not a good picture, but in side there is an angle cut to start the lug and pull the bolt head onto the case. With out it you would have to slam the bolt hard to get it in far enough to think about closing. the ejector and extractor are going to be fighting against you. also if the case is snug it will fight you. You would not be able to run a slight friction fit. the factory only cuts ramps for the intend direction on travel not both ways. the bolt head lug is kept square to keep its surface area as high as possible.