In the past some revolvers have been made where the barrel aligns with the bottom of the cylinder not the top and they obviously use a hammer and pin system which is common in pistols. Most of the lmg's I use ingame you can see the chamber while reloading and it is accurately placed. As far as scout rifles are concerned there are some odd loading systems out there for example in the p90 the rounds sit perpendicular to the barrel in the magazine and are rotated into the receiver. Aside from all that it is a game set in the future so.........yeah......