If this isn't it, it's damn close:

"Like I said - I smashed a muzzy practice head right through the boiler room on a broadside doe - dead in seconds. Dull broadheads have EVERYTHING to do with KE.

I've killed deer with heads as dull as a butter knife. When I was a kid, I was too broke to afford replacements, so we hunted with 'em until they were destroyed or lost. Good shots always did the job.

Not that scalpel-sharp blades won't help (they will) - but they're just another part of the equation, like everything else.

Pretty simple, really. Run a butterknife over your bare skin at 3 fps. Now run it over your skin at 250 fps. It'll rip right through the skin. It's all about the speed and pressure behind it. If you have energy to burn, a dull blade won't make a lick of difference. "