Most of the things that I could add here have been covered. One point to emphasize about recoil is the muzzle energy is mass times velocity squared, while momentum is mass times velocity, so the 4 gram 1500 meter per second Gauss round has a lower momentum than a heavy normal velocity round of equal muzzle energy.
One point that hasn't come up is that a conventional round propels not just the bullet out the barrel, but also a lot of the propellant gases. Those gases aren't pushing on the weapon to generate recoil once they clear the barrel, but they do until then. With an energetic propellant, the mass of the bullet is quite a bit larger than the propellant gases, but there's more coming out the barrel of a conventional rifle than the bullet.
Another point not mentioned is the Advanced Combat Rifle, described as the ultimate development of rifles with chemical propellant. It has all the firing solution and helmet mounting stuff included, well before the Gauss rifle becomes available. Presumably all that would be present in the first military Gauss rifle, because it's standard equipment by then.
There's also the matter of stabilizing a round. Fitting four grams of anything into a 4 mm diameter round gives a long stick of matter. Spin stabilization requires higher spin rates for longer rounds -- really high for a Gauss round for any real world metal. But maybe at TL12, the armor piercing core could be some science fiction 40 density metal, and the jacket is normal 8 density mild steel. But even that isn't a complete solution, because putting the high density stuff in the core doesn't help the spin stabilization as much as a dense outer ring would. Maybe the puzzle of how to put so much spin on the round is part of the reason the Gauss rifle is a TL12 development.
msprange wrote: ↑
Thu Nov 09, 2017 9:26 am
Variable power gauss weapons? I like that, might have to investigate it for a future adventure or supplement
To be honest, I thought I saw that already, described as an optional version that could fire the rounds at selectable velocity, even as slow as subsonic, which makes a practically silent weapon. Real weapons with "silencers", more formally "suppressors", are still pretty darn loud, not at all like they're portrayed in most movies. But a subsonic Gauss round might be as quiet as a movie silencer.
To save looking things up, the speed of sound is about 340 meters per second. To offer a 10% safety margin, assume that the subsonic Gauss round is about 306 meters per second. That's 20.4% the regular velocity, so it has about 4% of the regular velocity round's muzzle energy -- very close to that of a .22 LR round. So by switching the Gauss rifle from full power to subsonic, you go from the ultimate development of the slug throwing weapon to the rifle I fired as a kid at summer camp. At range, a sturdy leather jacket could probably stop it.
Of course, if the weapon can be tuned down to subsonic, it can also be tuned to an in-between velocity with enough power to do its damage while reducing the recoil enough for the soldier's ability to handle the recoil. Maybe the tunable Gauss rifle has five settings, for full, 80%, 60%, 40%, and subsonic, with full, 64% 36% 16%, and 4% damage.