# Sci fi setting: Are smaller and faster bullets automatically better?

I’m building a world where two civilizations are meeting, and both have fairly different design philosophies with weapons and armor, and the easiest way to sum it up is think Mass Effect without the relay network needed to travel, so they have weapons that fire tiny bullets really fast but also have to deal with overheating, and they also rely more on kinetic shields and barriers with very minimal armor, and they’re fighting a civilization that instead went bigger, building their troops up with large amounts of armor, exo-skeletons, and large caliber weapons that are also magnetically propelled but not as fast as their enemy’s weapons. Their ship designs also represent this. I want to know if the smaller and faster weapons are automatically better than the larger caliber ones because I don’t want it to be a total stomp for one side

Edit: Meant to clarify that I’m talking about on the ground, infantry warfare. As for the side that specializes in armor, we’re talking incredibly thick, heavy, and incredibly dense alloys used in this armor that it necessitates exosuits just to move faster than a stroll. As for how the kinetic barriers work, I’m still figuring that out as that is part of the reason I was worried that this would be a total stomp for one side if I just said “they block anything and everything and it takes sustained fire to take them out, no matter the projectile size”

• Are these smaller faster weapons on a planet or are they fighting in space? Dec 13, 2022 at 22:48
• What material are they, and can you give more description of the weapons? Dec 13, 2022 at 23:30
• Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Dec 13, 2022 at 23:30
• Infantry-against-infantry battles went out of fashion in the 1950s. The man-portable weapons carried by soldiers are most for show, and for use in what are essentially police actions against goat-herder barbarians. Right now there is an on-going war between Russia and Ukraine, two semi-modernized powers; have you heard of many infantry-against-infantry battles in Donetsk? Or is the war carried out mostly with guided missiles, unmanned aerial vehicles, and artillery? Dec 13, 2022 at 23:45

From what I understand, you're mostly worried that one power might crush the other. However, remember that outside historically-accurate stories, you are in control of your balance, rarely your world. If you want big guns making ludicrous bloodbaths, you can. If you want a tiny gun destroying buildings, you can too!

Even with real-world weapons, you'll see that scriptwriters often adapt their overall potency depending on what they wish to convey... When they're not meddling with ammo clips for specific scenes. On their side, game designers balance their game a lot of the time, too. Yes, through (lots of) trials and errors, but it's only because people will put the tactics to the test, rarely because they think the weapon is ridiculous from a world standpoint. Point is, few people will complain as long as you don't dive in the extremes (e.g. : punches exploding tanks). This works for most worlds, including deep, space-opera worlds like Mass Effect's.

To effectively balance each tactical asset, you need to think them one relatively to another and under conditions rather as absolutes (read whether they're "automatically better" than other). Also, wonder "why" do this empire like this weapon or another. Why this weapon is better than this one on open-fields and against mechas? Do they like this weapon because it's ultra-cheap? Or is it because it is (or was) strong against a recurrent enemy, or because it works best in some specific land type they live? As you get more and more of these questions answered you should more easily explain why this war is balanced or why one side struggles. In other words, it will make your world feel more balanced.

Very important note : be consistent throughout the answers you give to the above questions : If round X pierces a tank's armor and similar round Y is even more powerful than X, then Y is likely to pierce it, too!

## Now to the stated question : each ammo its usage

There's no "always stronger" weapons in real-worlds and most fictional ones, they are adapted for some situations and not others. As such, bigger ammo isn't always better, nor smaller is. Still, people will associate traits with some ammo kinds. Here are some attributes (physically and artistically) commonly bound with small ammunition :

• You can carry more ammo, both in clip and on yourself. That's actually how they explain infinite ammunition capacity in Mass Effect 1's gameplay.
• Weapons are lighter, smaller, easier to handle and even concealable sometimes. You also have less recoil.
• They have faster firing rate and lower reload time. Great for saturating areas like with machine guns.
• But they have lower destructive power : They don't pierce armor very well (even though it can saturate shields) and explode rarely (they don't have/have less explosive payloads).

As for heavy ammunition, it's just the reverse. They have higher destructive power which can lead to area of effects (i.e. explosions). However you can carry less ammo, weapons are bulkier, their firing rate is lower and reload time higher.

Finally, as told by others, shot speed plays a major factor in feeling a weapon's destructive power. For the same mass faster is generally stronger. It's actually one lever designers often pull to make smaller ammo feel more destructive.

Recall, the above is not to be used as a strict and impervious reference, it's just what people will tend to think at first! For instance, slow firing, armor piercing yet with tiny-ammo railguns have already been made convincingly! The few limits you can't really dodge is ammo capacity and that your weapon cannot be -obviously- smaller than your ammunition :).

I actually had similar question here: How to best miniaturize firearms? The idea is to go mechanic route as far as possible, assuming massive energy shortage

Yours is a little different, so keeping above in mind, let's do a quick comparison of smaller projectile versus bigger:

1. More rounds per loadout (i.e. going from NATO 7.62 to NATO 5.56 gives you 40% more rounds)
2. Less weight (same loadout of 5.56 NATO is less than half the weight of 7.62)
3. Less recoil
4. Less range - 5.56 is good up to 500-600m, 7.62 can go nearly twice as far and still transfer significant (and compared to 5.56 at 550m) energy to the target,
5. Less energy transferred to target
6. Less flat trajectory (Though not that much - about 5% less than 7.62)
7. Less accurate (meaning lighter projectile is more susceptible to weather/atmospheric conditions)

It's worth mentioning that it's not like after 600m 5.56 suddenly stops - it just starts tumbling unpredictably, which may cause it to miss the target. Projectiles have high maximum range (for example minie ball is lethal at over one mile even), it's the effective range that counts - range at which there is a reasonable expectation of hitting a target.

The lower you go on size and mass, the more pronounced the difference will be. So the real question here is: what is the method of propelling the projectile? I mean - smaller it is, the more kinetic energy to impart is needed for it to compete with bigger round. As mentioned here, in the thread: lethality is a function of mass and velocity...

In my opinion - and I'll refer you again to link at the start - the only possible way for going smaller is to either have completely different method of energy transfer, giving much higher speed without significantly increasing the amount of the propellant, or build a drive that would accelerate projectile all the way to the target.

Currently it's mostly controlled explosion and driving the combustion gasses in one way, propelling the projectile through the barrel (and the longer barrel for same explosion imparts more energy) or railgun/coilgun (experimental still; I know it's not the same, but not in principle)...

So if you have the tech to build a tiny engine, one that would accelerate your projectile AFTER it left the barrel, you're golden. Concept and even technology is there already - SCRAMjet projectile, if accelerated to high enough speed initially - but building such rounds for a firearm is not as easy as it sounds (and may not be possible to miniaturize below certain level). Concept is solid, though, there have been vessels built using it. Then projectile can go to and maintain middle to high hypersonic speeds. Scramjet bullets in theory could move so fast, that with the compression of the air due to their design, they would use just the atmospheric oxygen as fuel, again in theory making them both long-range and high-damage.

5.56 has about 1kps muzzle velocity which is Mach 2.9, which technically is still supersonic (that is: less than Mach 3). So high hypersonic is 7-8 kps (Mach 20 to 23), and if you can go ultrasonic (I know, it's not exactly how the word is used), you could have really small projectiles with one heck of a punch.

So question is: what is your tech base? If not enough, then I refer you (again) to the linked question.

• worth mentioning above a certain speed energy transfer actually starts to go down because the projectile just goes through the target. which does a lot less damage to the target.
– John
Dec 14, 2022 at 12:37
• Note that there is a name for a projectile which carries its own means of propulsion after being fired. At that point, it's just called a missile. (Or possibly a torpedo if it's in water. Star Trek calls them torpedoes even in space, and some others have followed suit, but it's the same general principle.) You could also call it a rocket, though this tends to imply something much larger. Though "rocket propelled grenades" (RPGs) can be smaller. Dec 14, 2022 at 21:07
• @John - which is exactly the problem with 5.56 NATO at low to mid ranges ;-) However, this may also not be a problem, because over certain speeds energy transfer is just part of it, there are also secondary effects. So if pebble of sand goes ultrasonic through or near target it may go through with little damage, all right, but the sheer speed means there will be also a shockwave, and unarmored targets can be soft-killed with that - this is called hydrostatic shock, and it can be a thing just from near-miss, and urban legend goes that with .50 BMG it is not uncommon. Dec 15, 2022 at 8:44
• @DarrelHoffman Yeah, I agree. There is no good solution in naming conventions nowadays, so it's sometimes better to leave a misnomer because proper name will just confuse. Dec 15, 2022 at 8:46
• "Energy is mass multiplied by speed", that would be impulse, energy is E=0.5 * m * v^2. Dec 15, 2022 at 10:59

Mass x Velocity = Force

Smaller is better only really applies when it comes to carrying and storing ammo.

The whole point of guns is to put holes in things that shouldn't have holes in them and the bigger the hole the better.

Now the real advantage of small is if you're firing 2mm ball bearings is a magazine might hold 1000 rounds while a 50 cal sized mag might hold 10 rounds.

Now you have a couple of options to compensate for the small rounds. You can simply fire more rounds faster. If you're firing tiny rounds at 100 per second, you can effectively cut something in half.

The other option is expanding. When something like a hollow point round hit something, it expands out and breaks up so it's a small hole where it hits and a massive hole where it exits

The advantage of big rounds is they always make big holes. More mass always means more force. A bullet can go through a body and the person could keep fighting but a cannonball is always going to wreck their day.

Another advantage is you can pack extra goodies into a large round. Depleted uranium rounds? Tungsten core armour piercing rounds? laser guided smart rounds? Explosive rounds? Incendiary rounds? Frag rounds? Smoke rounds? Neurotoxin rounds? Gas rounds?

Larger rounds are more powerful and more flexible.

Dragon's breath Shotgun shells

Frag shotgun shells

Beanbag rounds

• Bigger is not always better ^^. Two things to explain : If you pierce your target and hit friendlies/civilians behind, it's not really neat. Then, if you're really devious, you might want the enemy to stock up and maintain wounded soldiers than digging graves for dead ones. The Geneva conventions won't like the last one, though :p. Dec 14, 2022 at 0:54
• RE:DU and other AP rounds $Force ÷ Area = Pressure$ is the guiding principle. DU is good because it allows to craft a projectile with a small cross-section and contact patch, while being strong enough to not completely vaporise on impact. You could conceivably achieve a similar result with a tiny ball of the right material. The real issue here is that while a tiny ball could penetrate easier, that's not always desirable, and woefully inadequate when you need stopping power. Dec 14, 2022 at 9:52
• @Tortliena : smaller and faster bullets increase this problem, they don't decrease it. The question is about using the same energy to propel a bigger round versus a smaller but much faster one. A smaller and faster round (like a flechette) is more likely to overpenetrate, which both means it can hit something beyond your target (or behind walls if you miss) and that less energy is soaked up by the target, therefore doing less damage.
– vsz
Dec 14, 2022 at 11:26
• mass x velocity = force -> I don't think so. The energy of a projectile is proportional to mass times velocity squared, and energy is what delivers the punch. Force is equal to mass times acceleration, and comes into account when the projectile hits the target. If it is stopped very fast, it will impart a very large force (large accel.), while if it is stopped slowly, it will impart a slower - albeit longer duration - force. Dec 14, 2022 at 12:59
• mass x velocity = force <-- that doesn't make much sense, unless you have some very unusual definition of "force". A more correct formula would be mass x (velocity squared) = energy. But note that the amount of energy you give your bullet is probably fixed by your gun; the formula mass x velocity squared = energy can be rewritten velocity = squareroot(energy / mass), which means that if you fire a heavier bullet but give it the same energy, then it's going to be slower.
– Stef
Dec 14, 2022 at 13:20

No, small bullets are not automatically better.

1 - Bullets loose speed based on the atmospheric density, and the faster they are the faster they slow down. Their is a practical upper limit for the maximum speed before its all just wasted in friction.If we were fighting underwater then a "bullet" the size of a container ship could kill me even fired from miles away,going only very slowly (we assume I do not swim out the the way). In contrast a small bullet, no matter how ridiculously accelerated it is, will not make it far through the water. This gives a nice way of explaining how your civs went different ways (if you want too). Perhaps one hails from a planet with double or more the atmospheric density of the other.

2 - Assuming you can fire rounds at a speed, such that more speed would largely go to waste in atmospheric friction, then larger rounds let you pack more punch.

3 - Whipple shields (https://en.wikipedia.org/wiki/Whipple_shield) can be used to stop extremely fast and small projectiles. These are very thin (maybe think of tin foil) layers placed several meters in front of your main armour. If a tiny bullet at incredible speed hits the tinfoil it cuts right through it like butter without even slowing down, but that tiny friction it gets from cutting through that tinfoil can heat it up so much that it melts or evaporates into a gas. Then the main armour behind just gets hit by a really fast burp, rather than a really fast bullet.

4 - A bullet that is too small could sail right through a target while inflicting very little damage on the way through. Imagine a tiny little cut line right through the target, maybe it got hit by a relativistic dust grain. That might not be so bad.

I upvoted @Thorne's answer and you should to, but I'd like to put a different spin on it.

To every thing there is a season, and a time to every purpose under the heaven.

The equation F=mA is absolutely true. Kinda. The idea that two objects, varying in mass and acceleration such that each impacts the target with the same force, would result in the same amount of damage isn't completely true.

I offer, for your consideration, the idea of a BB-sized plastic sphere vs. a 1kg tungsten sphere. Acceleration is adjusted such that both impact a steel shell with a reasonably considerable and equal force. What would we expect to happen?

The plastic BB will vaporize in a fantastic ball of glorious heat. But otherwise do a whole lot of nothing.

The tungsten sphere might just bounce off, but only after leaving a decent dent — if not actually piercing the shell.

That plastic BB at the acceleration just considered would be a whomping good anti-personel weapon, but a nearly useless anti-tank weapon. Sending out 10,000 plastic BBs that add up to the force of a single anti-tank weapon simply won't do the job. In like manner, the tungsten sphere would be a good anti-tank weapon, but a lousy anti-personell weapon (unless all the soldiers are conveniently standing in a row).

There's a reason any good military on Earth has bullets and/or shells of all shapes and sizes, of all makes and types. There's no such thing as one bullet (or one weapon, for that matter) that's the right bullet for every job.

Then there's wind...

Then there's the problem plaguing all small things: wind (and water, and other forces...). The problem with F=mA is that it also works in reverse. The force needed to, for example, deflect a small mass is less than for a larger mass. It doesn't matter if we shoot one plastic BB at an incredibly high acceleration or 10,000 at, well... 1/10,000th of that one BB's acceleration. They're all equally suseptible to the same wind force. Wind... water... magnetism... heavy is your friend if you want your aim to be true.

Except for gravity. That's perhaps the one force that benefits light over heavy.

TL;DR

Sometimes smaller is better. Sometimes bigger is better. The assumption that one could always outshine the other is too simplistic. If your worldbuilding is for the purpose of a game, then all this doesn't matter because the presentation of combat is only an aesthetic. All this only matters if you have a reason to reflect Real World physics in your worldbuilding.

• It will be a total stomp for one side. The side that can put two and a half ounces of lead into somebody on the other side of one inches of steel plate at 200 yards at 1000 rounds/min or less, because anything more than that is just for keeping heads down, and why the M2 is basically just an intentionally slowed down MG-42 with a higher caliber and is one of the most ubiquitous weapons on the planet. Dec 14, 2022 at 7:13
• That is just plain wrong. Mass doesn't matter. It's energy that is important. If that BB round of yours has greater kinetic energy than your big metal slug it WILL deal more damage to the armor. And if you accelerate your projectiles to a high enough speed (which OP implied by referencing Mass Effect technology) there are relativistics efects in play. So that BB round can be heavier than 1kg of metal... Dec 14, 2022 at 8:07
• @Negdo caveat: armor penetration also requires higher sectional density in the projectile then in the armor plate. Otherwise the kinetic energy will just ablate the upper layers without getting through. "Newton's approximation for the impact depth" is a good rule of thumb for those kind of interaction. Dec 14, 2022 at 11:03
• @RobertMartinu If you get hit by a high enough energy projectile it will penetrate. Armor has a limit in his maximum impulse, so if you have high enough momentum, a hit will do it's job. Projectile will most likely be in plasma state anyway on hit, so talking about density of a bullet is kinda pointless. Dec 14, 2022 at 11:37
• @Negdo It's simply not that simple. What the mas is composed of is not considered by the force calculation, but it's relevant to the elastic collision between the two masses. In other words, we're not considering all of the necessary equations. I just didn't bring the rest of them into play because I'd have to dig through some old physics texts to find them. Think of it this way: you can throw a minnie ball and a modern stell jacketed bullet - each at the same mass and with the same acceleration - and the results will be dramatically different. Even the shape of the bullet matters.
– JBH
Dec 14, 2022 at 16:53

It is likely that your rounds are limited by kinetic energy that magnets have managed to put in the bullets. So, having a bullet fly twice as fast means it needs to weigh 1/4 of the original one. This means the bullet packs half the momentum. Half the momentum is both good and bad. You will feel less recoil... but your target will feel less recoil too. Assuming bullet stops in your exoskeleton body, being shot by a 100g chunk travelling at 100 m/s will make you stagger. 1g chunk travelling at 1 km/s (note - 10x higher speed => 100x lower mass) will only make you flinch. In this scenario, heavier weapons are generally better in terms of smashing opponents, but because of recoil they are going to be less accurate. Side with heavier guns also packs much heavier armor = they weigh more. This opens up possibility of having higher kinetic energy for larger guns, making momentum considerations even more lopsided. Additionally, smaller bullets take up less space; but I believe the main limitation would be battery packs (or whatever energy source) for those guns.

IF your bullets are limited by momentum (your magnets are powerful enough so the only limitation is to not fly after firing), having smaller caliber guns means they will pack way more kinetic energy. Perhaps not that much more if side with heavier weapons has more weight. Counter-intuitively, soldiers with smaller caliber guns will run out of ammo faster - they will deplete their battery packs faster. Even faster if heavier soldiers carry more battery.

On the other hand, you have impact depth - density ratio * projectile length. It is unlikely that armor has higher density than the bullet, so as long as the bullet is long-ish, it WILL penetrate the heavy armor. This poses problems for the heavily armored side ((I don't know about your energy shields, so you can handwave that bit if needed))

Making some assumptions and confining the answer to space warfare (and hence vacuum). Assuming that some form of convention propulsion like a fusion drive is needed by vessels for 'in system' travel in addition to the FTL drive that lets them travel between the stars up to a point 'smaller is better'. This is because the velocities used in space travel are high enough (in virtually all circumstances) to impart significant Kinetic energy (KE) to any object fired from one ship at another. Without specific examples of difference masses its hard to calculate but the formula is as follows:

KE = 1/2 mass (of the projectile) x velocity squared.

So you can see that as velocity increases the amount of energy released on impact rises significantly. Depending on the size of the vessels and their speed at some point even small projectiles traveling at very high velocities (relative to the target) are going to inflict significant damage on any vessel hit.

If rail guns for instance are the primary space weapon having smaller (less massive) projectiles means not only can the rails guns be smaller but the power requirements are also reduced since smaller projectiles require less energy to reach your required velocity than larger (more massive) ones do. On top of this not only can you carry more ammunition but potentially you can add additional guns to up your rate of fire. Finally lots of smaller projectiles are harder for an enemy to detect and intercept and/or evade than a few large ones.

So in space at least provided you can launch your projectiles at a velocity that is sufficient to puncture a known quality of enemy armor smaller IS better.

• if they consume less energy in firing they also deliver less energy to the target.
– John
Dec 14, 2022 at 12:40
• @John As I noted re; the equation for kinetic energy impact energy is (mostly) defined by relative velocity. In the case of space battles the relative velocities of the 2 ships involved matters as much if not more than the velocity a projectile reaches after being fired by one ship or the other. Lets assume 2 ships are closing on one another at say 100,000kph (about 28kps). That velocity gets added to the round in ADDITION to its own intrinsic velocity. So if the a round is launched at a muzzle velocity of 10 KPS & hits the impact velocity is 38kps not 10.
– Mon
Dec 14, 2022 at 22:28

There is no always better.

A lot of the benefits in land warfare (light means more rounds) are discussed elsewhere, so I'll address effectiveness and role.

I think the more important question is what are the weapons built to accomplish.

A light projectile has less mass so you can accelerate it fast and you can also decelerate it fast, so your effective range is likely pretty small even if your maximum range is very long.

You'll have three modes with a fast, light projectile: overpenetration: hit the target with a needle going Mach 3 - punches through and deposits basically no energy underpenetration: hit the target with a needle thrown by a 12 year old - no energy left after flight drag effective: hits the target with enough kinetic energy to be lethal - due to low mass, crumbles and collapses on impact, imparting all energy to the target

If these are battle rifle-type weapons, I'd presume they're designed to be effective against those who use them. In that case, I'd presume their users are insect-like. Very fast, stealthy when they want to be, can change direction quickly and have little to no muscle, but potentially carapace. In this case their doctrine would likely be to spread out and ambush using a triangulation of crossfire to fill the target area with rapid, effective fires at medium to close range and aiming for soft parts (head, eyes) with point fire. If the enemy closes the natural overpenetration of the weapons makes them more likely to pierce carapace, so lay down heavy grazing fires at center of mass targets. Their engagements would likely be mostly silence followed by a massive, violent scrum. They'd focus a lot on movement, tracking and situational awareness. Maneuver and unit cohesion would be key as well as furious and uncompromising personal combat. There likely wouldn't be snipers or designated marksmen. Being alone makes you prey. Even if you knock down one, there are fifteen behind you.

On the other hand a heavy projectile has lots of mass, so even though you can't accelerate it fast you also can't decelerate it fast, so your effective range is likely quite long even if your maximum range is shorter.

You'll have the same three modes with a slower, heavy projectile of over- and underpenetration, as well as an effective range, however your effective band will take up more of the maximum range. Overpenetration is also likely to be lethal. Shooting a needle through a target is not fun, but likely not lethal. Driving a softball through a target is likely going to be lethal, even if most of the energy stays with the projectile.

If these are battle rifle-type weapons, I'd presume they're designed to be effective against those who use them. In that case, I'd presume their users are large mammalians or reptiles on the order of bear, rhinos, elk, elephants or dinosaurs. Very large, heavy skeleton apex predators or omnivores with fat and muscle layers, likely with dense hide, fur or armored plates. They're likely fairly ponderous in regular life, careful and calculating. In this case their doctrine likely is to scout, locate and strike asymmetrically out of range or from an unexpected direction with precision and then, failing that, to fire for effect, break contact and reset. Continuing to fight after revealing your location and tactical situation is foolhardy because once an enemy knows where you are, you are at a disadvantage and little more than an amusing target. Their engagements would likely be sniper battles. There would be occasional shots. Superior marksmanship, fieldcraft, hunting acumen and the ability to out think and read your enemy would be key. Units would be more like federated hunting parties with blinds, bluffs, ambushes and lures. Battles would play out like a football game over a wider area as each group jockeys for position while protecting their own assets. Being hit anywhere would likely be a fairly high trauma wound and if not fatal, would slow you down and make it harder to think, making you an easier target and starting the death spiral. Shrewedness, calculating precision and personal capability would be fundamental. A weapon is only as useful as its operator.

Whoever would win is whoever could adapt the fastest. Both could win.

The long-range effectiveness of the big bores would catch the light shots off guard. They'd need only a glance and a good guess to rain down deadly fires. The light shots need a way to get in close.

The group assault tactics of the light shots would catch the big bores off guard. They'd only need a few in penetration range, and then a big bore wouldn't have time to get to an advantageous position and sight in. The big bores need a standoff mechanism or a fast response.

The big bores would need to rely on their hunting acumen and inventiveness. If they pivoted on the light shots needing to get in close they could establish a system of interlocking fields of fire so that no approach is safe. All they'd have to do then is sit and wait for their quarry to appear, which they're more than happy to do.

They could also easily convert a large bore weapon to a shotgun and start carrying sidearms to repel close-in assault. An increase in rate of fire and higher capacity magazines as well as patrolling in pairs would blunt the effectiveness of light shot ambushes.

They could prepare static defenses like mines. If the light shots can't get close, they can't be effective.

The light shots would need to rely on their numbers, speed, stealth and inquisitiveness. If they realized the big bores are only effective at range, they'd need to either close fast or start close. Deploying sleeper units in random places to wait for big bores and attack opportunistically, or use their superior mobility (digging, flying, climbing) to come at big bores from many directions at once and directions they don't expect could allow enough to get in range to be effective.

The goal would be to splinter a hunting party in to smaller groups or individuals so they couldn't overwatch each other or respond to contact. They'd then be easy pickings to swoop down on. Randomized tactics would keep the big bores guessing. The assault, once started, should be constant to keep the big bores from taking a breath to plan.

It would not be hard for the light shots to convert captured big bore weapons in to crew-served weapons. If they can pin down a big bore with long range fire, they can easily swoop in and nail it.

As far as exosuits, you may want to lean in to that and have the big bores be human-sized, but trying to fight against dinosaur-sized predators. You may also want to dial it down and have exosuits be more like upscaled smartgun assist armatures the colonial marines used in "Aliens!".

In general, start with why. Why do they have light and fast? It works. Why does it work? It is effective against most of the things they want to shoot at. Why? Light and fast is pretty good at hitting light and fast targets close in. Vice versa for the opposite. You can see how I worked forward from there. What is small and light and effective close in? Insects. Based on their physical stature you can extrapolate tactics and in part the warrior culture, which would effect strategy and ethos.

There are some good answers here on the subject of weapons here so I will respond to your edit about not wanting one side to dominate in the conflict.

Essentially it comes down to numbers. If one side (culturally) only uses elites to fight wars then they will have a lower manpower than the side that gives everyone a gun and says "Advance on the enemy or I shoot you".