Yeah, we don't know what the giant sheaths are for Zenos's swords and that you can see the barrel-like design, but that doesn't necessarily mean it actually does anything other than hold the swords.
We've also seen a gunhammer wielded by Nero in regard to other gunfusion weapons. However, due to the varying types of weapons fused, being of all types of sizes, I don't really see the reason of pointing out the
sword Thancred has is different. It makes sense in size if gunblade is actually a tank class as rumored (ugh, I hope not, but it probably will be with my luck; all sword classes are tanks with exception being samurai). Even then, it still falls in line with
Squall's gunblade in size comparison.
Also, only one side? I don't understand that part of your comment. Garlean gunweapons seem to be based off of revolvers, which the barrel is seen on both sides of the weapon.