Actually, Mass Effect had pseudo-scientific explanations for how the weapons worked. There was a thought process and a modicum of logic applied to the design of those weapons. I can suspend my disbelief at the idea that the world is overrun with zombies while watching The Walking Dead. I cannot, however, suspend my disbelief that a van would fall off a bridge bumper-first, and then land on all four wheels when it hits the ground (as they showed in an episode last season). The accepted reality of the presented universe doesn't allow for that. The same way that the accepted reality presented in Destiny in no way explains how a bullet can "magically" be transferred from one part of a gun to another. Especially when that gun's design is so obviously based on real-world examples. It's an excuse for lazy design. Plain and simple. A strong emphasis was obviously placed on the appearance of the weapons, and little to no thought went into functionality. The irritating part is that it's so hit and miss. As I pointed out in my post, the Hawkmoon is fine. The shotguns are fine. The snipers are fine. If the barrel and receiver on the shotguns must be aligned, then there is no excuse for the Hand Cannons not having barrels and cylinders that are properly aligned. The universe that Bungie created implements the real-world standard with other weapons... so it's not just a case of suspension of disbelief.

You never know. With advanced-enough technology and enough moving parts, anything is possible. While it could never work in modern designs, they might have a very sophisticated way to transfer the shots from the mag to the barrel. For handcannons, while overly complicated, the hammer could trigger a small reaction within the gun that propels the projectiles forward. At the end of the day, it's best to just fall into the side of space magic. Even if it's not currently viable in real life, I would prefer they design the weapons to look good. At the end of the day it's a game, it does not matter how realistic they look. They could have coded a rock to shoot bullets, realism is not needed.