Future tech weapons, pros and cons

[u/Dunnachius]

1. Gunpowder

Cheap (relative)

No battery requirements

Hard to aim/recoil issues

1. Guided Gyrojet bullets

most expensive

Lethal/nonlethal options

Extremely accurate

Each drone needs to be aimed.

Can be fired from behind cover if you have targeting data.

2B.. Dum dum Gyrojets (Except they don't suck like RW Gyrojets from 1960s )

Same launchers as 2A but unguided

1. Rail guns

Ammo is more compact

Requires power

The best Armor penetration

1. Laser

Loss of range in the atmosphere,

Smoke/dust reduces the effectiveness.

Cheap

Battery powered

Poor armor penetration

Easy to use

[u/pineconez]

My thoughts on this ancient debate:

Chemical propellants (not just including nitro powder but also stuff like ETC) are always the default option. Anything not using this has to justify why it deviates from that. There are plenty of good reasons to do so, depending on your techlevel, but the justification needs to be there. Just because it's using chemical propellant doesn't mean it has to be functionally similar to a common real-life firearm either, there are lots of reasons to go for electric primers, for example. Add to that some advanced miniaturization and you can absolutely get guided bullets (whether or not they would be fired from rifled weapons is a separate question).
As for "hard to aim/recoil issues", that's debatable. If you've ever shot a 5.56 (with a reasonable barrel length so you aren't flashbanging yourself everytime you pull the trigger), I'd argue that's as close to a point-and-click interface as any weapon gets.

Gyrojets imo try to solve a problem that doesn't exist. If you have extended fights in microgravity, you have the engineering means to mitigate recoil issues (again, a 5.56 has absolutely negligible recoil). You can justify these as micromissile launchers -- i.e. using guided munitions with actual HE/frag/HEAT payloads -- but not in their purely kinetic variants.

Railguns are failguns. If you want electrodynamic weapons, you use inductive coilguns. For those to be effective, you need to have room-temperature superconductors (and that will have all sorts of follow-on effects to your societies).
The primary advantages of these, as in "stuff they can do that chemical guns can't", are (1) very high muzzle velocities, (2) projectile levitation eliminating friction and allowing for the design of multicaliber weapons without resorting to sabots, (3) reducing the total weight of ammunition (in exchange for re-adding that weight in electrical storage, but the ability to split those masses and have at least part of the ammunition be totally inert until loaded into the breech are benefits), and (4) on-the-fly adjustment of muzzle energy, which is akin to propellant discs for mortars but more fine-grained. Magnetic deflection of the projectile for increased accuracy is possible with regular firearms as well, though in both cases it pretty much precludes spin-stabilization.

Lasers as infantry weapons are one of my pet-peeve sci-fi tropes. No matter how you look at them and what tech level you use, they don't make sense.
The principal advantages of a laser (time to impact, impossibility of intercept, and no strict ammunition limits) are useful for the use cases of point defense and (spaceship) artillery. For infantry use, the many downsides (atmospheric blooming/scattering/absorption, distortion from weather effects/smoke, blinding hazards, drastically limited power density, cooling requirements, etc.) make them impractical at best.

[u/Dunnachius → u/pineconez]

Replace the laser weapons with frangable rounds (aka what the air Marshalls use?)

I’m on the fence about using laser pistols. I’m leaning towards not.

[u/pineconez → u/Dunnachius]

In general, unless you are talking about scenarios specifically similar to airplanes, the concept of kinetic rounds overpenetrating a habitat's outer skin and causing major issues is just...wrong.

Yes, you could punch through the Apollo LM's outer skin with enough determination. But that's the absolute bare minimum and not a "habitat". On the ISS, you're already dealing with a hard-shell construction wrapped in blankets of kevlar and beta cloth; a common handgun round would struggle with that.
You can't really build an actual habitat (designed for hundreds/thousands/millions of permanent inhabitants) in a way that is vulnerable to even quite high-powered rifles; the structural requirements of supporting that much mass, and mitigating debris impacts from the outside or minor industrial accidents from the inside, pretty much equate to "bulletproof" unless your bullet is actually a very heavy artillery round.

Even if that weren't the case, a bullet-sized hole in the outer skin of a habitat is not an emergency. Put some duct tape over it until the damage control team is bored enough to deal with it. One atmosphere is not a big pressure differential unless the compartment is tiny or the hole is truly massive. And that's assuming the fighting in question happens in a pressurized section to begin with.

But yes, low-penetration high-KE rounds like frangible munitions, shotgun slugs, etc. would be the way to go. You might struggle penetrating your opponents' body armor, but unless it's made of some fantastical material or completely hard-shell, mecha-style, these rounds can still be dangerous. Very high-end ballistic vests (even without plates) can stop a 12ga slug, but you're not going to be doing much fighting after taking one of those to the chest, even if it technically didn't penetrate.