Have 2, 10.5 uppers (5.56&300blkout). The decision was made because of the interchangeable BCGs. Am currently trying to decide if I need a third in 7.62x39. All psa of course. This ammo sortage/price hike, has got my mind reeling. If you do decide on the 7.62x39 be sure to get an enhanced firing pin and mags to fit. I’ve heard you can use 5.56 mags, just can’t put as many rnds in them.