Coal, I have BCA uppers in a few varieties in 5.56, 223 Wylde, 350 Legend, and 7.62 X 39. ALL are very accurate.Looking at this. Better price than PSA.
7.62x39 16" Parkerized Heavy|Spiral Flash SCH (bearcreekarsenal.com)
Now, in all AR's of 7.62 x 39 cal there is a possibility of light Primer strikes. Eventually you will see this. The fix is to buy an "Improved" firing pin for this caliber. Or, a heavier hammer spring if you need to.
A lot of foreign made ammo has hard primers. It varies a lot. Russian ammo has been the main problems I ran into.
So I bought an improved firing pin. Problems seemingly gone.
Also, this Belom ammo coming in is good stuff. Brass cases and copper plated fmj bullets. Belom makes Police and Military ammo mostly. A part of PPU in Serbia. Good pricing.