The 318 is smaller in diameter, and the same size pawl can get a better purchase on the case than on the 375 H&H. then add the problem prone belt for this type extractor, and you have a problem waiting to happen.

I believe the people who have not had trouble with these rimless extractors, will, generally, fall into a group which have only used the rifles in camparitively clean suroundings, like on a fireing range! The fact that the pawl has to slide between the walls of the opening in the extractor body,must be fairly tight fit to avoid wobbeling. It,also, must work UP, and DOWN,leaving the top open to the dust of Africa, or powder particles, to enter the slot, and bind it up so it doesn't work. I can see no valid reason to take a chance on makeing the most reliable rifle design every made unreliable, by placeing an unreliable feature on it!

Use one of these rifles in wet weather,where a micro-thin layer of rust on the sides of the pawl, and it's receptical, or in dust so fine it make talc look grainy, and the whole thing will change considerable, IMO!

In short, they are an abortion, that does not belong on a double rifle, IMO!