ZapTerra

The ammunition will just go back to the loaded position if your reset the large gemstone. As long as you can stop it from cracking, you only need one "bullet . I hadn't considered Stormlight consumption. Small gems would run out pretty fast.

After looking into it, rubies are pretty brittle. They might be able to be protected by a casing of some sort. The not having to reload would be pretty awesome, but just launching projectiles would probably be the best solution.

That would work pretty well, but if the gem itself could be used as ammo without cracking, then there would be no need to keep the weapon loaded with ammunition to use it. I should also add that rubies are very hard, and have a compressive strength of ~2100 Megapascals.

Maybe something to improve it could also be done with the gemstone movement isolation discovered in Dawnshard?

Yes, I was talking about the gemstone being used as ammo. It breaking would be a problem, but the upside would be that simply resetting the large gemstone would have the fabrial fully reloaded. Maybe having the small gem encased inside of a metal "bullet" would solve the issue.

Variation of distance can be achieved by conjoining differently sized gems. If an incredibly large gemstone was paired to a very small gemstone, the large gemstone could be moved back and forth over a small distance very quickly to make the smaller gemstone move out and return at high speeds. This could be used to make guns that don't have to reload, and run on stormlight. By making a device to automatically shake the large gemstone back and forth, a fabrial machine gun could theoretically be made. Are there any issues with this concept? Is it feasible that Rosharans could come to use technology like this?