Having been complimented on my apparent knowledge of firearms and explosive devices (all gleefully faked with the aid of a little research) has made me think about the topic of how we acquire apparent authenticity. In my case, all of my facts were picked up through judicious reading plus a half-hour discussion with my brother-in-law, who is a genuine gun-nut. (The only thing I wanted to know was how far a 30.06 could be shot with accuracy given a good sniper scope, but he was so enthused it was hard to keep him on-topic.)
A next-door neighbor in my youth was a member of the Minutemen and the John Birch Society, and I've met other gun-toting right-wingers over the years. I've known a gun-toting left-wing lawyer. I've known more than a few criminal types. And I've known a whole slew of military and ex-military people.
The odd thing is, I think it's often easier for an outsider to write convincingly about technical matters. We are more likely to have an eye for the telling detail. We are less likely to take a reader's knowledge for granted. We are less likely to bury the reader under a dumpload of facts.
I think that what makes technical details work is how the POV character thinks about them, their emotional relationship with the technology. For example, I've never yet written a scene where a doctor uses a scalpel, but it's pretty easy for me to imagine that my fictitious doctor might have strong feelings about (probably against) disposable-blade scalpels, believing that they are less stable and reliable than solid scalpels. I imagine I'll toss in something about "drop-forged steel" (it says that on one of my wrenches) to make it sound as though I know what I'm talking about.
Often I swipe the attitudes and concerns of characters from listening to artists talk about brushes, or to guitarists talk about their instruments and strings...or even from our interminable writer-talk about pen versus pencil versus typewriter versus computer. Though the emotional relationship of human to object is often considered to be "a guy thing," just get a good cook of either gender going on the topic of kitchen hardware. It's not a guy thing, it's a craft thing, and craftspeople of all types share deep commonalities.
Nor is personal experience necessarily a prerequisite for authenticity--at least not in any direct way. As Flannery O'Connor said, anyone who survived childhood has enough experience for a lifetime of writing. It's true. What child hasn't experienced love, grief, fear, anger, delight, frustration? The only thing missing is lust, and that comes along soon enough.
Stephen Crane's The Red Badge of Courage was widely acknowledged by US Civil War veterans as the most authentic description of what it felt like to be in combat. Although Crane was praised by men who had actually fought at the Battle of Chancellorsville, that battle took place eight years before Crane was born, and more than thirty years before he wrote the novel. What is more, Crane had never been in combat, and never served in the military.
The bestselling military writer of our own times is Tom Clancy. Like Crane, Clancy has never been in combat and has never served in the military. From his writerly addiction to military hardware, many assume that he had some inside track, perhaps as a Pentagon consultant. Nope. He was an English major (because he couldn't pass physics courses), and before selling The Hunt for Red October he made his living as an insurance agent. (Since Red October became a bestseller, Clancy has had special access to all manner of technical information through the good offices of many military admirers; but although there is a greater wealth of tech-geek material loaded into his later books, none of those books live up to the shorter, more human, and less-authenticated Hunt for Red October.)
To draw on examples from MNW: Roger Morris is young enough that I'm pretty darn certain he never visited St. Petersburg in the 19th century. Matt Curran may have had demons assault him for all I know, but I'm reasonably sure they didn't do so shortly after the Battle of Waterloo. I know for a fact that Aliya Whitely has never been to Allcombe, because Allcombe doesn't exist. (I asked.) And Michael Stephen Fuchs hasn't had running gunfights with cyber-oriented existentialist gangs--hmm. I could be wrong about Michael. From what I hear, he does have a real-life thing for guns, and computers, and philosophy.
But for most of us, I think, the joy of fiction is pouring ourselves into someone who isn't shaped like us. I'm not a serial killer, but if I were, here's the kind of serial killer I'd be. I'm not an unemployed single mother, but if I were, here's the kind of unemployed single mother I'd be. I'm not a werewolf, but...
Well, okay. I'll 'fess up: I am a werewolf. But I don't write about it.