Answer: That depends, do you have one of THESE???
TH over at homebrewtalk created a pneumatic bottle capper which we think must be made of pure awesomeness.
Here's what he had to say about it:
"The air cylinder is a 2" bore spring-return cylinder with a 5/8-18 threaded rod end, which is perfect because a standard capper bell screwed right on. On the base I stuck on an "alignment" plate that I made out of lexan to make it easy to align the bottles each time. By the way I only use one size of bottle so I built the capper accordingly. Obviously it wouldn't work for very many other sizes. In the video its running at 100 psi."