[Low-Tech] Chinese Guns

[Icelander]

GURPS Low-Tech p. 87-88 has the 'Crouching Tiger Gun' and the 'Long-Range-Awe-Inspiring Gun'.

I'm having some trouble reconciling the stats of these to the rules for stone balls (under 'Bombards' on LT p. 87 and that of 'Multiple Projectiles' on HT p. 172.

There's no information in Low-Tech on the caliber of the Chinese guns or the diameter of the lead shot. Going by what sources I can find on the Internet, the Long-Range-Awe-Inspiring Gun seems to have been around the caliber of a 2-lb cannon, i.e. 50mm, and the half-inch, half-ounce lead balls would be around .50 inch or 12.7mm to 13mm and 200-230 grains.

From what I can find, one common size for Chinese lead balls for multiple projectile loads seems to have been .43 caliber, which would be 11mm diameter balls weighing about 120 grains. It doesn't seem that this size is assumed in the listed stats in LT, however, as that would make the 3.5 lbs. WPS for a load with 100 lead shot too heavy, unless we are meant to assume a 1:1 correspondance between powder charge and shot weight.

The Crouching Tiger Gun has the same WPS for a load with 100 lead shot as the Long-Range-Awe-Inspiring Gun, so it seems that it would be shooting the same size lead shot, i.e. something weighing around 200 grains per shot.

Here's what I can't figure out:

1) How does the Crouching Tiger Gun get Dmg 6d+2 pi++ with a stone ball?
According to the preceding page, LT p. 87, the weapon tables take into account the halved Dmg and Range of stone balls. This implies that the damage of the Crouching Tiger Gun would be 12d+4 pi++ with a single lead ball, which is utterly awesome compared to any other 47 lbs. firearm, let alone one that costs only $650.

2) Why does the Long-Range-Awe-Inspiring Gun only have average Dmg 0.5 point higher than the Crouching Tiger Gun?
According to the Internet, the Long-Range-Awe-Inspiring Gun fires a 2-lb lead ball with an 8 oz. powder charage. Even if that's inaccurate, the WPS is 3 lbs., so it's reasonable to assume a 14,000-17,500 grain lead ball and 3,500-7,000 grains (8-16 oz.) of propellant. The listed Max Range is 1,200 yards.

The Crouching Tiger Gun has WPS of 1.15 lbs. That means a weight of less than a pound for the stone ball, even if the gun were only loaded with the 3 oz. of powder that a quick Internet search suggests for it. I actually can't find any mention of stone balls for the Crouching Tiger Gun (all I can find are for older guns), so I don't know the specific weight, but with this WPS, it can't be heavier than 1-lb.

How does a lead ball of 2-lb or more, travelling fast enough to reach 1,200 yards, not penetrate better than a stone shot that weighs less than a pound, which doesn't reach more than 550 yards?

Also, how does this fit in with the halved Dmg for stone balls from LT p. 87?

3) How do the 13mm lead shot get Range 130/1,200?
According to HT p. 172-173, 'Canister (TL4)' gets 1/2D Range is (diameter of bullets in mm) x5 and Max Range (diameter of bullets in mm) x50. To get 1/2D 130, the diameter of the lead shot would have to be 26mm. On the other hand, the 'Multiple Projectile' rules on HT p. 172 state that number of projectiles (NP) cannot exceed (weapon's caliber/projectle diameter), so in order to fire 100 lead shot of 26mm, the Long-Range-Awe-Inspiring Gun would have to have a caliber of over 120mm.* Also, 100 lead shot with a 26mm diameter would weigh over 20 lbs., while the WPS is only 3.5 lbs.**

4) How is the Dmg for the lead shot figured?
Using the 0.10 NS modifier for 100 projectiles from the table on HT p. 172, I can't get Dmg 1d-1 pi+ for either the Crouching Tiger Gun or the Long-Range-Awe-Inspiring Gun.

If I simply multiply the NS by the damage for a stone ball in the Crouching Tiger Gun, I get 2.3 (6d+2=23; 23*0.10=2.3). Follow the rules on 'Adjusting Damage' on HT p. 166, that comes out to 0.657 die or Dmg 1d-2. But since these are lead shot, I probably shouldn't be using the halved Dmg from a stone ball as the basis. Doubling the Damage for using lead ammunition comes to avg. Damage 4.6, 1.314 dice or Dmg 1d.

Multiplying the Damage of the Long-Range-Awe-Inspiring Gun with the NS 0.10 yields avg Damage 2.35 (7d-1=23.5; 23.5*0.10=2.35), which comes to 0.671 die or Dmg 1d-2.

*Which it clearly doesn't, both according to the sources on the weapon and common sense, in that's larger than the bore of a 12-lb cannon and the weapon weighs only 160 lbs.
**Which is consistent with around 8 oz. of powder and 100 lead shot of around 12.7mm-13mm and 200-230 grains, with an exact calculation assuming that powder charge yielding 210 grains per shot.

[Icelander]

Can some of these discrepancies be explained by the status of these guns as Bombards?

If so, what assumptions are it that differ some materially from the underlying assumptions of the rules for other guns?

In any case, pictures I can find of these Chinese Guns do not appear to rule out using them for direct fire. Should these stats apply to direct fire as well?

[The_Ryujin]

Hmmmm, never paid attention to the firearm stats in Low-tech before. I'll take a hard look at them when I get some free time (which probably won't be till Friday). Though I have to wonder if they used David and Han's gun design system for stating them.

[Fred Brackin]

Originally Posted by The_Ryujin

Hmmmm, never paid attention to the firearm stats in Low-tech before. .

Except for the P class errors I've mostly noted them in my head as "don't work well enough to be worth the effort of carrying around".

Any eccentricities of performance could be explained by inefficient design (i.e. the makers didn't know any better) unless they work too well which could be explained by a game designer trying to make them even marginally useful.

Even if these things existed in a setting I was GM'ing what I'd tell player whose character saw one demonstrated was that they appeared to be less useful than large firecrackers.

[The_Ryujin]

Originally Posted by Fred Brackin

Except for the P class errors I've mostly noted them in my head as "don't work well enough to be worth the effort of carrying around".

Any eccentricities of performance could be explained by inefficient design (i.e. the makers didn't know any better) unless they work too well which could be explained by a game designer trying to make them even marginally useful.

Even if these things existed in a setting I was GM'ing what I'd tell player whose character saw one demonstrated was that they appeared to be less useful than large firecrackers.

I'm thinking you're right here. I did some quick number running and found it hard to get 6d+2 worth of damage for the crouching tiger cannon without bumping the muzzle velocity up to almost 1,000m/s! And that's before halving the damage!

Now my damage formula is still incomplete so there is a chance I might be missing something but given that it has come within 20%-30% of most of the damage GURPS assigns guns so far I still think something is off. I'd peg it as doing maybe 3d+1 at most if you ignore the halving.

[whswhs]

Originally Posted by The_Ryujin

Hmmmm, never paid attention to the firearm stats in Low-tech before. I'll take a hard look at them when I get some free time (which probably won't be till Friday). Though I have to wonder if they used David and Han's gun design system for stating them.

I did in fact use David's system for every gun in Low-Tech. Unfortunately, my design notes are no longer with me, after two moves, one to a different city. I do have a draft version of David's system on my hard drive, but I would have to review it—and that's not going to happen now, as I have work deadlines staring at me.

[The_Ryujin]

Originally Posted by whswhs

I did in fact use David's system for every gun in Low-Tech. Unfortunately, my design notes are no longer with me, after two moves, one to a different city. I do have a draft version of David's system on my hard drive, but I would have to review it—and that's not going to happen now, as I have work deadlines staring at me.

Oh, I didn't now you did the gun stats in Low-Tech. Learn something new every day heh.

Ok, since you used David and Han's system that means there must be a factor I'm missing from my reverse engineering of the damage formula. Just knowing this on it's own is helpful.

But yeah, go handle your work. If you do have time at a later date to look over things that would be cool but I personally trust your judgment so it must be something that we're overlooking.

[Icelander]

Originally Posted by The_Ryujin

I'm thinking you're right here. I did some quick number running and found it hard to get 6d+2 worth of damage for the crouching tiger cannon without bumping the muzzle velocity up to almost 1,000m/s! And that's before halving the damage!

Now my damage formula is still incomplete so there is a chance I might be missing something but given that it has come within 20%-30% of most of the damage GURPS assigns guns so far I still think something is off. I'd peg it as doing maybe 3d+1 at most if you ignore the halving.

The halving noted on LT p. 172 is presumably meant to account for the lower density and thus the much lower mass of the projectile than if it were lead. I'm pretty sure that you shouldn't apply it if you're calculating the damage using an equation which already accounts for velocity, mass and the diameter of the impact surface, such as Douglas Cole's Ballistics spreadsheet.

Of course, a velocity approaching 3,000 fps from a black powder weapon is extremely unlikely. The highest I've heard for a black powder weapon is 2,400 fps and that was a modern weapon expressedly designed to maximise velocity with black powder, hence unlikely to be achievable at early TL4. For one thing, the velocity of the exploding gasses in most black powder mixtures actually used for historical weapons at the time seems not to have exceeded 2,000 fps very much.

The highest muzzle velocity I've heard argued for period pieces at TL3-4, that is before what GURPS calls TL5, would be 1,500-1,600 fps and even then, that would be exceptional indeed, if it's indeed true that such velocities could even be achieved without TL5+ chemistry. Most black powder weapons were subsonic and those that weren't do not seem to have much exceeded 1,200 fps at TL4 and 1,700 fps at TL5.

I would not be surprised if the Dmg 6d+2 pi++ is a mistake, in that it fails to account for the effects of a stone ball. Dmg 3d+1 pi++ is much more probable and more in line with other black powder weapons.

[The_Ryujin]

Originally Posted by Icelander

The halving noted on LT p. 172 is presumably meant to account for the lower density and thus the lower much lower mass of the projectile than if it were lead. I'm pretty sure that you shouldn't apply it if you're calculating the damage using an equation which already accounts for velocity, mass and the diameter of the impact surface, such as Douglas Cole's Ballistics spreadsheet.

Of course, a velocity approaching 3,000 fps from a black powder weapon is extremely unlikely. The highest I've heard for a black powder weapon is 2,400 fps and that was a modern weapon expressedly designed to maximise velocity with black powder, hence unlikely to be achievable at early TL4. For one thing, the velocity of the exploding gasses in most black powder mixtures actually used for historical weapons at the time seems not to have exceeded 2,000 fps very much.

The highest muzzle velocity I've heard argued for period pieces at TL3-4, that is before what GURPS calls TL5, would be 1,500-1,600 fps and even then, that would be exceptional indeed, if it's indeed true that such velocities could even be achieved without TL5+ chemistry. Most black powder weapons were subsonic and those that weren't do not seem to have much exceeded 1,200 fps at TL4 and 1,700 fps at TL5.

I would not be surprised if the Dmg 6d+2 pi++ is a mistake, in that it fails to account for the effects of a stone ball. Dmg 3d+1 pi++ is much more probable and more in line with other black powder weapons.

Ah, then the 3d+2 pi++ (the 3d+1 was a typo) seems about right since my current model takes density into account.

[Icelander]

Originally Posted by The_Ryujin

Ah, then the 3d+2 pi++ (the 3d+1 was a typo) seems about right since my current model takes density into account.

What is the weight of projectile and velocity that you are assuming for that Dmg? And what is the caliber of the ball?