Kak upper 300wsm - KAK 22 inch .300 WSM Complete Magnum Upper Receiver

Gun wont work. Jamming issues,accuracy issues couldn't keep a 6 inch group at 100 yards. Gun way over gassed with factory ammo. Bolt not locking closed. Kak doesn't offer for purchase or tell you what buffer weight or buffer spring to have. So I bought a complete stock kit that was useless contacted KAK they said buy a 5.3 ounz buffer. So $70 later that didn't help either so then I bought a $30 heavy spring from springco to help with over gassed that didn't help either. Kak says ready to shoot right out of the box(NOT EVEN CLOSE)! Sending mine back. Buy a Browning BAR they have it figured out!