I have a few feed issues to deal with with the magazines as they don't like to feed properly when loaded above 25 rounds or so, but overall the new upper works just fine.
Isn’t she cute?
standard AR parts except for an AK-74 bbl custom fit onto a standard AR bbl extension. Other necessary mods were sleeves to make up the difference in OD of the AK bbl to the standard AR front sight and some work on the bolt face to allow the 5.45x39 rounds to seat properly.
AR bolt - $35 AK bbl - $90 Bbl ext - $15 Gas tube - $10 Handguards - $18 Various pins - $5 Total = $173