I was thinking of maybe going the arcane archer route to get free enhancements on all my arrows. How exactly does the crossbow thing work though and what books are those classes from? I'm still pretty new at this
"Aptitude" is a weapon special ability from Tome of Battle. The price is a +1 equivalent (that is, a +1 Aptitude weapon costs the same as a +2 weapon, and if you wanted to add more stuff it would be priced as if you were bringing it up to +3 or higher). What Aptitude does is it allows you to use any weapon-specific feats with the weapon, even if the weapon is the wrong type.
For example, a great crossbow requires a full-round action to reload, but because
Hand Crossbow Focus lets you reload hand crossbows as a free action, a character with Hand Crossbow Focus and an Aptitude great crossbow can load the great crossbow as a free action, enabling full attacks and (if applicable) making extra attacks from other sources.
Lightning Mace lets you make a free extra attack any time you roll a critical threat, if you have a light mace in each hand. Because it says a light mace in each hand (instead of saying two light maces) you could make the argument that a two-handed Aptitude weapon is occupying each hand (assuming you only have two hands) and can benefit from this feat.
Roundabout Kick enables you to make a free extra unarmed strike attack against the same opponent, whenever you confirm a critical hit with an unarmed strike. Again, weapon-specific feat, so Aptitude effectively re-writes the feat to say "this weapon" instead of "unarmed strike".
The Great Crossbow is an exotic ranged weapon in Races of Stone. It does respectable base damage (2d8), though this would be garbage with the required full-round load time, which Hand Crossbow Focus obviates. The range increment is 120 feet, not bad. The main selling point, and what makes it a good idea for this build, is it crits
18-20/x2, like a scimitar or a falchion. If you have the Improved Critical feat (or throw money at it to make it Keen like I did for my low level, filthy rich version), that improves to
15-20/x2, and you're threatening critical on 6 out of 20 possible natural attack rolls, IOW 30% of attacks assuming your attack bonus is high enough to hit on a natural 15.
If you're using the Splitting weapon special ability, each bolt fired becomes two identical bolts that each use their own attack rolls, leaving you with a (.7*.7)= 49% chance of
not threatening at least one critical with every shot. That's a coin flip, very slightly weighted in your favor. With each critical threat creating a free extra shot that splits into two, and each confirmed critical creating another free extra shot that splits into two (granted, this is restricted to the original victim, not a new target), and all of these free extra attacks carrying the possibility of threatening/confirming critical and generating even more free extra attacks, you can put out a very large amount of shots with a little luck.
Blood in the Water stance gives you a self-stacking +1 to attack and damage rolls every time you confirm a critical, so your shots get more powerful and more accurate the more lucky shots you make. It's very possible to find yourself in a situation where you've got half a dozen extra attacks going nowhere, because you just killed the whole encounter as a standard action and have run out of targets.
Two other items I should note are really helping me with mine: a Quiver of Lies and a Flesh Ring of Scorn, both found in Book of Vile Darkness. The Quiver of Lies conjures up an arrow or bolt in your hand (whichever is appropriate to the weapon you use) any time you tell a lie, as a free action. This saves you from having to carry a huge amount of bolts, or wasting actions drawing a new bolt case when you deplete a case of 10. The Flesh Ring of Scorn allows you to automatically confirm critical threats against non-outsiders, but it only works if it's pierced into the flesh of an evil outsider. My minigunner just wears it as a septum piercing and is using the Use Magic Device skill to fool it about his race and alignment, and while he's destroying everything in front of him he's yelling "I am a banana!" in Orc the whole time, convincing surviving witnesses that he's dangerously insane.
