http://www.law-guns.com/ar-15300blackout8pistolbarrel.aspx

Just curious if anyone has used one of these barrels? ive read a few reviews and they seem legit. i called the company and the exact length is 8.2 1:7 twist. The guy i spoke with said a few of the people who work there run them at are grouping 2.5" at 200 yards.

I have the bull barrel version of it, I have not shot it much yet and only at short range, so I can't say anything first hand about the long range accuracy.
I do like it, fit and finish are fine, mine has a great polished bore.
I do know one of the people that posted a review on the law guns website about the exact barrel that you linked to, he is very happy with it & I trust that he knows his stuff, that is why I bought mine, I just liked the heaver barrel, the only difference.
That's all I have, since nobody has replied I thought would throw it out there, when the weather gets better and I can get to longer range I'll update this post.

awesome, thanks for the reply cant wait to see your results.