I think I've somewhat covered this in the past in a topic on scale (I recall ranting about how Bolt Action's 24" rifle range, gives them an absolute range of about 50 yards/metres "in scale" - resulting in weirdness such as 28mm paratroopers who could not shoot the length of the Arnhem Bridge model Warlord themselves supply.) I also have looked at move:shoot ratios (how movement ranges compare to weapon ranges; i.e. Bolt Action copies the 6"/24" (1:4) ratio made popular by fantasy Warhammer - which can be jarringly short with modern firearms.
However I've been thinking about it a bit lately and would like to come in from a different angle. First of all, let's look at why ranges are compressed.
Restricting weapon ranges can be done to promote maneuver; short-ranged weapons cover less area, leaving plenty of room to move about without taking severe casualties. In a 2:1 game (say 12" movement, 6" shoot) maneuver is very strong - units can duck in and out of engagements almost at will. In a 1:12 (say 4" move, 48" shoot) then the firepower tends to dominate - it's hard to move out of range or close with the enemy without being shot to bits. Units will probably camp in cover.
This obviously is much impacted by the lethality of weapons (the chance of death per attack; a typical 40K-esque roll of 4+ to hit, then 4+ to hit has a 25% chance of causing a casualty and I often use this as a benchmark) - if it is a '6' to hit with a '6' then required to kill (5%?), maneuver is unlikely to be impeded as death would be caused more by luck than firepower. This is lethality is multiplied by "rate of fire" - attacks per turn - I assume a RoF of 1 for a baseline; but 2 or more is possible with many weapons, and likely with modern warfare.
Terrain and Weapon Range
While playing with my homebrew Tankmunda, I was struck by how much of a role terrain plays in this as well. Using 15mm (1:144) tanks on a 6x4 table, I didn't want engagement ranges to look silly and nerf-gun short, yet I wanted differentiate between the long range capabilities of say a 88mm and a 2pdr. I also did not want tanks able to hit each other from the very first turn shooting between deployment zones. If I kept the ranges strictly to scale, ranges would be unlimited on the tabletop - a route increasingly taken my many games. Even assuming a 2-3" long tank is say 5-6 metres in scale (2 metres per inch); a 1500 metre gun range would reach 750 inches or 62 feet... a tad longer than most gaming tables...
My solution was to compress ranges as much as I could without them visually looking silly, but also to ensure there was terrain every 8-12" (the distance of the "sprint speed" of most tanks). And I was thinking - how often do wargames specify how much terrain or how it should be set up?
Not often. I do know Infinity is very specific. It has higher than usual lethality (30%+) with a high rate of fire (3+) for most weapons; an attack on a unit in the open is very very lethal. Move:shoot favours shooting with 4" vs 36" for normal rifles (many reach across a table) giving a 1:9+. Infinity wisely has detailed setup instructions. Setting up a table like traditional 40K (with 3-4 terrain pieces and much wide open space) will see everyone dead in short order. Sight lines must be kept short (8-12") - even a single tall building can offer a massive field of fire, completely unbalancing a game.
Obviously, the "traditional" 24" shooting range for a 28mm figure assumes little cover; and is handy for a gamer with little terrain. Like a typical 40K table. Games like Infinity with very lethal, long-ranged weapons demand a huge investment in terrain or the game is very un-fun. That said, a WW2 game where bolt action rifles shoot as far as a garden hose look silly. Warmachine (admittedly steampunk) even has sniper rifles with 14" range (vs handguns that shoot 8" or so). Yikes!
But what can we do to mitigate this? How can we make it so weapons shoot further without messing things up? Well, weapons can have their lethality tuned down. Want to double ranges to 48"? Make it so it hits on a 5+ and kills on a 5+ on a d6; now instead of 25% chance of killing per attack, it's more like 10%. This compensates for the doubling of the range. Maybe units can be stunned or suppressed; instead of outright removed.
It's all about terrain, baby
However I'd like to focus on terrain (or lack thereof). On the importance of making it clear how much terrain is expected - how far apart, and the impact of the terrain. I'll assume that being in cover gives a 4+ d6 (50%) save. If terrain is no farther apart than the average unit move (say 6") we have effectively halved the lethality of the weapon (down to ~13%). We could double firing ranges with no major issues. If terrain is farther apart than units can move in a turn (say 12"+) then lethality is less impacted (it will also encourage camping).
The effect of cover (modifier to "to hit" or saving throw) is also worth thinking about. If we assume a 4+ (50%) saving throw for the average cover - what effect would a 2+ (83%) save have? It would confer near-invulnerability on units and discourage them from ever moving. In contrast, a 6+ (17%) save would make the cover barely worthwhile. This ties with rewarding and punishing players; using saves and modifiers to direct them in the way you want them to play.
Weapon ranges, movement distances and the lethality of weapons are all used as balancing methods. They dictate particular playstyles and most game designers adhere to pretty common formula. This can result in silly looking games (modern rifles shooting the same range as bows or slings; the average elf archer would handily outrange a Bolt Action grunt with a Mauser).
Terrain however is also a major balancing factor with as much impact as any of the above methods. And few wargames rules actually address this. How much terrain? Where? Even - what effects does the terrain have - many times terrain modifiers seem to be copied-and-pasted regardless of genre. Should "cover" (and it is often genric; or divided into "soft" and "hard" at best) have the same 50% save to a M60 as it does to a sling? How often is terrain actually addressed in rules.