Looking for a barrel for a G19 build and came across these. Anybody ever used one? The reviews I can find are good, but there aren't many out there.

I was just looking at those earlier today myself and wondered the same. It looks like the same barrel that Aim Surplus is selling.

https://aimsurplus.com/aimsurplus-glock-19-chf-9mm-ss-barrel-nitride/

TK is the only manufacturer that I have had to return a barrel.  I got a good sale price on one, but it was a complete "jammo-matic."  I tried it in multiple guns with the same results.  I have others, but my go-to is Lone Wolf Distributors.  Not sure what their current availability situation is, seems like everyone has issues with that, but their barrels have proven economical, reliable, and accurate.

Thanks!