D&D 5E What I've learned running Modern/Sci-Fi Games with D&D 5E

[Ruin Explorer]

You can stab someone more than once every six seconds too. If it's bothersome, just say that a combat round represents 3 seconds instead of 6.

You know perfectly well that melee combat isn't "stabbing someone". Shooting at people is distinctly different to engaging in melee. People know this because they've done it - even have done just paintball and fencing shows the distinct differences.

3 seconds doesn't square up well with other stuff, like movement. So adjust movement distances, eh? And then we can see a chain-reaction of various changes and basically we're playing a different system.

A better solution, I suggest, would be to default to having multiple attacks with ranged weapons on all classes. Advantage/Disadvantage works well with this (taking a single attack could give Advantage, two or three could be the default, and you could take an extra X over the default but all attacks would be at disadvantage). Alternatively damage could be factored assuming multiple attacks (just unspecified), and you could not track ammo instead (instead have a roll-range which means "out of ammo" perhaps - then you need to use an Action to reload if you want to fire that gun more).

Unfortunately these are not options systems I've seen have actually used. Instead you typically just see large amounts of damage and single attacks, but still tracking ammo precisely.

 

[Enevhar Aldarion]

However you make the system, it better be able to recreate John McClane from the Die Hard movies. With everything he goes through and is still able to function and make perfect shots, even with all the HP damage he takes, he would be at least a mid-level modern version of a Fighter, or maybe a multi-class even.

 

[Flamestrike]

SWSE simply gave 1st level PCs [Max HP x 3] at 1st level.

If I was running a Sci Fi game I'd simply give PCs 1st, 2nd and 3rd level Hit dice (and HP) at 1st level (and then nothing at 2nd and 3rd).

Fighters have 30 HP (plus Con x 3) at levels 1, 2 and 3. Wizards have 18 HP (plus Con x 3) at levels 1, 2 and 3. And so forth.

No multiclassing until you've hit 3rd level either.

Then you can toss out 3d6 and 3d8 guns whever you want them.

 

[Urriak Uruk]

There's certainly plenty of sci-fi based 5E games out there.

To be clear, my post is not intended to say that 5E can't work better for sci-fi with modifications. It's just meant to point out that the barrier to run your own game of modern/sci-fi is much lower than one would first assume, and is very doable with just owning a copy of the DMG.

The big issue I find with modern stuff and weapons is the six-second combat round vs. the fact that you can fire off entire clips in that time, yet only get one attack. This often makes thing seem utterly ludicrous. Even with some aiming, taking cover and so on (especially as that is also often not happening), it's just not plausible.

Spycraft really fell apart in part because of this. The idea that you can only fire a pistol once in that time just doesn't work, and it doesn't work with "you can fire more but you'll miss lol" because I'm sorry, but we all know that's not how it works. Especially at very very short range (like 10' away).

Whereas in D&D, if anything, the fire-rates of ranged weapons tend to be slightly optimistic (in some cases wildly optimistic).

With sci-fi lasers etc. this is less of an issue, because it's easier to handwave it as peculiarities with the weapons themselves. Just don't mix in conventional slugthrowers or questions will be asked.

Hit points also sometimes need a bit of a rethink. Basically I would say the sweet spot for D&D is clearly solidly prehistoric to early-mid 1800s, but it also works fairly well at extremely far-out sci-fi. It just doesn't work well at modern-day stuff, particularly, because of the peculiarities of modern-day combat.

Perfectly fair complaint. I've never worried about it too much, mostly because I've always found the "six-seconds" per round of combat fairly unrealistic in all situations (fights that take two hours of real-time take one minute of gameplay?) Also, you get multiple attacks as you level, so you can fire off more bullets if your a better sharpsooter.