Quote Originally Posted by 1eyedog View Post
Gotta move with the times . Champing at the bit is grammatically correct, but dead in the English language. Chomping at the bit is 20 times more known and popular and hence is now the accepted (unofficial) form. Chomping is also a variant of champing and is alive and well inn the English language. Champing as I said is now obsolete.
Chomping doesn't actually make sense though:

YOU’RE SAYING IT WRONG! CHAMPING VS. CHOMPING
In the end, it’s just wrong to say “chomping,” because “chomping” is a transitive verb, or a verb that needs an object for it to make sense. In other words, you have to have something to chomp on if you want to use “chomp.” A horse doesn’t chomp, or bite, the bit—he champs, or grinds, his teeth. No bit is necessary for a champing to happen, so champing is an intransitive verb, which means no “object” is required.
To be honest the grammar doesn't worry me, it's just the saying is champing, you can't just go and change it! There are heaps of sayings that are outdated but we don't just go and modernise them for the hell of it.