Core 15 = crap.

[BPTactical]

The only way things ever get better with QC issues is if folks contact the factory and hold them accountable.
That being said I have built 2 rifles using Core15 components. One used a Daniels Defense complete upper and required reaming the takedown pin holes and some file work on the mag catch opening.
The other the trigger/hammer pin holes were out of spec and the LPK was missing the hammer and detents for the takedown pins.
Not impressed at all

[sniper7]

I'd give it to me. You Dont want that junk

[Bailey Guns]

Let's say you had a transaction with a fellow member here and you sold him/her an item with some sort of issue that (unknown to you) made the item unusable but was easily correctable. Would you prefer the buyer contact you so you had the opportunity to remedy the issue? Or would you prefer the buyer go on to the forum and give you negative feedback without giving you the opportunity to correct the issue.

I'd send it back. You can mail it right to them and have it sent right back to you (unless they replace the bad lower with a new one). You get what you want and they get the opportunity to correct a problem.