

Obviously if its something more powerful the RE factor would modify that.) If we figure the M118 round (11 gram bullet roughly) and call it 3-5% of mass as explosive it would be between a third and a half of a gram (about 1400-2100 J per bullet assuming TNT. A german APHE round like the link had maybe a few percent of the mass as explosive relative to the shell. You just make an estimate about the percentage of filler that might be in the round. I honestly think its just another of those Halo Firearms things where 'kewl' and 'wow' factor drive the design more than awareness of how those things actually work Again, what would be the point apart from making the thing needlessly complicated.) There has been talk of plasma 'shields' being used as a means to allow planes to achieve effective hypersonic flight I believe, but that might not scale down at all (And I doubt you want to argue that it has magic plasma generators in it just to achieve that. The real concern I would wonder is 'why is the round HE at all?' because at those velocities (hydrodynamic to hypervelocity) there's very little chance of the projectile staying intact anyhow - it will probably explode (or the next-best thing) simply from the impact itself. Not exactly an ideal stealth/assasination weapon!)

so there should be a huge glowy and noticable plasma field around that.

Actually now that I think about it that's the same problem with the Stanchion (at 15 km/s, it would be in the same 'atmospheric reetnry' threshold, and atmosphere at ground level is MUCH denser. hard to say) and it would create recoil issues with the ARC-920. Even assuming you didn't melt the projectile, the side effects on bystanders of such probably would not be good (blindness, flash burns. thing is it usually only hpapens during things like atmospheric reentry and similar. Well you can kinda get a plasma around a fast moving projectile.
