Have you used the gun he is talking about? Given the right conditions (no wind) its not impossible, its is a hell of a shot but its not impossible.
Do you play paintball?
Let me explain a few of the factors for you.
1) Paintballs are made out of a shell filled with liquid paint, the shell is made in 2 halves, it has a seam. Because of this seam even the best paintballs will curve somewhat after they loose so much velocity, it has nothing to do with wind. At 50yds you'd be hard pressed to shoot a grouping tighter then 6 feet, and that is with the best marker, best barrel, compressed air, and best paint. And a Tipmann is FAR from the best marker, in my experience they chop paint like mad, and he was likely using CO2, which causes velocity dips and spikes wrecking havoc with the accuracy.
2) Paintball markers are not used in games at speeds greater then 300fps for safety reasons. 50yds is 150'. 150/300 is half a second flight time. Except it's not really, the ball leaves the barrel at 300fps, but paintballs are big .68 inches to be exact, and they slow down quickly, by 50yds I'd bet they've slowed down by at least 30% (which means you'd get lots of bounces too). Plus that pesky thing called gravity means at that distance you will be lobbing the paint in there with quite a curve, so the parabola actually makes the flight longer. So at 150' the flight time will be close to an entire second, maybe longer, and the balls will be moving quite slowly.
3) The point of the game of paintball is to NOT get hit, therefore the target will either be 90% concealed (just the head sticking out) or moving very quickly. Paintballs are also easily spotted when they are coming at you, or whizzing by. At that range a first shot hit is impossible, even at 30' a first shot hit is tough, it usually takes a few balls to "walk the rope" into the target. The other player will see or hear the first couple whizz by, and will with such slow projectiles at that distance will have plenty of time to react.
4) Those Flatline barrels claim to increase accuracy (not range, only speed can do that) by spinning the paintball. Makes sense people say, after all a rifle is more accurate then a smooth bore firearm. Except with paintballs it doesn't work that way, remember they are filled with liquid paint, so no matter how hard you try to spin then, it just doesn't do much. For an example take a raw egg out and try to spin it on the counter, then try a hard boiled egg, you'll see what I mean. Over the years I've used dozens of different paintball bolts and barrels, some that claim to "spin" the ball, some barrels that are even rifled. I can tell you from experience the best paintball barrels are tapered smoothbore with a muzzle break, anything longer then 14" is pointless too. Basically all those Flatline barrel claims are just marketing BS, and I think some buyers delude themselves into believing it so they won't have buyers remorse. They may be more accurate then the stock barrel, but nearly any aftermarket barrel is.
To summarize, he claims to repeatedly hit a target no bigger then a human head, or moving at full sprint, with a projectile that takes a full second to get there, with accuracy at best in the 6' range, but probably less. I could believe that it happened once, maybe a lucky once in a lifetime shot, but to suggest the he can "pick people off" from 50yds at will, nope... ... paintball markers just do not have the range, sorry.
I still say
BS
