Why? I guess you could counter with "Why not?" but it doesn't really address the question.

I am genuinely interested as to what functional purpose a 9mm AR would serve. Or for that matter any pistol caliber. There is always the 'cool factor' and 'the look what I got (that you don't got),' But those reasons still don't tell us why?

Weigh in.

because ballistics of handgun rounds out of carbine length uppers are much better than those ballistics of the same round out of a pistol barrel.

its like combining a handgun with a longer barrel, higher magazine capacity and they are generally easier to handle and shoot than pistols.



I want a 9mm AR but it would be more for cheep training than for defense. If I even really needed to use my AR in a defensive scene, I would grab the real thing.

I always asked the same thing as I have owned most every 5.56 upper you can imagine from the 7.5, 10.5, 11.5, 14.5, 16, 20, and 26-inch barrel lengths used with both Pre & Postban AR-15s and an M-16.

With that said, a few months back I decided to take the plunge and give the 9mm uppers a try.  I was quite happy to discover that the 9mm upper I bought functions great, produces a mild recoil and report, and is cheaper to shoot.  Now that I have tried it, I really like the 9mm upper and it has found a perminant place in my collection and some of teh really big advantages include the fact that pistol cartridges are allowed at most every indoor range while 223s are not necessarily allowed.

Now, I will also be honest that I bought this 9mm upper after I bought a Full Auto UZI and SWD M11/9 and I just wanted to add the 9mm upper to the AR-15 so I can consider a 9mm silencer for all three weapon systems.

cheap mags (oly system w socom block), cheap ammo (brass cased for .10/round), quieter, less recoil.  Main reason I want one is the cheap ammo that I can blast all day without shelling out $$$ and deafening myself.....

Because there are no local rifle ranges open in the winter around here, but plenty of indoor pistol ranges that are open year round!