I observed a guy complaining about a 30 round mag he had bought there in the store -- the springs were too stiff, he said. Now, I live in a state where any mag with a capacity greater than 10 rounds is illegal unless it was made/brought into the state before 1998...Which means availability is spotty and infrequent. The employee told him they didn't have any 30 round mags in stock, and offered to either take it as a return for a full refund or swap it for three 10 round mags. The guy's response was, "Well, nah...I just want to trade it for a 30 round mag with less stiff springs...So what are you going to do for me?"
I swear, he said that exact statement 3 or 4 times. As a total impartial observer it was slightly maddening to watch.
Don't be that guy.