So I've decided to build up a .40 AR. I'm loathe to add a new calibre to our extant group so .223 is right out. I've seen that the .40 is a relatively new 'thing' in the AR world but I've got my heart set on one so that the fam can become familiar with the rifle. It helps that I can load a few thousands rounds a week to blast away with. So I'm looking for any members who have their AR chambered in any form of pistol calibre to give me the pros and cons of this type of configuration. I've never actually laid a finger on an AR but have read a fair bit on their form and function.