Re: Loading a 40 grain in an AR?
So whats the question? The weight will work fine, usually the 40's are more for the varmint rifles with 12 or 14 twist rates. Sierra rates the lighter .22 cal blitz's up to 4400fps so you wont have to worry about pushing them to hard. Keep an eye on your overall length since its a shorter projectile, on a side note I shoot these on in my 22 250 and they are quite accurate.
CFE is a great powder and meters VERY well. I use it with 55gr varmint nightmares (27.3grs). Just an FYI those can be picked up for less than 50 per 500.
Good luck and happy hunting (paper or whatever)