Guns can be an important part of a story, but, as a reader, more information about what a gun CAN DO would be lots more helpful than all the specs. I don't know what an AR-15 is, and I'm not going to interrupt an interesting story to go look it up. Even if I did look it up, I probably wouldn't understand it. What would help, would be - "it'll kill a deer from 1,000 yards" or "it's no more dangerous than a BB," or "it blew a hole in him as big as a cannonball." I have absolutely no objection to the specs being in the story - I'm sure they're helpful to those readers who understand them and they may even be impressed by it.. But "it uses a standard NATO round" is of no use to me - I don't know what a standard NATO round is and all it tells me is that the gun uses bullets of some kind. I suspect using that terminology might have been intended to convey to me that the ammunition is widely available, but adding "and you can buy it by the bushel at your neighborhood 7-11" would have not left me guessing. It also doesn't tell me anything about cost. If I wanted to, could I buy a Heckler & Koch MP5K-PDW for the price of a McDonald's quarter-pounder, or does it cost as much as a Fifth Avenue penthouse (not that I know how much that costs, either, but I know it's not cheap). Guns just happened to be the item I used to demonstrate, but it applies to any of the interesting facts in a story. It it takes an expert to understand it - I won't get it.