Low Tech cannons mortars and shells

[Varyon]

Originally Posted by Pursuivant

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.

LE also shows up in 4e HT, on page 169. It notes they first showed up in the late 15th century, but didn't become common until the early 19th. It gives a value of 15% shell weight being explosive filler (black powder); it notes there is fragmentation involved, but as is the general rule for generic explosive shells in HT, it doesn't give any inkling of how much fragmentation is appropriate. I use a general rule of thumb that you can give up 1d of cr ex for 2d of fragmentation (to a maximum of fragmentation equal to the explosive damage), with the exact amount basically determined by whoever designed the shell. At low TL's, I don't think fragmentation is properly understood, so it might have a maximum of 1/2 the explosive damage, and I'd probably treat shells that aren't designed with any specific amount of fragmentation in mind as having 10% to 20% of the explosive damage in fragmentation (to be clear, this means a nominally 10d cr ex shell would typically max out at 6d+2 [6d+2] cr ex, at low TL's would max out at 8d [4d] cr ex, and if not specifically designed with fragmentation in mind would probably be around 9d+1 [1d+2] cr ex. This isn't necessarily realistic (it's based on the performance of the Diehl fragmentation sleeve, which is rather different from typical fragmentation), but at least it allows one to make explosive rounds that didn't exist historically (or at least aren't statted up anywhere)...