You can, of course, wing it when it comes to descriptive writing. In fantasy and science-fiction that purely imaginative approach is unavoidable. No one has actually seen a dragon, for example, or a slime monster from Alpha Ceti. But if you are attempting to achieve a certain realism, it helps to have some experience with the subject matter you are describing.
Action scenes often involve gunfire. It can be readily apparent from certain scenes in novels when writers have zero experience with firearms. Though, admittedly, readers with the same lack of experience probably notice nothing amiss. This is one area, at least, in which I can avoid some common pitfalls.
Experience, of course, can dim. So why not brush up from time to time? I went with MBW and some friends to a gun club. MBW was eager to break in a new purchase. I was eager to refresh the scents, the sounds, and the feel of hurling lead down range and hoping it hits somewhere near where I intend. Since I have a major action scene coming up in my work in progress (a sequel to a series which I will discuss in more depth next week) the timing was fortuitous.
After shooting, lunch and libations are crucial. To this, we added axe throwing. Now, how am I going to work that experience in? Perhaps something with the Franks in the Dark Ages. Hmmm.