Al,

The case neck is anywhere from .001 to .003 smaller on the mouth on the cartridge than on the neck shoulder junction. The reason being that it releives pressure. SAMMI is nervous about lawsuits. When I have a Match grade reamer made it is normally on a straight neck. Which will normally give you higher pressures and more velocity. This is normally what you want, But you must inform the customer that a tight neck coupled with a bullet jammed into the lands can be dangerous. Even on a match grade reamer (one that has a straight neck) may be .001 or so under SAMMI . With the straight neck you also get a better gas seal. This may not be true by turning necks on a factory chamber which has a tapered neck. It may give you something less than a good seal. I might add that the reamer spec. also has a taper unless you specify different.

I see the original 300 WSM has no freebore what so ever and in my opinion.... this is why the boys are having trouble with high pressures.

Stan