I know this is a late entry, but I stumbled upon this question and it piqued my interest! Guns aren't bad weapons with the base rules, they just seem to require a different kind of investment, like different magical bonuses and special magic items on the side...
Guns are expensive
Being a gunslinger allows you to craft your own weapons for half the price of the weapon. Since you mentioned wanting to use a revolver, it would cost you 2000 gp, as well as 4 days work. This can be compared to a fighter acquiring a suit of full plate armor (1500gp). It's a serious investment, but not one significantly higher than what other party members can expect to pay for their gear.
However, you are going to use those guns in a way that allows you to ignore armor modifiers to AC (within 5 range increments for a revolver, as its an advanced firearm). Ignoring armor is a bonus not unlike that of a brilliant energy weapon, which is a +4 bonus equivalent for a magic weapon.
In the end, as equipment goes, a gun is on the expensive side, but its main quality (ignores armor) is worth a lot more than what you're paying for. It's basically a rip-off!
Ammo is expensive
Is it? The abundant ammunition spell allows, for 1 minute per caster level, to replenish any ammo taken from a container, such as a quiver or a pouch. According to item creation rules, crafting a bullet pouch that refilled itself every time you took ammo out of it (use-activated) isn't so expensive :
- 2000 gp base price (2000 x spell level 1 x caster level 1)
- 100 gp for material components (unlimited charges costs the equivalent of 100 charges, which means 100 bullets worth 1 gp each)
Although the craft wondrous item feat has a pre-requisite of caster level 3rd, the craftsman can elect to cast the spells required for the item at a lower caster level, thus reducing the total cost of the item (included in the above estimate). If your wizard friend has the craft wondrous item feat, he can halve these costs, as you only need to supply him with the base materials. Alternatively, having the bullet pouch cast abundant ammunition on itself for 1 minute upon speaking a command word would reduce the cost slightly (1800 gp base price instead of 2000 gp).
As far as magic items go, this one is pretty cheap considering you'll never have to worry about ammo again! As a precaution, however, I'd recommend buying the spell fabricate bullets for your wizard friend to learn. That way, if you ever misplace your magic bullet pouch, you can still have him create 30 bullets per casting, providing you can find 2 gp worth of metal...
Guns don't add ability bonuses
At level 5, a gunslinger gains the gun training ability, which allows you to add your DEX modifier to the damage roll of one type of firearm. By definition, "pistols" should include revolvers. This is even better than bows, as you only need one single stat to do everything!
I guess that's it for this point: guns do apply ability modifiers to dmg rolls, at least for gunslingers of level 5 and above.
How to keep up with the damage output of other classes?
- Get dexterity augmenting items: Your damage and chance to hit are both dependent on your dexterity. Boosting this stat should be your priority. As a bonus, your AC also goes up!
- Prioritize elemental weapons over higher bonuses: You already ignore armor to hit, meaning you'll hit more often than your friends. Instead of going from a +1 gun to a +2 gun, opt for options like flaming, frost or lightning, which all add 1d6 to your damage. Alternatively, if your campaign is heavily thematic and you encounter mostly one type of enemies, bane becomes a very strong property.
- Use the clustered shots feat: This feat allow you to add the damage of all your shots before applying enemy damage reductions. This will allow your gun damage to stay relevant on higher end monsters. This also allows you to cheese the massive damage optional rule if your GM uses it.
- Use the deadly aim feat: This one is a matter of preference. Deadly aim is like the power attack feat for ranged weapons. However, the firearms rules state that using the deadly aim feat is not a touch attack even if within the proper range. If you can deal with that (you do have high DEX and the best BAB available, after all), it's potentially great damage.
- Get more attacks: By dual-wielding pistols, you can get up to 8 attacks with the proper feats (4 base attacks, 3 for the dual-wielding feats, 1 for rapid shot).
After 2 rounds, my guns are empty! How do I reload fast enough to keep going?
In the real world, speed loaders exist. These devices allow you to load 6 bullets in a revolver simultaneously. You have to pre-load them with bullets, however. But... They're some sort of container, then... or do they not hold 6 bullets? If you can create a bullet pouch that refills infinitely, why not a speed loader? Note that you'll need 2 such speed loaders to recharge 2 pistols, as they can only refill once at the start of each round. With the rapid reload feat, a speed loader should allow you to reload a pistol as a free action, if your GM allows it.