Example from BKF: 14.5" with Extended A2 Flash Hider
They sell some uppers and others like it for $400-600 already pinned and welded
>https://bkingsfirearms.com/shop/complete-upper-receivers/bkf-ar15-14-5-5-56-nato-1-7-twist-m4-carbine-4150-cmv-quad-complete-upper-receiver/