Failure to chamber with magazine?

[stokesrj]

I'm thinking you have rounds that are at or near max headspace. The reason they work if fed directly into the chamber is that the higher bolt velocity is able to force the round into the chamber. When fed from a magazine the bolt velocity is slowed down because of the added friction. If you turn your sizing die down another 1/4 turn I bet all will be well.
It is difficult to see just .001 or .002 over spec with a wilson gauge. You almost need a straight edge like a razor blade to feel it.
Take a look and see if that isn't the case.
Bob