Crossbow Autococker

[malloyd]

Originally Posted by mlangsdorf

Glass marbles have a specific density around 2.7, a little less than most rock types but not terribly worse. Given that the Girandoni air rifle I mentioned upthread fired a .50 caliber lead ball at about 500 fps to achieve lethal injury at 100 yards or so, you could probably use a .50 by 2" glass slug and get similar performance. Glass isn't cheap to cast, but its probably cheaper than grinding hard stone.

And if you really like crossbow bolts, nothing prevents you from designing a weapon that launches sharpened wooden bolts with a gunpowder charge rather than a spring. Nobody does now because bullets are lighter, and probably better, but it shouldn't be hard to design something that will outperform a crossbow spring.

Of course serious weapon designers might go with metal bullets anyway. If fancy machinery is even vaguely affordable, the cost of metal bullets can't be *that* high, at least for single shot fire. The pound or two of metal I'd need for an air tank and complex cocking mechanism could make a couple dozen bullets too, and I'm not likely to kill more than a dozen people with a crossbow either. We're talking about life and death here - people pay a premium for stuff their lives depend on.

[malloyd]

Originally Posted by Derrick_rp

Glass! I would have never thought of that, but that’s a great solution. Do you think you’d be able to use it in a conventional firearm, or would the glass shatter in the barrel?

Should be fine for black powder smoothbores anyway. Glass is actually a pretty tough material, and it's not like you care all that much if it gets a bit chipped or cracked, as long as whatever's left of it still flied straight.

You might want to look for the youtube videos of the guys who test fire weird stuff - some of them have gotten OK results out of glass shotgun slugs, and that's with basically no serious R&D time.

[mlangsdorf]

Originally Posted by Derrick_rp

Glass! I would have never thought of that, but that’s a great solution. Do you think you’d be able to use it in a conventional firearm, or would the glass shatter in the barrel?

I'm less confident than Malloyd about glass, but a thick slug in a low pressure, low velocity gun should be fine. You can approach the speed of sound with black powder, and that might not work so well. But at 500 to 750 fps out of a long barrel with a long slug, glass is probably strong enough.

It's going to have bad armor penetration against metal, but it sounds like metal armor would be rare. Against flesh, it's 2 ounces of glass hitting at 400+ fps: crippling if not fatal.

[Varyon]

Originally Posted by malloyd

Of course serious weapon designers might go with metal bullets anyway. If fancy machinery is even vaguely affordable, the cost of metal bullets can't be *that* high, at least for single shot fire. The pound or two of metal I'd need for an air tank and complex cocking mechanism could make a couple dozen bullets too, and I'm not likely to kill more than a dozen people with a crossbow either. We're talking about life and death here - people pay a premium for stuff their lives depend on.

There's also the fact that you aren't simply throwing the metal away. During practice (which is when most ammunition is going to be used), you just need to make certain you have a proper backstop to catch all the bullets, then just scavenge and recast later. It would likely become common practice - if a bit morbid - to dig bullets out of corpses after a battle as well. The misses will mostly be lost, although you may have some poor folk eke out a living by searching old battlefields for metal bullets to sell to the military.

Originally Posted by malloyd

You might want to look for the youtube videos of the guys who test fire weird stuff - some of them have gotten OK results out of glass shotgun slugs, and that's with basically no serious R&D time.

Indeed. Note those slugs were made with bits of metal inside that screwed up their balance as well as probably weakened the glass, yet one of the rounds stayed completely intact and another only experienced a single break (splitting in half), and even the two that shattered still maintained a large enough chunk to do some decent damage. Made without those bits of metal and properly balanced, I'd imagine those would do pretty well, and that's up against modern powder. They should probably still count as Frangible (HT 167), however.

[mlangsdorf]

One solution to the frangible glass slug problem would be a metal nose and jacket. Basically a metal cup filled with glass. Even if the glass shatters, it should stay inside the jacket and deliver energy and momentum to the target.

A metal jacket would also allow the gun to be rifled, further increasing accuracy. You might be able to rifle the gun with pure glass slugs, but it should definitely work with a metal jacket.

At TL 6 or late TL 5, a manual action, rifled, air powered repeater discharging metal jacketed glass slugs would e very possible and an adequate weapon for killing humans.

[Anaraxes]

Rather than carve individual stone bullets, you could cast concrete into bullet shapes.

Densities for high-density concrete can go to a bit more than half as much as lead (over 6000 kg/m^3), almost as much as iron. But the highest numbers probably don't apply to the setting, since they start to use minerals for the aggregate like hematite or magnetite -- and if you've got a lot of iron ore lying around to use in concrete, iron isn't going to be all that scarce, unless somehow the setting never figured out how to smelt it. Can pretty easily match or beat marble, granite, or glass, though, and it might be easier to work than glass, as you don't need the high temperatures.

Glass bullets do sound cooler, though :)

[ericthered]

While we're suggesting various materials you could replace the metal with, may I suggest brick? It may be cheaper than sone of the other options

[Derrick_rp]

Originally Posted by mlangsdorf

One solution to the frangible glass slug problem would be a metal nose and jacket. Basically a metal cup filled with glass. Even if the glass shatters, it should stay inside the jacket and deliver energy and momentum to the target.

A metal jacket would also allow the gun to be rifled, further increasing accuracy. You might be able to rifle the gun with pure glass slugs, but it should definitely work with a metal jacket.

At TL 6 or late TL 5, a manual action, rifled, air powered repeater discharging metal jacketed glass slugs would e very possible and an adequate weapon for killing humans.

Would a plastic jacket do the job? The characters have more access to plastics than metal.

[johndallman]

Originally Posted by Derrick_rp

Would a plastic jacket do the job? The characters have more access to plastics than metal.

It needs to be pretty tough and heat-resistant plastic. There's quite a bit of force and friction being applied.

[Ulzgoroth]

Originally Posted by johndallman

It needs to be pretty tough and heat-resistant plastic. There's quite a bit of force and friction being applied.

Plastics are used for some cannon driving bands. It seems like you could probably make a material that can do that hold up passably as a bullet jacket.