Loader efficiency is inconsistent between railguns, coilguns

I noticed that railgun autoloaders are far worse than the ones on coilguns and started looking for a reason. Turns out railgun loader efficiency depends on the mass of the projectile and the diameter of the entire barrel assembly, whereas with coilguns only mass and diameter of the projectile affect the efficiency. This means that for a similar projectile and barrel, a coilgun loader with identical loading time can be ten times lighter than the one on a railgun, especially since railguns tend to have very thick rails. I'm fairly sure there's a bug here in one direction or another, the current situation doesn't make a lot of sense to me.