Super fun little 9mm. I have several 9mm ARs, largely due to my shooting club having numerous Pistol Only ranges than allow use of pistol caliber carbines, but not "rifle" cartridges on the 50 yard ranges.
If you don't have experience with the blowback AR 9mm platform, you'll learn the recoil is similar to the .223/5.56. I can tell the difference in the recoil pulse/duration, but effectively the 9mm recoil mass is similar to the rifle cartridge recoil without the gas cycling dwell time. In other words, recoil feels real similar.
Since you mentioned it… The 9mm also picks up some slight velocity boost in the 16" barrel over most shorter pistol barrels (peak velocity is 14" or so barrel depending on loading). That velocity bump and the weight/shape of a pistol bullet means the 9mm may have similar/greater penetration than a .223 inside 50-100 yards.
This penetration used to be a contentious issue in U.S. law enforcement, as some LE administrators would restrict AR rifle purchases to 9mm only. The agency shooting instructors would occasionally "forget" to mention the 9mm was a better penetrating round in plate glass, sheet metal and wall board than the .223/5.56. Aging results in memory lapses, right?
Smarter folks than I can lecture on the ballistic performance elements, etc. The 9mm is not going to be a realistic 800m cartridge like a .223/5.56, but I absolutely can ring steel plates at 150+ yards with a 9mm pistol caliber carbine.
