My 404 sizing die set is an original Lyman which I bought back in the late seventies through my local gunshop. The old Mauser bore showed a bit of wear so I got the die made in .425". It came in the proper Lyman die tube stamped .425". They must have offered a custom service in those days, perhaps still do if asked. Von Gruff and I have exchanged bullet moulds and cast bullets which we size in our dies and then shoot wonderfully in our 404s.

My 400gr mould casts plain base and I have never got great results with these bullets until turning a shoulder and crimping gas checks on, then they really shoot. Without the gas check I noticed some lead splashing back onto the necks of my cases so am assuming there is some gas cutting of the plain base. My 404 has been very long throated probably for the early monometal bullets of the day.