In my previous question a guy called Thorne pointed out that I could make a high-velocity coilgun without using a barrel of enormous length by taking a page out of the LHC's book and using a circular coilgun, allowing the projectile to run several times around the track. That particular question wasn't really about coilguns, though, and I had another previous question that was. In my coilgun question, the most reasonable answer suggested that a coilgun with a 100 meter-long barrel might, just might be able to get a fairly small projectile up to about 30 km/s, but almost certainly couldn't do the same with fairly massive one. So, does the answer change if I'm using a circular track to accelerate the shot? Let's assume the track I have to work with is about 300m in diameter, and once again my goal is to get a 1000kg projectile up to about 30 km/s. I suspect that the mass of the projectile will once again be a problem, though; and I suspect that the design of the accelerator will probably lend itself more to a constant stream of ball-bearing sized iron shot.
EDIT: To clarify, the idea behind the circular coilgun is that a projectile can run around the track more than once before it is fired. The barrel length of the gun is thus effectively infinite (or rather, unlimited), it can be however long it needs to be to get the projectile(s) up to speed. I just don't know whether this makes it practical or not.
And on a related note, what about use of an actual ring-shaped particle accelerator as a weapon? Devices like the LHC are kilometers in diameter, and while they can get their particles up to nearly the speed of light (from what I've heard), the actual destructive power of the beam isn't that great. I don't need a particle stream anywhere near that fast, as long as I can dump enough mass into the beam for its effect on the target to be worthwhile. Is a 300m diameter ring anywhere near enough to be useful? Can such an accelerator be built as a weapon?
Maybe that's why the Enterprise has a circular saucer section...