I liked the entire idea of a 9mm AR carbine and built one a couple years ago. I was hoping it would be a good range gun and useful for hog hunting. Also a good HD platform
Well....when I got into it, I am sorry to say that IMHO, it fell down on all points. Especially for the cost.
Accuracy was only so so. JP site reports 3MOA, the TAB authors reports 2MOA, neither of which excite me at the range.
Looking at the ballistics of a 9mm round out of a 16 inch barrel....better than a handgun, but marginal for hunting IMHO (though many have reported using 9mm carbines for hunting).
The gun I built was heavier than the usual AR. It had a heavy magwell adapter and heavier barrel. So, it really was not all that great for HD. If I am going to use a 9mm for HD, I might as well reach for my SIG 226....it is just as effective at SD/HD distances.
And the expense. Whew.
SO....it turned out to be an expensive range plinker. FUN...no question about it...very fun to shoot 9mm in an AR platform...but you are really paying for that. Looking at the JP site, even if you just buy the upper and use your lower, you still need the magwell adapter and buffer. So, the cost is $1000.
I quickly sold it and got a 357 magnum lever gun much cheaper, and later a 30-30. Someone has already posted that there are dedicated pistol cal carbine designs for significantly less $.
Not to disparage this, or start a food fight. Just wanted to throw in some opinion from someone who had one. Exciting at first blush...but the infatuation fades quickly.
Hope this helps