Not to be a dick but that's not true, I can tell you already. 300+ feet shots come from an assload of time, money, and build technique, they don't just happen off a regular old springer.
I've got 2 rifles with more than $500 in each that hardly pass 250 feet. Unless you've got video evidence, I'm gonna have to claim that you're exaggerating.
If you'd like to be a sniper, go for it, but be prepared for lots of time, research, and money going into the affair, which is similar in many ways to the gameplay of a sniper itself.
I cannot prove it, but I am assuming based on many, many reviews I've read of the UTG MK96 stock and long distance shots that seemed to be at least 250-275 feet. It's apparently the best and cheapest mid-level sniper on the market right now. I am indeed prepared to put money into it... as I said somewhere above I already have a line of upgrades ready, I just need to order them when I feel that I need to.
Anyway, I'm really not trying to compete with a bunch of AEGs or cheaters or anything. Like I said, we don't have airsoft arenas or teams up here and we normally just do skirmishes with up to 6 people in woodland areas. They're perfect for the role I'm trying to play.