Sunday, 19 May 2013

The diameter of English and French Iron Shot

I found this information about the weight and diameter of English and French iron shot in one of the books that I bought in the Caribbean, and thought that it might be of interest to some of my regular blog readers.

English and French iron shot of the same weight were of different diameters. For each weight of shot listed, the English diameter is shown first and the French is shown second (i.e. English/French).
  • 1 pound: 1.92 inches/2.01 inches
  • 2 pounds: 2.42 inches/2.53 inches
  • 3 pounds: 2.77 inches/2.90 inches
  • 4 pounds: 3.05 inches/3.19 inches
  • 5 pounds: 3.28 inches/3.44 inches
  • 6 pounds: 3.49 inches/3.66 inches
  • 7 pounds: 3.67 inches/3.85 inches
  • 8 pounds: 3.84 inches/4.02 inches
  • 9 pounds: 4.00 inches/4.18 inches
  • 10 pounds: 4.14 inches/4.33 inches
  • 11 pounds: 4.27 inches/4.47 inches
  • 12 pounds: 4.40 inches/4.60 inches
  • 13 pounds: 4.52 inches/4.73 inches
  • 14 pounds: 4.63 inches/4.85 inches
  • 15 pounds: 4.78 inches/4.96 inches
  • 16 pounds: 4.84 inches/5.07 inches
  • 17 pounds: 4.94 inches/5.17 inches
  • 18 pounds: 5.04 inches/5.27 inches
  • 19 pounds: 5.13 inches/5.37 inches
  • 20 pounds: 5.22 inches/5.46 inches
  • 21 pounds: 5.30 inches/5.55 inches
  • 22 pounds: 5.38 inches/5.64 inches
  • 23 pounds: 5.40 inches/5.72 inches
  • 24 pounds: 5.54 inches/5.80 inches
  • 25 pounds: 5.63 inches/5.88 inches
  • 26 pounds: 5.69 inches/5.96 inches
  • 27 pounds: 5.76 inches/6.04 inches
  • 28 pounds: 5.83 inches/6.11 inches
  • 29 pounds: 5.90 inches/6.18 inches
  • 30 pounds: 5.97 inches/6.25 inches
  • 31 pounds: 6.04 inches/6.32 inches
  • 32 pounds: 6.10 inches/6.39 inches
  • 33 pounds: 6.16 inches/6.45 inches
  • 34 pounds: 6.23 inches/6.52 inches
  • 35 pounds: 6.29 inches/6.58 inches
  • 36 pounds: 6.35 inches/6.64 inches
  • 37 pounds: 6.40 inches/6.70 inches
  • 38 pounds: 6.46 inches/6.76 inches
  • 39 pounds: 6.52 inches/6.82 inches
  • 40 pounds: 6.57 inches/6.88 inches
  • 41 pounds: 6.63 inches/6.94 inches
  • 42 pounds: 6.68 inches/6.99 inches
  • 43 pounds: 6.73 inches/7.05 inches
  • 44 pounds: 6.78 inches/7.10 inches
  • 45 pounds: 6.84 inches/7.16 inches
  • 46 pounds: 6.89 inches/7.24 inches
  • 47 pounds: 6.94 inches/7.26 inches
  • 48 pounds: 6.98 inches/7.31 inches
  • 49 pounds: 7.03 inches/7.36 inches
  • 50 pounds: 7.08 inches/7.42 inches
Note: The most common cannon shot used by the English are shown in BOLD.


  1. One has to wonder if this was due to the French bores being more finely cut and the casting of projectiles being more uniform. Having a bigger gap in the bore to projectile allowed for faster loading, but affecting accuracy. An interesting article follows: and and

  2. CoastConFan,

    I am not sure why there is a difference, although I doubt that the French were any better at boring gun barrels or casting projectiles than the British were. Perhaps the difference arises from the use of the 'pound' as a measure of weight, as the English pound was not quite the same as the French 'pound' or livre.

    All the best,


  3. That last remark on re the difference between 'pound' and 'livre' I hadn't thought of, having supposed the French weights had been converted to British in the above table.

    If the weights were converted, it might suggest something about the metallurgical processes that gave the British a slightly denser iron - perhaps with fewer impurities. The French there might have taken the view that as these things were to be fired off into the blue, there was little point in being over nice about purity of the metal. The Brits, on the other hand, might have seen some saving in the casting of the gun barrel, given a denser projectile, or perhaps certain advantages in accuracy with a narrower bore.

    That is supposing, of course, that the ball closely fitted the bore. Maybe the French simply allowed a greater windage in the ordnance. There might have been some advantage in the longevity of the ordnance in doing so.

    Interesting question to ponder.

  4. From

    "The livre poids de marc or livre de Paris was equivalent to about 489.5 grams (7,555 gr) and was used between the 1350s and the late 18th century"

    This would make a French pound equal to 1.0782 British pounds for this period.

  5. Archduke Piccolo,

    During my researches, I have also discovered that even within the UK there were different 'pounds' in use at various times! (The Mercantile, Tower, and London 'pounds' as well as the Imperial pound. The latter was the one used for artillery.)

    Perhaps the differences were due to the purity of the metal being used or that the French were less precise when it came to ensuring that the balls were a close fit (i.e. they were not worried about the wind age). A third option might be that the French produced artillery that could use captured ammunition, whereas the British did not. (The Russians certainly did this with mortar shells during the Cold War ... and it is not beyond the realms of possibility that the French did something similar.)

    All the best,


  6. Nigel,

    I have not done the necessary arithmetic, but that sounds as if it could easily account for the difference between British and French shot sizes.

    All the best,


  7. Near the beginning of James' naval history of Revolutionary/Napoleonic Wars their is a table showing the different 'pounds' in use by all the European powers. This has appeared in other reference works (Can't access mine at the moment due to ongoing decorating)but from memory the Danish was particularly large.

    Accounts of the period can get confusing if there is uncertainty as to whether an author is using the original designations or their own equivalents. It gets worse when discussing captured weapons re-used.

  8. Nigel,

    That comparison table sounds interesting ... and if I can find a copy I will write a blog entry about it. I am sure that other readers will find it of interest.

    This is an area where confusion about which 'pound' is being used could easily lead to even great confusion when comparisons between different national artillery systems are being made.

    All the best,


  9. The pre-revolution French pouce was 1.066" according to wiki.

    I've found the James volume and will copy the relevant pages. He notes that French shot is usually an ounce or two overweight, so perhaps add poor quality control to the confusion!

  10. Bob,
    You've been Tangoed! (on TMP)

  11. Nigel Drury,

    Thanks very much for all that information ... and I look forward to seeing the data table.

    All the best,


  12. Mike,

    That would explain the sudden increase in visitor numbers yesterday!

    It is not the first time I have been 'Tangoed' on TMP ... and I suspect that it will not be the last!

    All the best,