Actually, the sheer weight of a blade that size would help to reduce recoil. Anyway, to effectively weild such a huge weapon, you'd need good upper body strength anyway.
[q=DJzen]the gunblade does not actually have a barrel. What Kimera noticed was not the barrel, but rather, spindle that the chamber revolves around. If you look VERY carefully, you'll see the start of a barrel at the top of the gun part of the gunblade. However, the blade itself gets in the way of the barrel. Now, the shotgun idea is a bit more sound, since it's possible that a shell is fired from the chamber, hits the blade and turns into slag, which only does a good amount of damage at close range anyway.[/q]
If the bullet simply got fired into the blade and then disintegrated, this would spray white-hot fragments in all directions. Very dangerous, especially with your hands only a few inches away on the handle. You're right about the gunblade having no barrel... but look at Seifer's weapon. It clearly shows that the bullet is fired to the side of the blade.