The Tavern

Melee weapons don't run out of ammo.
Spells basically have a per-combat limit that recharges once you get away.
Ranged weapon users can run out of ammo due to bad luck and be totally screwed.

Have we considered straight up making ammo no longer a thing? Unlimited ammo for all.
It's not realistic, but are there any downsides from a balance perspective?

That in itself wouldn't be a valid argument in a game that features flying pigs, among other things.

I think nobody has other arguments than they want a mechanic that is different from both spells, both evocables and both melee.

For an experienced player arrows and bolts are usually enough to kill everything dangerous, if you do not use them on popcorn. Ranged weapons are still superior to melee, and an other reason that they need not to be buffed. Note that they are not week currently, just annoying to swap to melee all the time vs. a week enemy.

This by itself is a solid argument in favor of adjusting the ammo system.

Even without any ammo system, however, ranged weapons would still be different from spells, evocables, and melee. Spells use MP, evocables use charges, and melee features many mechanics not available with ranged attacks, including auxiliary attacks, cleave, and a variety of brands that aren't seen on launchers, barring a few exceptions on unrandarts. Mechanically, the ammo system is just an MP system that recovers faster outside of combat and doesn't recover in combat, with an arbitrarily fluxuating maximum depending on RNG and punishing frequent use. It's completely irrelevant as a limiter on characters who primarily fight and melee and pick up ranged weapons as a secondary option to deal with dangerous ranged attackers, and a source of annoyance and frustration for players that choose it as their primary combat option, training melee as a secondary option solely for the sake of preserving ammo. Even if it were desirable to force players to train a melee weapon to survive as a ranged character, ammo isn't even an effective tool for that, as they can simply allocate that skill xp to a different ranged weapon type instead.

How about setting the ammo mulch rates to zero? (a one-liner change in the code)

Keep the interesting strategic/tactical challenge of getting your ammo back, but lose the risk of being left without any ammo due to bad luck.

Maybe even limit that to unpoisoned ammo, or make the ammo unpoisoned if it hits an enemy.

I think in the early game ammo can provide interesting decisions.
Such as: When do I use my sling bullets? When do I use my preciously branded dart/javelin/wand charge?

I wouldn't be opposed to having bundles of infinite arrows/bolts/boomerangs drop in the mid game. Darts and nets are too powerful to be available in an unlimited quantity.

the AM background is the only situation where I find early game ammo scarcity obnoxious myself.

Could just make stones, arrows and bolts never mulch. Sling-bullet mulching is potentially interesting as petercordia said, and non-stone throwables are balanced around being scarce.

My problem with some kind of ammo not mulching and some mulching is that it leads exactly the kind of gameplay we have now.
Currently you switch to an untrained melee weapon against week enemies to conserve ammo. If there is an ammo that does not mulch but has less damage, you could switch to that against week enemies. So you similarly constantly switching, which I think is highly annoying.

That could be solved by slightly improving the hotkeys.

It's already possible to bind 'fire sling bullet' to a hotkey 'Fc ' (if your sling bullets are in inventory slot c), which is no more obnoxious than binding a hotkey to 'za ' to spam your default spell.

I acknowledge that using a hotkey to fire a single bullet is less intuitive than using it for spells.

On slingers I inscribe stones "@Q1" and bullets "@Q2 !t" then macro '1' and '2' to 'Q1' and 'Q2'; the scheme extends in an obvious way for throwing ammo.