no personal experience, but I've heard via members here that at least the barrels with the false suppressor (which I don't think they offer any longer) grouped very well..haven't heard any reports good or bad about the other barrels...at least not that I can remember
but I am on their notify list for when the 18.5" QPQ black nitride barrels are back in stock..
https://www.tacticalinc.com/catalog/product/08324
been wanting to build a truck gun out of one of the black laminate mannlichers I have, and think this barrel, and a Bugbuster, will be a good choice for it