Used to know a guy who we called "Billy", as in Billy Liar. He would just make stuff up constantly, not necessarily bigging himself up, just random nonsense like he'd just seen the Prime Minister shopping, or he'd bought a Rolls Royce at an auction for only £1000 - we'd say "great, can we see it?", he'd reply stuff like "oh, a guy called at the house last night as he saw it on my drive and offered me £10,000 for it so I sold it". He came up with this sort of stuff daily and everyone called him Billy and some even "hello, here's Billy Liar" to his face and he just laughed it off. In fact, I realize now I never knew his real name! Otherwise he was a nice guy - It's a bit sad really that people can feel they have to do this and it can also get a bit pointless having a conversation with them.
Though in shooting, when you are young, I think it can do harm until you know enough as these guys can make you think you or your gear is not very good since they're apparently shooting stuff way beyond your ability (I remember as a kid that the articles in the air rifle magazines of the 70s and 80s were a bit like that too). It's only as you get experience that you realize what total and utter nonsense they were talking.