Upscaled infantry weapons for upscaled men

Question

I have asked a similar question before, but this time, the setting is somewhat different. Replace 'Giants' with 'Mechs' or 'Powered Armor (PA)' for instance, and fast-forwards maybe 2000 years.

Could you simply upscale a modern assault rifle and expect it to work reasonably well against a moderately armored target (think armored car rather than tank)? Or would all weapons devolve into things like RPGs and AT guns? How about things like grenades, can you upscale those?

Note about size: The Mecha/PAs are roughly 5 to 6m tall. Nothing too extravagant.

Answer 1

The short answer is, yes you can.

Modern anti-materiel rifles are basically sniper rifles with a little more power. They typically fire .50 caliber or 20mm armor-piercing rounds. Machine guns and autocannons of these calibers are commonly used as vehicle-mounted weapons. It isn't too hard to imagine these weapons being modified to be hand-held by someone or something 3 times larger than a normal person.

As you suggest in your question, these weapons are not effective against tank armor, but they can damage less heavily armored vehicles. The standard ammuntion would probably be of the kinetic energy penetrator type. These have a high-density core of a tungsten alloy or depleted uranium with a lightweight outer shell that is discarded when the round is fired. This means that the projectile moves faster than a regular bullet and transfers the impact to a smaller area, allowing them to pierce through armor.

As for grenades, I'm with DaaaahWhoosh—there's not much reason for armored mechs to use them. At least, assuming that regular infantry use powered armor, and there aren't many unarmored targets to use them against. There could be use for rocket-propelled grenades, though, as they can be used against armor. There are HEAT rounds, which use a shaped charge to propel a stream of metal at hypersonic speeds through armor. Also used are HESH rounds, which use a plastic explosive that spreads across an armored surface before detonating to send a shockwave through the armor and damage things inside without piercing the armor. If there is a use for shrapnel in your setting, HEAT rounds can be modified to become high-explosive dual purpose weapons by adding shrapnel elements to the outside of the explosive charge.

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Edit: If you really want explosive handheld grenades, your mechs are probably big enough (and your technology advanced enough) to consider low-yield nuclear weapons. The smallest device known to have been made, the W54, weighed about 50lbs and had a yield of about 10 tons of TNT. According to the Wikipedia page linked above, it could destroy an area of two city blocks, which works out to a radius of about 250 feet. So, it is very destructive but it still seems plausible that a mech could throw it far enough to be safe. Later versions had up to a 250 ton yield, which might exceed the "throwable" range, though.

Answer 2

I came across the Lahti L-39 when looking into this question; apparently it's an incredibly large sniper rifle used to shoot through tanks. It seems to have fallen out of use after WWII, but I think if you have mechs then you have the technology to bring it back, better than ever.

Also, many warfare vehicles come with a 50-cal machine gun attached somewhere. Such guns are great at taking down infantry and piercing light armor, but are too big to be carried by an infantryman. That won't be a problem for your mech.

As for grenades, I don't really see why a mech would carry an extra-large one. Grenades don't have much benefit against armored targets unless they're inserted past the armor; funnily enough, many RPGs are designed to pierce armor, then explode. You can't penetrate armor by throwing something at it (unless your mech is designed to throw things at armor-piercing velocity, at which point what's the use of guns?).

Answer 3

I suppose you could just scale up assault rifles, but why would you want to?

Belt fed mounted guns would probably be a bit more efficient, giving you higher and more sustainable rate of fire, as well as leaving the hands free. If you're just looking for larger rounds, we already do that, from .50 caliber all the way up to the howitzers' 8" and beyond.

Grenades could be unscaled pretty reasonably, but the bigger the boom the further away you want to be when it happens, so a launcher may make sense, but I suppose a large Mech could throw them by "hand".

Answer 4

I would hope that with 2000 years of development small, portable, extremely powerful energy sources would power the mechs. At that point, why would you use conventional bullets especially with their drawbacks of their weight, size and limited supply?

Instead you would surely use a energy weapon (yes, laser/maser/phaser) if possible. While it is a bit of a SF cliche, it does make sense in this context.

But if conditions (range, dusty atmosphere, water vapour) make lasers unsuitable, my preferred fallback would be a rail gun using small aerodynamic metal slugs. These would be much easier to carry than conventional ammunition, but be just as destructive, perhaps more-so. Their high velocity give them great range and lots of damage, even with a very small size of projectile. They could be fired in intense bursts to cut down targets. (I personally cherish the idea of knitting needle-like projectiles fired at hypersonic speeds cutting through anything they encounter). Or, if you prefer, you could go with larger projectiles for greater kinetic energy which would smash a large hole in the target.

If set way in the future, perhaps the projectiles could have built-in targeting and guidance, making them harder to evade and overcoming problems with accuracy at long range.