but those used in the leading-edge guns under discussion here generally embodied the best knowledge available at the time, which was substantial. Corrosive effect was inconsiderable, if identifiably present at all. Even black powder will not produce identifiable corrosion during even a protracted firing session - though it might introduce a number of mechanical difficulties associated with the large amounts of fouling it produces .

Working only from general outward appearance, the slim, lightly constructed and highly stressed structure of the 75 looks less able to withstand very long firing sessions than the heavier build of the 18-pounder. I've no sources of my own of any empirical data showing how well these guns could keep up sustained fire, but I'm sure someone will have....

Regards,

MikB

[28juni14]

.... I'm not certain what the converted poundage of the "75" would be, but conversely, the 18pdr is a tad less than 84mm.

I failed to add earlier that the approximate 700 yds range advantage of the M1897 over the FK96n/A, was negated by the French fire policy to not exceed 5000 yds; the maximum effective reach fo their shrapnel shells. (L'Evolution de L'Artillerie pendant La Guerre)

[Hoplophile]

The standard shrapnel shells for the French '75' weighed 7.2 kilos. Allowing 2.2 pounds per kilo, this gives us a shell-weight of some 15.84 pounds. The standard high-explosive shell weighed 5.5 kilos, which is but 12.1 pounds.

As far as range goes, one must be careful of sources that compare chalk to cheese. In particular, the years before the war saw a number of German authors try to diminish the range advantage of the French 75 by comparing the 'normal' range of the 75 with the 'dug in' range of the 77. (The 'normal' range is the one attainable when the piece is standing on a flat piece of ground. The 'dug in' range is one attainable when the trail is placed in a hole, thereby allowing the barrel to achieve greater elevation.)

When both pieces used the same sort of ammunition (high-explosive shells) and neither were dug in, the French '75' had a maximum range of 6,800 metres while the German '77' had a maximum range of 5,500 metres.

Digging in the trail increased the range attainable by the French '75' considerably - to more than 9,800 metres. Doing the same for the German '77' increased the range to 7,800 metres. (I say 'more than 9,800 metres because I only have the 'dug in' range for the heavier high-explosive shell that was introduced during the war. This shell weighed as much as the shrapnel shell, to wit, 7.2 kilos.)

The only time that the German '77' had a range advantage over the French '75' was when both weapons were standing on flat surfaces and firing shrapnel shells. In such a case, the range for the German '77' was 5,500 metres while that for the French '75' was 5,000 metres. This difference, however, was a function of the limitations of the time fuzes used rather than the performance of the guns.