Since the Antigua line weapons are actual revolvers that shoot piercing, I think that the gun should have real-time bullet-by-bullet reloading.

How would it work?
Every time the gun goes into its idle animation, if it has less than 6 bullets in it then your character will start reloading.

How would it be different from reloading on other guns?
While it would maintain the passive reloading style that this game has, it would be incredibly different from normal guns. I am thinking of the following things:
1. Instead of making the player slow down or stop to reload, they would reload bullet-by-bullet in real time at their normal movement speed.
2. Because of the real-time reloading, reloading would be a lot more tactical. It would take a lot more thought than "fire five shots, wait a few seconds, then fire five more to skip the reload" or just mindlessly shooting all your bullets. The player can shoot a bullet, let it reload, and then shoot again, or shoot all six bullets and wait for the full reload, or fire in any other number of patterns. Players would also not need to wait for a full reload to start firing their gun.
3. The reload would not be able to be skipped.
4. Reloading would take roughly 3 to 6 times longer on this gun with this change than it does now, but again, it doesn't slow the player down.

How could this be balanced?
The Antigua line weapons could be powered up to compensate for the longer reload times. I don't know what actual numbers to go with here, in terms of both reloading speed and bullet damage, but I'm fairly certain this could be balanced.

If it ain't broke don't fix it... why implement this?
It's one small change that will add a LOT to the game in the way of variety. There's nothing wrong with the Antigua line weapons right now, but I think a change like this would be all around good. It would create a more "gunslinger" feel to the weapon, and make it feel more like an actual six shooter and not just a faster version of the Blaster with double the clip size. It would add that much more to set the Antigua line weapons apart from other ranged weapons, and variety is the spice of life.