Strategies on obtaining the Dizzy Yet achievement

Scrakes are the enemies that chase you around with a chainsaw.

I haven't had a chance to play Killing Floor yet since the update, but if it's anything like the Christmas update, Circus Scrakes have replaced regular Scrakes in every level.

According to the KF Wiki:

For the Summer Sideshow he was reskinned into "the Incredible man monkey", a giant cymbal monkey, this time retaining the chainsaw arm.

I believe they start appearing in the fifth wave during a Long game, third during a Medium game.

The Crossbow is sold by the in-game vendor for £800.

The ambassador does 102 damage with a crit (headshot only). If you shoot and don't wait for the target receptacle to shrink back down your next shot won't crit, even if it hits in the head. So in short, you can't kill a sniper in one hit with a headshot unless he has 102 health or less.

So if you want your achievement you have to pick on snipers with low health, shoot from a far distance where they won't see/look for you (like behind them) or soften them up with a body shot, wait for the target receptacle to shrink back down to normal and headshot them that way. The third option is the hardest because a good sniper when shot once will generally move and look around.

My suggestion, go cloak and dagger and get behind their lines. Find a sniper off on his own and shoot him in the head from a far distance. There is no damage drop off over distance for crits (like a headshot with the ambassador). A second option is to find the hurt snipers and shoot them that way.

For a good read: http://tf2wiki.net/wiki/Ambassador

Long range ambassador headshot: