According to this site (http://www.duckpins.com/common/info/specs.html) the pins are set 12 inches apart center to center. The maximum width of a pin is 4.125 inches, so the space between pins is 7.875 inches. The ball is no more than 5 inches in diameter.

That said, it wasn't duckpins I played, it was candlepins.

Edit:

In candlepins (http://www.candlepinbowling.com/Rules.htm) the ball is only 4-1/2 inches in diameter and the pins are 2-15/16 inches and they're *still on 12 inch centers. Note the interesting pin combinations that are named (http://www.candlepinbowling.com/candlepin_language.htm), so presumably relatively common. Particularly see the half Worcester and the full Worcester.