Yep, mine are all in and snug. There's a chance they can interfere with the bolt's movement if they are able to go in too far though. If you're up to it, disassemble everything and remove the bolt mechanism, then assemble the upper to the receiver, thread the 4 screws in and feel if they're protruding past the inside of the receiver. You may need to find some washers to shim and keep them away from the moving bits.