I mean, sure, if that's what you want to do, but that is explicitly not what I want to do here. i want it to feel modern (for varying definitions of modern) and modern means guns.
Most of D&D is actually set in the 19th century just without guns - clothing, cities, ships, professions, governments, legal frameworks, social dynamics, understanding of natural rights, currency, etc - all has more to do with the 19th century than it does with the 13th century. The 19th century is really modern.
Your thread really doesn't surprise me. I've long held the opinion that people can't really imagine anything more than about 150 years into the past, which moves the most distant era people can imagine to like the 1870s and the literature of that period. So I'm not surprised that we're seeing more and more movies to take fantasy out of the 19th century where it has been for a while and move it into the 20th century. It's certainly happening with fantasy books and literature being written today, where more and more of the setting is the 1920s or 1930s just without guns. And so it's not really surprising that we'd also see more and more people going, "Why not just have guns as well?"
And I don't really think guns are a big problem in and of themselves. You can have them in D&D and as long as you confine them to like 18th century firearms, they don't impact play very much or not in the way you'd think. The real impact of guns is it makes a 1st level fighter some degree more of a threat to a 10th level fighter than he would otherwise be. The dynamics don't change very much otherwise. A team of 1st level fighters with late 20th century firearms can take on D&D 10th level characters on equal terms provided they aren't surprised, and are generally a lot more threatening. But that's only a small problem.
The bigger problem isn't guns but stable explosives and artillery. The existence of guns implies those two things, and that really causes a problem. It's a problem if the NPCs start using them, but it's even a bigger problem once the PC's realize "Dynamite!". Most modern setting heroic literature works very heavily on narrative protection and power of plot. Think how the Bond villains never just shoot Bond, or how in Dr. Who they largely do not deal with anything like realistic weaponry. Even traditional Westerns heavily depend on plot protection. Or just think about the incoherence of simulating the comic books in a game where you have to ignore the comic books own lore to get it to work. Everyone just gets protected by the author. That's what you have to figure out how to replicate to go modern, and really I think small arms like say pistols are a small matter compared to the real problems you'll have.
