ive managed to get some of my friends to try D&D along with my current players. i thought a one-shot could be a good idea as to give the inexperienced players a fun introduction to D&D without having to commit lots of time. After talking with them all we agreed to a high fantasy wild west heist but i was wondering if the D&D 5e system will work with a more shoot-y setting. i know there is the guns optional rule but will that be enough?

any help is greatly appreciated!

It can work...but I'd have to question whether D&D is the best engine for it. It's highly centered around melee weapons and magic, two things that Wild West games lack. If by fantasy you mean you're including magic, then sure. Personally, I'd reskin the various bows and crossbows as guns to provide variety, and you're golden. I'd also impose disadvantage on melee attacks to encourage the use of guns. Sure, the major pillar of melee will largely be missing, but it's survivable.

Personally, I'd set it in a more traditional fantasy setting to give them a better taste of D&D...but that's your call.

for Western themed games, I actually prefer the Cortex System RPG rules from Margaret-Weiss, that first came out of SerenityRPG.

Eberron's set up to be pretty wild west-esque. You can also treat wands like weapons, especially with ranged spells.

There's no need to impose penalties on melee weapons. If you let your players pick cool guns, they will build around guns for the most part. You might have a contrarian who wants to use a lasso. You should probably figure out what a lasso is gonna do in your game because there's no rules for it and you can bet it's gonna come up.

Quote from pocketmouse >>

Eberron's set up to be pretty wild west-esque. You can also treat wands like weapons, especially with ranged spells.

 i did think about eberron but the problem is though that i dont have the book

The D20 combat system doesn’t really simulate the tension of a Mexican standoff or a gun duel very well, to be frank. 

Quote from TrippyHippyEcho >>

The D20 combat system doesn’t really simulate the tension of a Mexican standoff or a gun duel very well, to be frank. 

 Are there any tabletop game systems that do?

Quote from TrippyHippyEcho >>

The D20 combat system doesn’t really simulate the tension of a Mexican standoff or a gun duel very well, to be frank. 

 It works well enough at low levels. 1-2, maybe 3 if your guns really hit hard. The trick is that you shouldn't rule it as everyone readying actions, because that just leads to a predictable outcome. Instead treat it as an initiative contest the moment someone tries to shoot.

You might try the variant rule where each round, everyone locks in their turn, and then initiative is rolled for the round. I've never tried it but it seems like it would give that sense of quick-draw drama.

Well, the major Western/Fantasy game is still probably Deadlands which uses the Savage Worlds ruleset these days. And, yes, I think it is better suited to Western style duels and shooting combat. The use of cards for initiative could be brought into D&D easily enough, but the wound system is also needed. If you have a typical abstract HP system used in D&, the idea of whittling down an opposition through a series of melee exchanges just doesn’t work. In Savage Worlds, and other systems, if you get shot you take a wound and it has an impact. Lots of other game systems have more immediate and consequential effects of being shot.

Actually, one of the best systems I’ve seen for gun-based combat was the old Games Workshop Judge Dredd system. In this, you had an Initiative score as a percentile and a Strength score of 1-3, which served as a wounds total. Whenever shooting started there was a risk of getting shot which could take a character out immediately (especially if they were just a basic Perp), but otherwise it would whittle away at the Initiative score. The Initiative score didn’t just determine when characters acted but how many times over 12 rounds. These actions could be offensive or defensive (like dodging) but the character’s Initiative score wasn’t fixed and was reduced by near misses or trying to do complex actions. If you whittled away at the Initiative enough, then characters couldn’t act in time to avoid being shot. 

Lethality of combat doesn't automatically equate to making the system good for a Western theme.  Plenty of protagonists in Westerns could walk off being shot, after all.

A number of systems like traveler and Alternity also do a better job of simulating the western including allowing for the actual weapons not reskinned mideveal weapons. Effectively in DND in a western setting you want a martial PC with the ranged fighting style, the alert feat, high Dex, then the fighting initiate feat to take unarmed fighting  or you want the tavern brawler feat. Later you have to have sharp shooter and some way to get advantage on initiative as well. So everyone looks pretty much the same. Most folks will take fighter or Paladin ( do smites work on ranged attacks?) ( tells you how often I play a Paladin) but I prefer the ranger as the nature and survival skills still play in well. The one thing that doesn’t fit in well is that in a gunfight you are often safest holding still. For what ever reason folks assume you will be dodging and shoot for where they think you will be not for where you actually are - the best example of this is the OK Corral gunfight - everyone except Wyatt was moving as well as shooting and everyone else got hit at least once. Wyatt stood stock still firing and while bullets passed close none hit him. He actually did pretty much the same thing again latter when he accidentally surprised the rings kid and a couple of others while stopping to urinate and had to pull up his pants, grab his belts and get back on his horse and go- quickly. Bullet holes in his hat, duster, jacket but none in him. Actual gunfights were and are crazy things. In 1989 guns and ammo magazine took a look at NYC police gunfights - range 2-5’, shots fired: 12, hits: <5 (including grazing hits), “one shot stops”: <25%  both the cops and bad guys were basically playing “quick draw McGraw”. The next year they gave the cops vests and trained them in  “point and shoot”. The results: range stayed the same, shots fired dropped to 8, hits stayed about the same but the number of “one shot stops” zoomed to over 75%. Of course after that everyone went to high capacity semi autos, the bad guys started wearing vests too and the number of innocent bystanders hit skyrocketed and now everyone seems to have moved on to assault rifles with the results we all see

No, 5E is not written for a wild west setting.  you will be doing a lot of work.  You are giving flintlocks and a rifle and that's about it.  There are no Wild West classes by official 5E rules.  You could hit up DM'sguild and most likely find some mods using licensing.  I've only played the two below.

Weird Frontiers compatible with Dungeon Crawl Classics or Deadlands: The Weird West using Savage Worlds rulesets are both made for the Wild West, have a ton of content (modules, monsters, forums) that will make your DM life a lot easier.

If you really don't want to use a new system, you could buy their modules and convert them to 5E to save yourself a fair bit of time as well.  Just understand you'll be doing a lot of a modding and there are already game systems created that would help you with ideas already.  If you want some inspiration read "Seventh Son", its about an alternate US mid 1800's where everyone in the world have a knack and the hero is a seventh son of a seventh son with quite a strong knack.

A number of systems like traveler and Alternity also do a better job of simulating the western including allowing for the actual weapons not reskinned mideveal weapons.

Yep. Traveller is a very good system for running Westerns with. It isn’t just about the lethality of combat. It’s the whole tactical set up of how combat is approached. And, no, it just isn’t something that D&D is well set up for.

If you’re going high fantasy, I bet you could pull it off with just reskinning. Turn bows and crossbows into guns and expect mostly dex builds since most everyone will want to use guns, because Wild West. There could be a problem there, as D&D combat usually involves/assumes some people in melee while others are using ranged weapons, but the Wild West has very little melee. Except for the odd fistfight, but you really don’t see folks with glaives or great axes. Swords, however, could certainly be around. But that’s where the reskinning comes in, it’s just a weirdly big sword and use the greataxe stats.

To me the biggest challenge would be horses. Riding horses is pretty iconic part of the setting. But horses are really very fragile in this edition. You might just treat them all like flavor and say no ones horse can be injured, no matter how many fireballs go off.

Your table will know what’s right for them, but I’d also be careful of importing the racism that comes with that era. For example, don’t make all the Native American tribes barbarians.

Quote from ChoirOfFire >>

You should probably figure out what a lasso is gonna do in your game because there's no rules for it and you can bet it's gonna come up.

 Call it a net.

Problems I can see with using D&D for the system are:

1: Reloading. The whole thing with a lot of gun fights is running out of ammo, and that sort of thing - counting shots. D&D will basically ignore this, as most people would take a feat to ignore the loading property of a gun. Loading itself is not good for representing guns, because you can carry multiple shots in a gun.

2: damage. In the west, getting shot was going to take you out of the fight, dead or not. D&D sees people shrug off hits from a greataxe. 

If I were to try and run a Western game, which I now might because I have been thinking about it, I might make these modifications:

1. Drop Strength. In all likelihood, Strength will not come up in a Western game. Instead, replace Strength with "Reflex", which will replace Dex for initiative rolls. The reason for this is that Dex is used to aim a gun, and if you also use Dex to determine how fast you do so, then Dex becomes king of the game - anyone not maxing it will suffer.
2. Loading becomes an action. How many shots you can reload into a gun is based on your Sleight of Hand skill.

Now, problem there is that the game now relies on guns and magic, and all melee players are off the table. Strength is gone as an irrelevance. Barbarian is useless as a build, and the game basically needs rewriting.

I made a game once - never got to play it - which was this style: Wild West, played in 3.5, with guns but otherwise a fantasy setting. 

Since I didn't want a gunslinger game (if I did, I'd have picked another system, almost certainly Deadlands), I made special rules for guns. Basically, culturally, guns were reserved for duels, and using them in a wider combat setting was considered irredeemably low, cowardly and villainous, because it was impersonal, random, if you missed you might kill another target, a bystander or even a friend. 

So ... guns = duels. 

And that was basically: If you win initiative, you fire first. If your attack hits, it's Save or Die. On a save, you'd still roll damage, measured not against HP but against Toughness score, so you might die anyways. 

Like I said, never got to play it - in the end, I played Deadlands instead - but the principle stands. Maybe I should give it a shot =)

I played in a wild west 3.5e hack using guns, for over a year. We had a Sorcerer because the player just wanted to play one, a Cleric because someone wanted to be a dwarven prospector, a Rogue variant snake oil salesman, a Druid because it's the strongest class, and a Monk/Ranger multiclass playing on American Indian tropes. The Rogue died and I brought in a Fighter using a spiked chain and calling it a lasso.

I also played in a one shot with Savage Worlds, where we had a barbarian crazed war veteran, a mad scientist bomb guy, and I don't remember what else.

Believe it or not, players value self-expression. You're not going to get five identical gunslingers.

Quote from ThorukDuckSlayer >>

2: damage. In the west, getting shot was going to take you out of the fight, dead or not. D&D sees people shrug off hits from a greataxe. 

 This one is not an issue. Hit points are an abstraction and do not equal physical damage. They can be glancing blows, hits that might hurt without killing you, twisting out of the way, and general fatigue and a bit of luck. They don’t mean you took the brunt of an axe blow 10 times. They mean you managed to avoid it 9 times before number 10 actually hit you. There’s no reason that system can’t work with guns. 

Quote from ThorukDuckSlayer >>

Problems I can see with using D&D for the system are:

1: Reloading. The whole thing with a lot of gun fights is running out of ammo, and that sort of thing - counting shots. D&D will basically ignore this, as most people would take a feat to ignore the loading property of a gun. Loading itself is not good for representing guns, because you can carry multiple shots in a gun.

In a proper Western, you only run out of ammo when it would be dramatic.  Otherwise, you only shot five bullets.