Re: Low Tech cannons mortars and shells
 

I seem to recall a lot of "exploding" bullets were actually what we would now call self-fragmenting - back drilled and loaded with mercury IIRC, so that they expanded on impact.

Re: Low Tech cannons mortars and shells
 

It seems like none of the rules are great for representing these rounds (or indirect machine gun fire).

• Plain old RoF: does not let you attack everyone in an area
• Cone + Bombardment: chance that any one target is hit is always the same anywhere in the area of effect
• Suppression Fire: officially only covers a two-yard wide path
• Fragmentation: assumes spherical not conical scatter

On the balance, I think something similar to the Fragmentation rules would be best for these munitions (and this use of high-rate-of-fire weapons such as MGs or a whole battalion of bolt-action rifles), but you would want to tweak the math for weapons which scatter projectiles in a cone rather than a sphere.

Re: Low Tech cannons mortars and shells
 

It seems fairly simple to me. Draw a cone for the area potentially affected, then use the fragmentation rules as normal to determine how much shrapnel hits each person therein.

Re: Low Tech cannons mortars and shells
 

Since you know exactly how many projectiles are released, you would want to look at the actual chances of a standing human getting hit at various ranges from the point at which the projectile starts to disperse, and chose the effective skill (and range modifiers) accordingly. If one part of the GURPS rules is too simplified or unrealistic for you, its rarely a good idea to assume that a module next to it is perfect for your needs (Gell-Mann Amnesia).

We already have one person who thinks that the Fragmentation rules may be too generous for low-tech projectiles which were not scientifically designed to break into many fragments just big enough to disable.

Re: Low Tech cannons mortars and shells
 

The ones I was reading about were definitely explosive; they were intended for shooting ay caissons and other battlefield ammunition stores.

Re: Low Tech cannons mortars and shells
 

The fragmentation rules generally scale a bit wrong -- it's too likely to hit at long range, too unlikely at short range -- and using them for area fire with bullets would have the same problem.

A reasonably realistic formula for whether area fire hits targets in the area is that the hit chance is 9 + (2x SM of target) + (SM for projectiles fired) - (2x SM of area).

Re: Low Tech cannons mortars and shells
 

Of course it won't be perfect, but I would think that a simple model that produces not-obviously-crazy results is generally preferable for gaming than a more accurate model with lots of finicky details and lookup tables.

EDIT: As I understand it, if the fragmentation rules are too generous for low-tech explosive projectiles, it's simply because said projectiles produced fewer fragments than the ones GURPS is used to modeling. It should be simple enough to resolve this by reducing the base chance of a fragment hit (i.e., the effective "skill" rolled against), without needing to completely rewrite things.

Re: Low Tech cannons mortars and shells
 

Actually, for machineguns Suppression Fire is reasonable. Remember, it's a 2-yard wide line per 5-rounds per second if the gunner wants to spread the fire. In real life 'beaten zones' are filled by having several guns firing and over time.

Re: Low Tech cannons mortars and shells
 

They also understate how many fragments you'll likely get hit by when very close, and overstate how many you'll get hit by at longer distances.

Part of this is a problem with the rapid fire rules - they assume that lots of shots/fragments in the air both increases hit chances and increases the number of hits you'll take, and this is correct sometimes, but not all the time.

Re: Low Tech cannons mortars and shells
 

In general I'm not that worried about the number of hits being wrong, other than the annoyance of rolling it, because if five hits didn't take the target down it's probably impervious and twenty hits won't either.