Many thanks Liste.
You are as always much analytic in your explanations.
However I must say you set new elements in this discussion for which there are no (I don't have) any information from hystorical Gr texts I've read nor for the total Carron's products to rely on.
These are the comertial for merchant use (special or by order I guess) carronade and the gunnade.
And although I accept any simple description for the weapon from a ordinary sailor of that time, or from an with less knowledge historian, I don't know how to see this description from an English naval officer, who, I point out again, writes about gunnery results without ful information about the gun or its nationality.
In any case, I really thank you all for this discussion which was much enlightening, at least to conclude that I can make only guesses.
Thanasis