Shell Guide

Advanced Cannons and some simple weapons use custom shells designed by players through Ammo Controllers and customisers. Making the right shell for your gun's role and gauge can be difficult as the sheer number of options is staggering.

Due to the increase of people asking what kind of shell they should use with their gun that has X and Y stats, here is a guide to help you pick. Before you read, do note that there is no all-around best shell. The best shell for your gun is one that is also optimized for the armour and defenses of your targets.

Selecting a Shell Type
Please start by considering the table above. Note that shells that require high rates of fire will typically be quite weak with smaller gun designs. As such, you will need to either bring a lot of those guns or be patient for them to deal significant damage. However, you should also bear in mind that a higher gauge system, while it will be more impactful per shell, will be affected much more if your shots miss. As such, a small APS system with a high gauge shell should probably have special considerations for accuracy and shell speed.

Bigger and more expensive guns will have more freedom to field more versatile shells and/or less reliable shells due to sheer volume of fire.

Kinetic
Kinetic shells need to be accurate. A miss is a 100% loss of damage for these shells, unlike timed flak for example. As such, fins and tracers may be worth considering, especially on multi-barrel or for longer range engagements. Kinetic shells also tend to be somewhat short and have plenty of gunpowder and possibly railgun assist as muzzle velocity means more damage on top of less travel time to the target (indirect improvement of accuracy).

The value of a kinetic shell is usually calculated by multiplying the AP value of the shell by its kinetic damage (KD). The higher the result, the better the shell. By design, higher AP shells have less kinetic damage, but overall a better AP * KD ratio. This is because any excess AP beyond the AC of what you're hitting provides no benefit. As such, it is important to have an idea of how much armour your targets will have on average when designing these shells. A shell that is worse on paper in terms of AP * KD will still be better if it has enough AP to deal full damage and more KD than another shell.

Sabots have the best AP and AP * KD ratio, but the lowest KD overall, followed by armour piercing, and heavy heads have the worst AP and AP * KD but the most KD overall.

In terms of gauge, both extremes are usually best: either very high gauge or very low. This is because low gauge allows for an extreme volume of fire, dealing consistent damage to an area while very big kinetic shells will be able to pierce significant amounts of armour. In comparison, a medium sized shell may not penetrate the target fully and the reduced rate of fire may mean that you will not get to land a second shell in the same spot to deal lasting damage. Smaller shells get around this by spreading their damage consistently, weakening an area more evenly over time.

Thump
Most of what applies to kinetic shells applies to thump. The main difference is that thump will never pierce a target. It will always grind the armour, regardless of any stacking bonuses. Thump shells also do not care about about the angle of impact and never ricochet, effectively provided a mix of damage and the equivalent of an inertial fuse in a single - but full length! - module in the case of hybrid shells.

APHE
Sometimes referred to as a "pendepth shell" because there are variations to APHE but all require a pendepth fuse to work properly. The concept here is to build enough kinetic damage and AP to pierce a certain amount of armour and then trigger a payload inside the target. This is usually done by using an HE or frag warhead.

These shells usually need to be quite long in order to fit in both a lot of gunpowder and solid bodies to generate the necessary damage to penetrate the target in the first place. Shells can be made shorter, but this will usually require a railgun setup to maintain effectiveness. In fact, APHE shells are very good candidates for railguns since the individual shells are usually quite powerful and require less rate of fire to be effective, but need a lot of speed to make up for the inclusion of non-kinetic modules.

Generally, any more than 1 or 2 HE or frag module per shell will make it very difficult to penetrate heavier armours, but such a payload is typically sufficient to deal crippling damage on a good hit.

HESH
HESH shells are typically not hard to design. Speed does not affect them beyond making the flight time to target longer which is bad for accuracy but does not affect the damage of the shell. HESH shells explode on contact without inertial fuses and deal a small amount of thump damage like hollow points. HESH is best used against vehicles that do not have Spaced Armour and have thin layers of metal, alloy, or heavy armour as their main protection. However, due to their mechanics, they are still quite consistent across the board.

The main question is whether to go full special factor on the HE modules or not. A lower special factor means a bigger explosion on the outside and less spalling damage on the inside. At lower gauges, the explosion will be worse simply due to the range. At medium gauges, it will depend on the shell length and personal preference. On large shells, a lower special factor can be nice as it will still create a significant amount of spalling and a fairly big explosion that can destroy fragile blocks over large areas.

HEAT
HEAT works similarly to HESH in that it also detonates on impact without the need for a fuse and it can also create fragments past the target's initial layers of armour. Spaced Armour also protects from HEAT. However, HEAT's damage is consistent regardless of how much armour it had to penetrate as long as it has enough penetration metric to penetrate the target in the first place. Its fragments tend to be weaker than HESH, but they are created in a much tighter cone which can make it easier to get past internal armour.

Typically, a penetration metric above 10 will penetrate through 2 to 3 meters of metal quite reliably. A penetration metric of 20 or more is able to penetrate almost anything in the campaign. As for the special factor on the HE modules, it works similarly to HESH. It's usually not worth using a low factor at smaller gauges, it's a significant but potentially good tradeoff for medium gauges, and definitely worth considering at higher gauges.

Flak
I am lumping most timed explosive shells together with flak as their purpose is usually the same: shooting down small planes and missiles. In this case, small gauges are preferrable for shooting missiles unless you have a massive gun as rate of fire will be extremely important. Medium gauges are usually best for destroying small planes as it will have a good mix of rate of fire and damage which the smaller shells will lack. Higher gauge timed explosives are a bit awkward to use as the lower rate of fire will make them less practical for conventional uses. That said, you can definitely use timed fuses on big explosive shells for ship-to-ship combat to transform a near miss into at least some damage.

Hybrid
Hybrid shells are typically worse than specialised shells, but will benefit of extra versatility. Historically, hollow points were often used with things other than solid bodies and sabots, but since their AP has become dependent on the rest of the shell composition, you will need at least some amount of solid bodies to make them worthwhile. At larger gauges, it may be better to use an inertial fuse as the fuse will take up considerably less of the shell's length as gauge increases.

It's also possible to use heavy heads and armour piercing caps on other shells for a bit of added kinetic damage and possibly better shell speed. In that case, you may want an inertial fuse to make sure any explosive or frag payload detonates even if the shell ricochets.