I have on occassion shot in HighPower matches, but I'm not a regular competitor.
Recently I was shooting at a local range, at 200 yard, 10" steel gongs and nailing them nearly every time, shooting from sitting, prone and offhand with a shorty AR carbine and surplus SA ammo. I was hitting everything and having a great day, and a lot of fun.
The only other shooter was a HighPower competitor (who by the way, WAS NOT consistently hitting steel unless he was on the bench).
A third shooter arrived and asked for a cease fire to go down range and put up paper targets at the 100 yard line. As soon as the range is clear Mr HighPower says in a loud voice so the down range plinker can hear, "This is BULLSHIT! This range is for serious shooters..." Then walks over to me, looks at my Bushmaster Shorty and says, "Not a real service rifle", picks up a brown box of my South African surplus, looks at it like its a fresh moist turd in his hand, pronounces one word, "crap", turns around, packs up his gear and leaves, with a considerable fan fare of noise and slamming so we mere mortals could know that he didn't appreciate sharing "his" range with us mere paying club members.
Most of the Highpower shooters are super knowledgeable, friendly guys, and the best shooters around, but AT LEAST 10% (probably more) are like the guy I described.
And the funny part was... the guy couldn't even shoot that good.