Tank vs. Cannon

[The Colonel]

Bit of a sanity check - is it reasonable for a low grade, early WW2 tank (say, a Japanese I-Go) to be successfully killed by a Napoleonic style cannon, possibly scared up by some Chinese soldiers?

Hi-tech gives the Bourges Mle 1853 12lber (presumably a pretty typical Napoleonic style field gun) a damage of 6dx5 (mean 105) and the FT-17 45/20 dr (and given that the FT-17 has, according to Wikipedia 8-22mm of armour against the I-Go's 6-17mm that should be representative) … which makes it look doable, but is it sane?

[malloyd]

Originally Posted by The Colonel

Hi-tech gives the Bourges Mle 1853 12lber (presumably a pretty typical Napoleonic style field gun) a damage of 6dx5 (mean 105) and the FT-17 45/20 dr (and given that the FT-17 has, according to Wikipedia 8-22mm of armour against the I-Go's 6-17mm that should be representative) … which makes it look doable, but is it sane?

I expect it is. That cannon ball has 2 to 5 times the muzzle energy of anti-tank rifles that continued in service up into the 1950s. Admittedly it's also got like 5 times the caliber, and isn't as pointy so the pressure at the point of impact is presumably not as great, but it's certainly not hopelessly outclassed. Mind you a single solid shot has to get really lucky to [blow up] a tank, but a mission kill hit smashing up a tread or taking out an engine seems quite plausible.

[smurf]

Armour vs, IIRC, subsonic projectiles get at least twice the DR (not sure if it is 10x armour).

Not forgetting that gun laying a 12lber is going to take ages, and there is a maximum firing 13/14 skill. Therefore, after deducting distance, speed and adding size the net result is going to be miserable.

[Anthony]

22mm of WWII armor steel should be around DR 60 (penetration is normalized for RHA being DR 70/inch, and I would expect early tanks to be comparable to RHA).

Not sure about the penetration of the 12 lb gun, though. You can essentially view it as a 144 weight (5.24*scale) 12 gauge shotgun (12 gauge means a spherical lead ball would be 1/12 lb, 12 lb means a spherical lead ball would be 12 lb), and 12 gauge slugs are generally stopped by level IIIa armor (DR 12), so I'd be tempted to assign a (0.5) armor divisor.

[Ulzgoroth]

Originally Posted by The Colonel

Bit of a sanity check - is it reasonable for a low grade, early WW2 tank (say, a Japanese I-Go) to be successfully killed by a Napoleonic style cannon, possibly scared up by some Chinese soldiers?

Hi-tech gives the Bourges Mle 1853 12lber (presumably a pretty typical Napoleonic style field gun) a damage of 6dx5 (mean 105) and the FT-17 45/20 dr (and given that the FT-17 has, according to Wikipedia 8-22mm of armour against the I-Go's 6-17mm that should be representative) … which makes it look doable, but is it sane?

I'd believe it. It's really thin armor on those pieces of junk. A heavy machine gun or antitank rifle would have no problem going through them. I'd believe a black-powder cannon could do the job.

That said it would be a really impressive shot. Napoleonic-style cannons aren't very well suited to tracking a moving target. And are going to be trickier to conceal that a modern AT gun too. You probably need to lure the tank into a really narrow ambush spot so that you can aim the gun long before it arrives and just touch it off at the right time.

[PTTG]

That's what I was thinking. Considering the disparity, you might be able to get away with tricking them into overconfidence.

If you're going to ambush them, it might be a better use of your black powder to make mines and hide them under the roadway, so you're sure to get a track hit. But then, maybe you don't have the time to do that, but you do have the cannon.

[Fred Brackin]

The I-go might even have riveted armor. Put a 12-lb cast iron (not lead) cannonball in the middle of one of the frontal plates and said plate will probably radically deform and the rivets would pop loose explosively. A serious danger to the crew.

You might or might not get a neat circular hole in the armor but that armor was not but to handle that cannonball.

[RyanW]

Originally Posted by Ulzgoroth

That said it would be a really impressive shot. Napoleonic-style cannons aren't very well suited to tracking a moving target. And are going to be trickier to conceal that a modern AT gun too. You probably need to lure the tank into a really narrow ambush spot so that you can aim the gun long before it arrives and just touch it off at the right time.

At which point you've effectively made a standoff mine.

The Renault FT was pretty much only intended to be proof against rifle and machine gun fire. A direct hit from artillery was considered unlikely, and impossible to protect against while keeping the desired performance. Of course, once tanks hit the field, someone starts working on heavier rifles and more responsive direct fire artillery.

[Ulzgoroth]

Originally Posted by RyanW

At which point you've effectively made a standoff mine.

The Renault FT was pretty much only intended to be proof against rifle and machine gun fire. A direct hit from artillery was considered unlikely, and impossible to protect against while keeping the desired performance. Of course, once tanks hit the field, someone starts working on heavier rifles and more responsive direct fire artillery.

Including, of course, artillery mounted on other tanks. Which was present from the earliest operational types.

[Polydamas]

Originally Posted by The Colonel

Bit of a sanity check - is it reasonable for a low grade, early WW2 tank (say, a Japanese I-Go) to be successfully killed by a Napoleonic style cannon, possibly scared up by some Chinese soldiers?

Hi-tech gives the Bourges Mle 1853 12lber (presumably a pretty typical Napoleonic style field gun) a damage of 6dx5 (mean 105) and the FT-17 45/20 dr (and given that the FT-17 has, according to Wikipedia 8-22mm of armour against the I-Go's 6-17mm that should be representative) … which makes it look doable, but is it sane?

Those early tanks were designed to stop AP rifle rounds weighing on the order of 10 grams at on the order of 800 m/s, and you are hitting it with a ~12 pound cast-iron projectile at say 450 m/s (one source for the US Model 1857 Napoleon. If it doesn't penetrate I would expect it to cave in what it hit or shear bolts.

Edit: sectional density: 5400 grams to 10 grams is 540:1, 120 mm calibre to 8 mm calibre is 15:1, 540 / (15 * 15) = 2.4, so the cannonball has twice the sectional density of the bullet. The physics of a 120 mm projectile hitting a 20 mm plate are different than the physics of a 8 mm projectile hitting a 20 mm plate, and the physics of a soft lead bullet and a cast-iron one are different, but the tankette is not going to like that at all.