Loosen the front action screw, see if the problem goes away. If it does, then you need to shorten the action screw or install a pillar to keep the screw from jamming into the action.
If that doesn't fix the problem, take out the front scope base screws and see if your bolt goes down freely. If that fixes the problem, then you need to shorten the scope base screws the appropriate amount, then loctite them into place.
Machine guns are awesome until you have to carry one.