Does anyone know if a .40 cal upper for an AR is made. My Dept issues us Glock 22's in .40 cal and I was wondering if anyone makes a SMG upper in that caliber. I have seen 9mm and .45 ACP, just never .40 cal. Any and all help is very appreciated.

Olympic makes a .40 S&W Upper.  I considered one for LE use also.  We've been getting a lot of meth labs in the area, and the chemicals make for a volatile environment.  Too much muzzle blast with a short barrelled AR carbine.

Anyhow, I bought one of the Olympic uppers and mag adapters.  The ejector is a piece of bent wire I did not feel comfortable with betting my life on.  The system used a modified UZI mag. The bolt didn't lock open after the last shot.  I like to learn one weapon system and learn it well.  If they made a system with a fixed ejector like Colt or if Colt made a .40 upper, I'd try it again.

Just my $0.03