I'd advice not messing with the rules at all. especially if your reasoning is that its not realistic. the rules are the way they are for a reason. and if you mess with them you'll unbalance the game. (not that the game is perfectly balanced as it is)
You don't want to weaken the class so that your player is at a disadvantage to the other players. and I also don't think its fair to ask a player to learn a whole new weapon system just for your game.
I used to re-enact Civil War and Revolutionary War, so I have loaded and fired original and recreation flintlock, percussion cap, and breech-loading firearms. I have also witnessed and assisted in the loading of smoothbore and rifled cannon.
All of the literature I can find on top of my own experience states that a good soldier should be able to fire 3 aimed shots per minute. Four shots would be incredible. There are simply too many steps to shorten this process.
These are not at all useful things to compare to gameplay, not just in pathfinder but in general. Playing a fantasy rolepaying game will almost never reflect accurate or realistic portrayals of combat.
Keep in mind, that just because something in Pathfinder is called a musket and uses black powder to fire ammunition, does not mean that it is at all the same thing as our modern muskets. Just like a lot other small things people can point out (just look at all the conversations about long sword-->arming sword).
Long story short. Don't do any of this. The gunslinger is not a gamebreaking class and his ability to reload more quickly than a 19th century soldier should not affect what he can do at your table. If you really hate the flavor of the class, you can ban it; lots of people do. But don't let him play a class and then gimp it to the point of uselessness because you want more "realism" in a game where people can spit acid out of their mouths or point fireballs into existence.
I second the "don't change for realism" Either play with the guns as is or drop guns entirely. It'll be easier for you and end up better for the player.
*I had a GM that said it was okay to play a wizard in his high level campaign. Then when the GM saw what my wizard did in 1 fight suddenly all the enemies had SR 40 and a poor save of 50. Would have much rather been told "NO" at the start then "Yes, but..." and have it change so much that it was no longer any fun.
EDIT: and if you're issue is with guns there's the bolt ace archetype that works pretty well.
Early fire arms should not if accurate to history be any good or useful to an adventurer type, they are vastly inferior even to Civil war vintage weapons.
However you can either make them useful with something similar to the current rules or have pc's not use them.
Your suggested rules say to me use a gun and be useless, instead use a longbow (or crossbow with bolt ace), which is fine but just tell the player that.
The ROF for a Longbow is equally unrealistic when you work it out for high level characters.
Or maybe if realism is that important just skip to giving the pc a revolver or breechloading rifle so that the game effects are closer to 'realism' without making guns useless.
It'd be kinder to just tell your player "no". Your player probably does not want to use a terrible weapon, even if he thinks guns are cool. If he can see how terrible your houserules make firearms, he will either say no, or feel compelled to go with it anyway so you don't think he's a filthy optimizer. If he can't see how terrible you make them, he will feel conned when he eventually figures it out.
And it's okay to have either no firearms or unrealistically good firearms in a game with fireballs and dragons. Pathfinder is not realistic. Not even the parts that look realistic-ish. For instance, if you're experienced enough, you are guaranteed to survive falls from terminal velocity. Your combat capability doesn't degrade at all until you are literally dying (or at 0). High strength characters possess superhuman endurance as well, based on the amount of weight they can carry around all day without fatigue. Your familiarity with Civil War firearms leads you to say "Pathfinder firearms are unrealistically non-exotic and non-unwieldy". Unrealistically wieldy, perhaps. My familiarity with physics, biology, and live combat leads me to say "hell with realism, it's not worth it".
Well, considering just about any monk with the run feat can beat world records for the 50 yard dash, I wouldn't be too concerned with PCs having supernatural speed at the very thing their class is meant to excel at. I would warn to be careful with modern firearms, but that's really about it. The latest errata to double-barreled weapons resolves most of the issues with the flurry of deadly aim bullets in a surprise round, so I personally think its in pretty good shape now.
If you want a realistic game, this isn't it. This is supposed to be an over-the-top, high fantasy game that features fun over realism.
People give examples of wizards and stuff but the non-magical folk are just as unrealistic. A 1st level human who concentrates on acrobatics (18 dexterity +2 for racial bonus (+5 dex bonus to the skill), Skill Focus: Acrobatics (+3), 1 skill point in acrobatics, Rice Runner trait (+1), class skill (+3), Run feat (+4)) is getting a +17 to acrobatics for running jumps at first level. With that they can do a running long jump as much as 37 feet, 11 meters. The world record is 8.95 meters. That same score can get them a high jump of 2.5 meters. The world record is 2.45 meters.
A 3rd level human monk or 1st level barbarian has a move speed of 40. With the Run feat, they can run 200 feet in 6 seconds. That's the equivalent of a 40 yard dash time of 3.6 seconds. 4.3 seconds is considered very fast by professional football standards. He'd do a 100 m dash in 9.75 seconds. The world record is 9.58 seconds and the world record for a woman is 10.49 seconds. So a 3rd level monk or 1st level barbarian would be an Olympic class runner if male, world record holder if female.
So, throw away realism and let your player have fun.
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You have two options with regards to firearms.
1. Make them realistic
2. Make them balanced with other options, which are not realistic. Bows cannot can be fired several times per second unless you are a trick shooter with a piddly little bow that barely does anything. Nor can human targets survive several bow hits from a massive composite longbows, by the way. The unreal-ism lies at both ends of the targeter-targetee relationship.
If you go with the first, nobody will use PF firearms because they are competing with bow users that are firing longbows like they are Lars Anderson with a super low draw modern bow. On top of that, in PF guns and their ammo are hideously overpriced compared to bows and crossbows, costing about as much as a peasant makes in a few years, in the same region as a full suit of armor, and by default they are even harder to use than bows for some insane reason(exotic vs martial). Oh yeah, and you have something between a 1 in 20 and a 1 in 4 chance depending on gun and ammo for your weapon to outright break when you shoot. Happens again, and a weapon that costs the equivalent of hundreds of thousands of dollars explodes in your face. For these reasons, you will not see anyone using pre-advanced guns unless they highly specialize in them. If they specialize, then guns need to compete with other ranged options. That means bows. Guns are actually a little on the weak side compared to bows at the moment(due to no double barrel shenanigans any more), and that's with getting a shot off every couple of seconds...and you want to massively cut down on a gun user's rate of fire to 1 shot every two rounds at best? Really? Adding in the rifle butt and double weapon thing does not help, by the way. Pick up Quick Draw, and anyone can do the same with a heavy crossbow...except it is far cheaper...and there is no chance of your crossbow randomly breaking. And I don't see anyone doing that. Because it's stupid. If you want to hit things in melee, devote resources into hitting them in melee. Don't go half way by spending feats and other resources on using a gun and then only using it as a gun for about 10% of a combat.
If you want to change mechanics in a major way, you need to understand what impact your changes will have or you will screw up parts of the system badly. My suggestion is that before implementing any houserules, go run numbers on how the new rules hold up. For your gun rules, compare a gun user to a normal bow user. If you intend to force gun wielders into melee, compare them to melee combatants. I am talking about DPR calculations by the way. Go run the average numbers, find out for yourself that your changes make shooting a gun crappy compared to picking up a greatsword, longbow or just clubbing the enemy with the loaded gun's butt, and then realize that your realism changes are making an unrealistic system less fun.
EDIT: I guess there is a third option - rewrite all the other unrealistic things that significantly affect the value of guns. And all the things that affect the value of those things...if you want to completely overhaul large chunks of the system, then you might be able to make it work while keeping the system somewhat realistic. But the system wouldn't be Pathfinder at that stage. I would recommend finding a new system at that stage, because it's less effort than hammering in the square peg called Pathfinder into the round hole of realism.
If you want realism Pathfinder is not the game for you. Many of the things a Pathfinder character routinely does are impossible in the real world, especially at high level. Do you similarly nerf other classes due to realism? The current world record for the long jump is a little over 29 feet a 5th level monk with a 10 DEX can easily beat this record without spending any Ki. A 1st level raging barbarian can totally destroy a 2 inch thick oak door in a single blow. Spell casters are even worse.
Unless you are going to nerf all characters equally because of realism don’t nerf any. If you don’t want guns in your game that is fine, but if you are going to allow it then accept it is not going to be realistic.
My realism approach more focuses on the whole AC targeting thing but if you want to do that with your changes, I recommend a way around the long load times besides cartridge+RR or the quick load Wondrous Item (forget which one it is) that would be pricey until at least level 5, like dropping standard ammo but making (alchemical) cartridges more expensive or magic items that would reload for you once per round functioning like the Figurine of Wondrous Power (slate spider) but with reloads.
If you're going to change the game mechanics for gun, this will not be a good or useful change that you're proposing.
All your proposing is how to not make anyone uses guns in your game. They will instead use bows, and be almost as good as if they had used guns.
The real problem with guns (IMO) is the touch AC mechanic. While it is a nod to realism, it's also a problem when you look at the game mechanics. Enemy Touch AC is the one thing that goes down (on average) as characters get higher in level, because monsters get bigger, have lower dex, and rely on natural armor to save them.
This allows a gunslinger to take virtually every to hit penalty available to him to get more damage or some special effect.
Personally, my house rule is to remove misfire chance and remove the normal touch AC mechanic. Things like like Deadeye still work to allow touch AC shots (though it costs grit) and I don't allow the cost (for these kinds of feats) to ever be reduced with favored deed (or whatever that feat is that reduces grit cost).
Trying to balance guns by giving them less attacks than the users BAB would allow per round will only convince people not to use them, since that makes them substantially worse than a bow in most cases. Eventually, mechanics will trump flavor when the players realize how bad it sucks.
I was pretty unhappy with Pathfinder's rules for early firearms, but Paizo recently issued an errata for Ultimate Combat. There were some pretty significant changes for early firearms, so you might want to check it out before making any decisions.
I'll grant that the load times for early firearms in Pathfinder do seem unrealistically fast. Then again, the load times for crossbows seem pretty fast too. I'm guessing this was done to allow these weapons to be useful options in Pathfinder's round based combat where you often need multiple hits to take out an enemy. If a character can't make at least one attack per round that's likely to be frustrating for the player, so I wouldn't advise slowing down reloading too much. If you absolutely can't stand seeing early firearms fired more than once per round you could consider changing the Gunslinger's Dead Shot deed to work more like Mythic Vital Strike. The idea of one slow but deadly shot might fit the theme you're looking for better than than the idea of several less damaging shots. I guess it could also be nice for bypassing DR though there's already a feat for that.
@Claxon - I'm not a big fan of the touch attack mechanic in general though I think that the problem there extends beyond guns.
@Claxon - I'm not a big fan of the touch attack mechanic in general though I think that the problem there extends beyond guns.
Oh it absolutely does, but in general most people targeting touch AC aren't full BAB, they're often full casters with half BAB so it's not as egregious a problem.
@thejeff - Back in 3.5 I made firearms Simple weapons. This seems appropriate to me since one of the advantages of muskets seems to have been that it was easier to train people to use them effectively than it was to train skilled archers. I still think that lowering the rate of fire for PCs to less than once per round would probably create a lack of fun though. There's also the fact that a higher level PC with enough wealth could just go with the "Blackbeard" option and carry multiple loaded pistols for use with Quick Draw, so using load times as the primary balancing factor on firearms could be difficult to pull off well.
@Claxon - I think the touch AC problem has been exacerbated by mid and high BAB classes gaining more access to touch attacks and especially iterative touch attacks. I also think that the OP's problem with firearms might be more thematic than mechanical though.
@thejeff - Back in 3.5 I made firearms Simple weapons. This seems appropriate to me since one of the advantages of muskets seems to have been that it was easier to train people to use them effectively than it was to train skilled archers. I still think that lowering the rate of fire for PCs to less than once per round would probably create a lack of fun though. There's also the fact that a higher level PC with enough wealth could just go with the "Blackbeard" option and carry multiple loaded pistols for use with Quick Draw, so using load times as the primary balancing factor on firearms could be difficult to pull off well.That's pretty much my thought. You could carry multiple pistols, but by the time you can afford that, you're going to be wanting magic ones, which is still going to be hard to afford. Especially if you're trying to lay down the huge rates of fire current pistoleros get.
Less than once per round means you use them at the start of the fight then switch to a melee weapon. You know, like flintlocks were really used.
You just don't play gun specialists.
If using multiple pistols, you could cast Greater Magic Weapon on a bunch of ammo, then you have a bunch of +x pistols.