I'm currently working on a 9mm sbr. My barrel (ADCO) is only 4.5 inches long. I got a great deal on a slick sided vltor mur. Inside the Mur upper will be a CMMG ramped bolt. You can go with a unramped bolt, but then you would need a 9mm hammer in your LPK, as opposed to a normal hammer with the use of a ramped bolt. I know 9mm can be tricky, especially when it comes to getting the weapon to run. I'm not sure about 40 (although I'm sure they would work similarly).
I'm assuming since you're asking about the upper first that you already have a lower? Dedicated 9mm or magwell adapter?
Mark up on this shite is out of hand. And not just Noveske and limited to charging handles. Im talking about accessories not BCG, Barrels, or uppers. I am getting close to calling these makers in the same class as insurance companies.
No I have a Daniel defense ddmv5 lw and a spikes built with a punisher lower in the .223/ 5.56. I'm keeping this one because it's my first ar10. I don't want tons of duplicates (don't have enough room) so if it was a ar15 I'd sell it off. I'd love to go hog hunting with this one...anyone in lafayette need some hog exterminating