Low Tech cannons mortars and shells

[Pursuivant]

Originally Posted by Fred Brackin

You need to add in a "but they didn't work very well at all.".Or even an "They were more dangerous to the users than the targets".

By the 18th century, they were sufficiently reliable and effective that they were part of every artilleryman's arsenal.

You can use the HT stats for a black powder grenade as a basis for a 1 lb. shell.

After that, assume a hollow sphere with 0.375 to 1-inch thick walls depending on shell size and the rest of the volume is black powder. Model volume of powder as 4/3 PI r^3 where R is (shot diameter - (wall thickness x 2))/2. Assuming a density of 50 lbs/ft^3 for black powder you can work out explosive damage based on weight

There is general information about black powder artillery shells in GURPS 3E High Tech 3rd Edition. It says that BP shells do explosive damage based on filler weight, which is usually about 10% of total shell weight. Fragmentation damage is 2d to 12d+ cutting damage per hex within the fragmentation radius. Material picked up from a ground burst material might add 1d-4 to 1d-2 HP cutting.

I consider the GURPS 3E HT rules for shrapnel to be remarkably generous. Unless they were specifically shrapnel shells (shell filled with musket balls) cast-iron shells tended to shatter into just a few pieces. Air bursts directed shrapnel in all directions rather than just towards the ground like modern shrapnel shells. Ground bursts buried themselves in the ground so shrapnel fragments just got buried in the earth or channeled upwards with the blast.

That's not to say they weren't potentially lethal, just not "instant wound/death" as the rules imply. In particular, fuze-timing was a huge issue for pre-20th c. shells, so shells might burst before they reached the target or after they'd passed it by/buried themselves in the ground.

Battlefield archeologists/scavengers regularly collect shell fragments from the ACW and other 19th c. conflicts, which gives you a sense of relative lack of fragmentation damage.

As a SWAG, I'd suggest 1d HP pi++ damage for a low-explosive driven lead ball, 2d cut for a chunk of cast iron shell, with chance of a hit (3d) being 12 for shrapnel, 9 for shells) with normal penalties for range to hit more distant targets. A critical hit means a hit by some sort of shrapnel out to ~2x normal blast radius.

Way too much information on late 19th c. artillery here.