[Low-Tech] Chinese Guns

[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.

[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?

[The_Ryujin]

Originally Posted by Icelander

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

Since it's an iron ball that weights 0.52kg that gives us a roughly 25mm diameter given that iron is about 7.8g/cc.

200m/s was the velocity I used to get 3d+2. That is a bit too high for my taste but if we assume that figure in the book was correct for a normal density bullet and they forget to half it then I suppose it works, in so far as my model is right in the first place.

Hopefully we'll be able to find source that covers how fast it's muzzle velocity was to get more concrete data.

[Icelander]

Originally Posted by The_Ryujin

Since it's an iron ball that weights 0.52kg that gives us a roughly 25mm diameter given that iron is about 7.8g/cc.

200m/s was the velocity I used to get 3d+2. That is a bit too high for my taste but if we assume that figure in the book was correct for a normal density bullet and they forget to half it then I suppose it works, in so far as my model is right in the first place.

Hopefully we'll be able to find source that covers how fast it's muzzle velocity was to get more concrete data.

The Crouching Tiger Gun is supposed to have a WPS (Weight Per Shot) of 1.15 lbs., which is the combined weight of the propellant and the stone shot. I don't know what kind of stone, though I've seen sources on Turkish guns mention marble balls. In any event, it must be a tolerably dense stone, but not so dense that it cannot be worked into a round shape without unreasonble effort.

Marble has about a third of the density of iron or 2.563g/cc, so there's a benchmark you could use. Granite at 2.75g/cc makes fairly little difference. Basalt, at 3.011g/cc would be noticably denser and mean a slightly smaller ball.

I would be hesistant to use a 25mm caliber, as it would be rather difficult to fit 100 lead shot of .43 inc to .50 inch there. In fact, it would be entirely against the rules in HT p. 172 for multiple projectiles. Even if we were to assume the smallest .43 caliber shot (which would contradict the WPS as well as Range), we still could not fit more than 12 and that only with great good will and some minor frowardness at rounding.

In any case, there is absolutely no way that the projectile could weigh 0.52 kg, as that would mean that there were less than 25 grains of black powder propelling it. A more plausible powder charge would be the 3 oz. (1312.5 grains) charge that unidentified people on the Internet attribte to the Crouching Tiger Gun by citation to a 1994 volume of Joseph Needham I can't access or the massive 8 oz. (1/2 pound = 3,500 grains) charge that Joseph Needhams assigns* it in his 1987 volume I can read.

This would leave 4,550-6,737.5 grains for the possible weight of the round stone ball or 0.65-lb to 0.96-lb in GURPS terminology, 0.295 kg to 0.435 kg in civilised units.

With marble, that gives me a caliber of some 60.5mm to 68.7mm, depending on the powder charge. The lower bound of this caliber range also fits exactly with the rules on HT p. 172 used to calculate the maximum number of multiple projectiles or the cube of (barrel diameter/shot diameter).

Granite and basalt have a similar range, going roughly 59mm to 67mm and 57.5-65mm respectively, depending on how much of the 1.15 lbs. load is stone and how much is powder.

Personally, I should be inclined to estimate that a lower powder charge would be used with stone shot than lead and thefore essay the 3 oz. charge with the stones and save the 8 oz. one for the lead shot. Depending on the type of stone, I should then have a projectile which took the form of a 0.435 kg stone with a diameter of some 65mm to 68.5mm. If we want to go with the same 8 oz. powder charge for both stones and lead shot, we'd get a 0.297 kg stone ball with a diameter around 57mm to 60.5mm.

If we want 6d+2 pi++ with either load, we have to accelerate it to between 730 fps and 870 fps, depending on our assumptions for stone type and amount of propellant. This is not impossible, to be sure. With a heavy load and good powder, black powder weapons achieved this and much faster velocities too. And even the 'light' load of 3 oz. of black powder is more than three times the heavy load of a 4-bore elephant rifle.*

The mystery then becomes why the Long-Range-Awe-Inspiring Gun, with a 2-lb to 2.5-lb lead ball of diameter from 54mm to 58mm, cannot get more than a 2.2% improvement over this damage. This will occur if we can keep the velocity under 500 fps, I believe, but as to why 8 oz. of black powder should not answer for more velocity gain than that in a 3' barrel compared to a 2' one (especially if we are assuming a 3 oz. charge in the smaller gun), I must admit perplexity.

Also, if the Crouching Tiger Gun can handle that weight of shot and blazing velocity, why build a gun with an identical role and little to no improvement that's 33% longer, more than 240% heavier and almost 240% more expensive?

*With no doubt correct translation, but yet I shudder to think of a 47 lbs. gun firing almost three pound of lead shot with a half pound powder charge and question why where would be any need for the more strongly built Long-Range-Awe-Inspiring Gun if this heavy charge were not considered somewhat over-reaching for the smaller gun.
**Albeit early TL4 powder vs. mature TL5, so that the relative TNT equivalnt measured after correcting for REF might merely be as little as 2 to 1 in favour of the bombard.