Bottom Line Up Front: 9mm AR moves more than 5.56 ARs, made me not like the 9mm pistol configuration.
Long rambling explanation below:
Recoil has multiple components. There is the muzzle rise AKA muzzle flip. There is the rearwards force. There is also the intensity or how drawn out that recoil is. Some guns are a push and some are snappy.
For example, some say that .40 S&W has less recoil than .45 ACP, but .40 is snappier due to the recoil being in a shorter time which can make it harder to control.
The Colt pattern 9mm AR15s are blow back operated. Because of this they have heavier bolts and buffers giving them a good bit more mass moving during the recoil of the firearm.
So these blow back 9mm AR15s (well this does apply to all blow back guns) have a more violent recoil then the rarer pistol caliber carbines that are not blow back.
Note that I said “more violent”, not just more or bad. These 9mm ARs are still pleasant to shoot, especially due to the greatly decreased muzzle blast.
So where am I going with this? When I finally got out and shot this 9mm AR pistol I found it moved a good bit with each shot. Shooting accurately was easy. But shooting fast wasn’t.
I was surprised at how well I shot the pistol off hand. Using the iron sights and also an Aimpoint, I was easily shooting tight groups, nearly cloverleafs at 5-20 yards. In hindsight I really should have kept that target. But the gun moved so much off target with each shot I was really off-put by the whole experience.
Now if I had a pistol brace it would probably be a whole different story.
Anyways. I decided I am going to sell this 10.5 inch 9mm upper, and just replace it with a full 9mm rifle. Maybe a Colt 6951. And I have already swapped the pistol over into a 5.56 configuration.