He was wrong.
You can shoot .40 in Prodouction, but it scores as minor caliber (like a 9mm) whereas in Limited you get an extra point for peripheral hits (major scoring). In Production everything scores minor, whether it's 9mm or .44 magnum.
Now, if you reload you can downsize the .40 loads and they'll have less recoil than a 9mm. I did some a few years ago that felt like I was shooting an airsoft gun. I've since gone to full SAAMI max on all loads (I now shoot Limited)
Good luck man! I'd have a hard look at the full size guns. They carry just as well and they will do a little better job for ya in matches.