Destiny is a space game set way way in the future. Halo is set in the much nearer future. Research and stuff between now and 5 years could develop any sorts of guns and stuff like that. So.. the next maybe 250 years? I'm sure there will be many more developments. 150 years ago.. the idea of Full auto weaponry or gas powered weaponry was impossible. Just like right now the idea of everything that we believe is supposed to line up not lining up is impossible. So.. you can't say it isn't realistic until we are in the time that the game is set in. Let's just go with destiny's timeframe being 300 years in the future.. imagine what kind of research developments could happen between now and then. Nothing is impossible. Yes. For right now it's not realistic. But.. ask yourself. Was it supposed to be realistic? Maybe bungie broke that law of realism because they can. It's a science fiction game! It was not meant to be realistic.