This is how the weapons work in the FoG games:
- Slings are always in 240 man light infantry units and always have a range of 2.
- Infantry bows come in 240 man light and 480 man massed units, both of which always have normal range of 2 and long range of 4.
- Mounted bows come in 240 man cavalry and 120 man light horse unit, both with range of 2.
So in short: at short/normal range, bows and slings are considered equal, but any foot archer is capable of shooting twice as far with reduced effect. The last bit is what I find most questionable.
-Historical bow and sling-
Here's a nice compilation of quotes from various sources that someone made on Total War forums back in 2013 regarding slings: https://forums.totalwar.com/discussion/ ... f-slingers
Here a particularly interesting bit from Anabasis, describing the retreat of the 10 000 Greek mercenaries from Persian Asia Minor in 401 BC:
Here are the same bits from slightly different translation: https://www.gutenberg.org/files/1170/11 ... k2H_4_0024[3.3.15] For at present the enemy can shoot arrows and sling stones so far that neither our Cretan bowmen nor our javelin-men can reach them in reply; and when we pursue them, a long chase, away from our main body, is out of the question, and in a short chase no foot-soldier, even if he is swift, can overtake another foot-soldier who has a bow-shot the start of him. [3.3.16] Hence, if we should propose to put an end to the possibility of their harming us on our march, we need slingers ourselves at once, and horsemen also. Now I am told that there are Rhodians in our army, that most of them understand the use of the sling, and that their missile carries no less than twice as far as those from the Persian slings. [3.3.17] For the latter have only a short range because the stones that are used in them are as large as the hand can hold; the Rhodians, however, are versed also in the art of slinging leaden bullets. [3.3.18] If, therefore, we should ascertain who among them possess slings, and should not only pay these people for their slings, but likewise pay anyone who is willing to plait new ones, and if, furthermore, we should devise some sort of exemption for the man who will volunteer to serve as a slinger at his appointed post, it may be that men will come forward who will be capable of helping us.
[3.4.15] But when the Rhodian slingers and the bowmen, posted at intervals here and there, sent back an answering volley, and not a man among them missed his mark (for even if he had been very eager to do so, it would not have been easy), then Tissaphernes withdrew out of range with all speed, and the other battalions followed his example.
[3.4.16] For the rest of the day the one army continued its march and the other its pursuit. And the barbarians were no longer able to do any harm by their skirmishing at long range; for the Rhodian slingers carried farther with their missiles than the Persians, farther even than the Persian bowmen. [3.4.17] The Persian bows are also large, and consequently the Cretans could make good use of all the arrows that fell into their hands; in fact, they were continually using the enemy's arrows, and practiced themselves in long-range work by shooting them into the air. In the villages, furthermore, the Greeks found gut in abundance and lead for the use of their slingers.”
TL;DR: The Cretan Archers were out-ranged by Persian slingers (with large stone projectiles) and archer (with larger composite bows), which were in turn out-ranged by Rhodian slingers with lead projectiles. It's also particularly interesting that the Cretan archers initially couldn't match the range of Persians and "practiced themselves in long-range work", even though they were regarded as some of the best archers of Mediterranean world and allegedly out-ranged other archers in the region.
The translation on gutenberg is a bit different on the details, saying the slinger outranged some of the archers and it's a lot more ambiguous whether the Cretan archers were training just to get the feel for shooting at long range with the Persian arrows specifically or long range shooting in general.
I think the most interesting takeaway here is that the range of sling and bow varies a lot depending on not only the weapons* and the skill of the shooter, but also the specific training and/or experience of the shooter. Physically sling with a lead projectile could have better maximum range than bow: the bullet has inherently lower air resistance, flatter trajectory and is effected less by the wind (or archer's paradox). Ultimately both weapon types are limited by the skill of their user more than the mechanical details of the weapon. These skills are not something you can just learn in couple weekends and pretty much all of the groups famous for their skills with bow or sling came from cultures that had an institution for training those skills extensively. Cretan Archers, Rhodian Slingers, Balearic Slingers, English/Welsh Longbowmen and Mongol horse archers trained their skills extensively from young age even in peace time, which is the main reason they were so deadly with their weapons. Javelin, crossbows and early firearms also likely owe their popularity to requiring less training to be effectively usable in combat compared to the sling and bow that could likely still outperform them in various ways thanks to their higher skill ceiling.
(* Bow could be anything from short self bow to advanced composite design with arrows of varying characteristics, and slingers could throw anything from large stones to cast lead bullets with slings of varying length and construction.)
In Anabasis the Cretan archers, despite presumably being highly skilled light infantry, didn't seem to be that familiar with long range shooting. If you trained archery primarily as a weapon for hunting (or skirmishing against javelinmen) that would make a lot of sense though, you don't shoot indirect arching fire at a rabbit at an extreme range like you might at the enemy formation. On the other hand some less skilled military archers might have been drilled to do just that kind of longer range shooting with less emphasis on precisely hitting a specific target. Slings, being very simple and cheap weapons to make and use, have been used by all kinds of people from medieval camp followers and poorly trained mobs (which in practice would be shooting in the enemy's general direction with very limited practical range), to professional warriors like Aztecs who were a real threat even against late medieval armor (unlike their javelins and arrows), or the Balearic slingers with several different slings and projectiles for different ranges and situations.
In general my impression is that both bows and slings have pretty similar range of possible effective ranges (with the ballistic advantages of sling most likely being negated by it arguably being a harder weapon to aim). Good slingers would generally out-range poor archers and vice versa. In a match-up between similarly skilled archers and/or slingers the mechanical minutiae of their weapons and the exact nature of their training/experience might play a more deciding role. By various accounts the damage and "anti-armor" performance of the two weapon types also seems to have been varying but comparable (i.e. insignificant in FoG2's top down design).
-Current FoG2 situation-
So getting back of FoG2. This raises the questions, why do all infantry bows have the 3-4 square "long range" when slingers and mounted archers don't? Why do light archers always have that long range even though they would often be hunters or even levies by background and armed with relatively weak bows, when the similarly sized horse archer units who in many cases are professional warriors armed with notoriously strong composite war bows don't get that extra range? Why do slingers inherently lack the long range even though there's little reason for the difference considering the least skilled slingers (and archers) are likely considered to be part of the peasant/rabble units or non-combatants, so any dedicated slinger units should be at least experienced with their weapon. The current gameplay differences of bow and sling units just seem really arbitrary for a wargame that is otherwise very consistent and actively avoids creating meaningless or arbitrary differences where possible.
-Simple suggestions-
To me it seems like there would be two simple ways to make the missile troops more consistent: First one would be to give both the light slingers and (non-light) horse archers (since the light ones don't really have enough firepower to reduce from) the same 3-4 long range as foot bows. This would make the horse archer armies a bit more flexible when it comes to shooting. It would practically make the bows and slings identical but that is arguably more realistic than the seemingly arbitrary difference that they currently have.
The second way, and the one I'd prefer out of these two, would be removing the 3-4 range from light foot bow which would leave just the massed archers with the extra range. This would generally make a lot of sense but it would be a bit of a slap to the face for some units like the aforementioned Rhodian slingers and various expert bowmen with historically good range, and it would still leave a lot of massed archer units which probably don't really deserve the extra range (often being essentially nerfed light foot for the sake of game balance rather than being a formation from historical doctrine).
-Bigger suggestion-
Outside of those two options there would be a more complicated option of making the "long range" shooting capability experience dependent. Bow and sling armed units with experience level higher than average (or maybe higher than above average) would get the ability to shoot at long range (possibly excluding the light horse archers), the average or worse units would be limited to the "short" range of 2. The big benefit of this would be that the extra ability would be targeted at units that most likely deserve it like elite slingers/archers and professional mounted warriors. It would also make the increased cost of high skill missile units bit more appealing, as currently the minimal difference in raw damage doesn't really feel worth it.
The iffiest effect would be that massed bow units would generally lose the ability to shoot at long range while the superior elements of horse archer armies would gain that range. This would likely mean a slight buff for the horse archer armies overall as it would reduce the reach of their biggest threat and allow them to more consistently (and realistically) shoot back at a unit that they have just evaded. If I'm not missing something the horse archers' firepower at long range would be similar to that of light foot (plus whatever the often superior skill level would add) so there shouldn't be excessive amount of pointless shooting with low ammo. (It might actually even make sense to turn off any unit's ability to shoot at long range if they are on low ammo since it doesn't do much, slows down the game and they presumably should be saving ammo by that point.)
In FoG2 medieval I'd leave crossbow and longbow as they are with any unit armed with those being able to shoot at long range regardless of skill level. It would give crossbows (and longbows) a range advantage against regular bows (excluding professional warriors and such) and keep them a threat to all horse archers, which all seems to fit well with what I have read and heard on the subject.