I'm tellin' ya, magic...

I'll say again that I don't have a convenient pic of the hyperion handy, so I can only speak for the revolver. The revolver clearly has no barrel. However, if it did, firing a bullet straight forward would be pointless. While the revolver has a pointed tip, it is clearly not designed for thrusting. It has a huge blade that is clearly made for slashing. Regardless of the designer's intent, Squall slashes with it.

Why does this matter? Because slashing forces the blade's end to point upwards, AWAY from the object being slashed. This would mean the barrel of the gunblade would also be pointing away, causing the bullet to go flying off into the distance. The only way for the barrel (assuming one existed) to be pointing toward the object would be to thrust with the blade, putting the end of the barrel INSIDE the enemy. I've heard jamming a gun is a good way to wreck it. Even if it didn't, Squall never thrusts with the revolver, he only slashes with it.

The way I see it, this can't NOT be explained by magic.

BTW, I'd like to see pictures of some of these original gunblades if anyone can point me to 'em.