Do a Google search on Blackthorne Products (aka AR/AK parts kits), marketer of AR parts kits and complete AR uppers, and you'll find lots of negative feedback. Apparently quality control is not one of their strong points. However, recently I caught Blackthorne Products in an out and out lie.
On their website, you will find the following statement:
Blackthorne Products sells only the highest quality parts. We do NOT sell "seconds" of any type, Never have, never will.
That is a lie.
A buddy of mine recently purchased a Blackthorne flattop 20" upper. He wanted to mount a scope on it and asked me to replace the tall A2 sight tower with a low profile gas block.
After removing the sight tower, we made a sad discovery. The barrel on this upper was most definitely not a "first".
Exhibit A: Behold the "D" roll mark, indicating the manufacturer to be DPMS.
Exhibit B: Near the gas hole we find a sight tower taper pin cut, off-center. On the topside of a barrel? Also, ahead of the gas hole we see what appears to be the remnants of another welded over and ground down taper pin cut. How interesting? Wonder what we'll see on the underside of the barrel. A welded over gas hole perhaps?
Exhibit C: Indeed. A welded over gas hole. Off-center near the new taper pin cuts.
But let's not forget. They never sell seconds. Never have, never will. Um ... except for this one time.