This may sound like a lazy explanation for the guns themselves but all the ammo is actually glimmer. Fabricated by your ghost to fit the weapon you're using. Kinda sounds like another form if space magic but it is lore based in destiny's universe.

Ok so I can answer all of this so quickly your head is gonna spin are you ready? IT'S SCIENCE FICTION GET THE -blam!- OVER YOURSELF! It's not real life. None of your comparisons matter nothing you are bitching about matters none it. It's a game set in the future something none of us have any actual knownledge of so how the -blam!- can anything about the weapons bother you? For all you know we could have guns that do everything in this game but you don't know and neither do I but I'm not sitting here bitching about real life to fantasy land. Are you going to play final fantasy next and complain that some of the swords can harness the power of water or fire? No? Why because you used your brain and realised "holy shit it's a game and the creatures can make whatever the -blam!- they want because it's their game and not mine". But I'm sure tons of people are going to bitch at me saying "well if they didn't want any of this they shouldn't of put it into a book or whatever" hey guess What? People write sci-fi books all the -blam!-ing times and anyone with a brain doesn't stop and go "ummm how can they get shot with a laser beam wearing no actual armor just cloth and not die that's not realistic". Do you know in this weird sci-fi world their cloth isn't laser proof? No? Then stfu and either play the game, read the book or don't do them and bitch about "realism" in something that is sci-fi that's most idiotic thing any person can do and that's why we still have people saying violence in video games creates murders because people like you want to compare them to real life and you shouldn't because if you can't see the differences in them then you are either a naive kid or a very stupid adult.

While I respect your frustration I think you're overthinking this.

On hand cannons, the thing being loaded isn't a round, it's a power load; essentially, the entire mechanism of the internal portion of the cylinder is contained inside of it. The external cylinder wall is just a guide and guard, responsible for aligning, rotating, and protecting the mechanical portion. So inside of the power load, there is a set of wells, and a bullet in each. How the hell the firing pin is supposed to contact the primer is beyond me; maybe it's a caseless-type round that is chemically or electronically triggered? Keep in mind we have a ghost that can alter the electrical and mechanical functions of objects, so that may be part of the intent. Thorn is a little different, it uses hive ritual and universe logic to generate it's projectiles (the story of how Thorn was made is actually really interesting). In short, a gun called Rose was taken into the pits on the moon, and used to fight the Hive while studying their magic and reality structure. The holder then essentially defied all convention by applying the Hive rituals and pieces of Hive bodies and various bones to Rose to augment it and make it function according to the Hive logic and reality structure, rather than our own. It changed the weapon so much it is referred to as a Weapon of Sorrow. Similar to how the Hive crumble when they are physically killed, the weapon does the reverse; it expends a Hive energy charge, which manifests itself as a piece of corrupted carapace when it exits the gun (and it's theoretical personal 'throne world'). This perversion of both the Guardian conduct and the Hive life cycle earns it the title of Weapon of Sorrow quite well (along with its tendency to devour the Light from targets it impales). Omolon guns...the theory on them is that they are firing a highly pressurized jet of a specific fluid, similar to a water-cutter jet, but at a longer range and higher velocity. the physics of this is a bit iffy, as the jet would rapidly lose both force and velocity once it exited the compression vessel; it's possible there is some property of the fluid that is supposed to solidify upon contact with the air and form a proto-slug, but I think the physic of something like that is beyond weak, for realities sake. Something similar to an ionized fluid that follow a primer beam? The world may never know, I just assume it fires Listerine charges and kills things by freshening their breath. Either way, the Vanity is still a PvP favorite. With scouts...yeah, I wondered about that one myself. Unless it's a vaccum-fed system, which has it's own set of complications, the mag placement is a complete mystery for me. I can't even begin to think of the mechanism that would be required to get one of those rounds to battery, and I have a degree in mechanical engineering, for -blam!-s sake. Like the guns, baffled by the mechanical logic I'm being asked to assume.

Shotguns: how do they not even tickle you at a range greater than 15 feet? Snipers: why is ammo capacity so limited? Swords: they require ammo? Sidearms: why isn't full auto a perk you can have? Hand cannons: effective range of how much again? Compared to any real life equivalent? Come on bungie, I shouldn't even have to think about loading my guns with viagra because clearly they are experiencing some performance issues.

This was brought up in a post a couple years ago but not like I'll care to remember the details, but a lot of destiny guns were based off [url=https://en.m.wikipedia.org/wiki/Bullpup]this[/url] it seems

Well this is in the future 😉