'M' dies or custom collet die mandrels?

[JeffinNZ]

Team.

I am loading for .303 Brit and .223 Rem with cast bullets. I was considering 'M' dies from Lyman for case mouth expanding (currently fudging it with other dies) but then thought that as I use Lee collet dies exclusively maybe I should just get Lee's custom dept to make mandrels to suit my neck ID requirements. For the .303 Brit I am mostly shooting .316 these days so the mandrel could be 3145-.3150 and for the .223 Rem with .225 bullets a .224 mandrel. The customs mandrels seem the better option and would save 1) working the case necks more than is needed and 2) one loading operation.

Thoughts?

[dromia]

I still use both.

The Lee Collet dies are one of their best products, still a kit that needs polishing to work as advertised but when you've finished of their product for them it works good.

For up to .315" boolits the standard .303" lee mandrel works well, haven't tried .316".

Wharever you use your still going to have to ease the case mouth for the cast boolits to start, and a suitable "M" die is the busines for that ensuring the boolit sits square to the mouth.

I like nearer 2 thou neck tension.

Anyway for me "M" die or collet isn't and either or option.

[dromia]

BTW if the "M" die speccy is just that 1 - 2 thou different from the mandrel then the "M" die step hardly works the brass.

I've HXP brass that has been reloaded 14 times at circa 2,000 fps velocities and no neck splits yet, suppose I should anneal them.

[HORNET]

Jeff, you should probably measure the mandrels in the dies now before you order new ones. The one in my .223 collet die (and my .222 collet die) was .222 diameter and resulted in very low boolit pull. Springback on the brass was opening it back up to where the expander portion of my M-die was barely touching and, in some cases, not touching at all. I went to polish it down to .221 and overshot (those are real soft) and ended up at .220, which gives just a little more 'feel' on the M-die than I would like but doesn't seem to affect case life and provides good boolit pull. Low case neck tension is a fairly common complaint with the collet dies but it is easy to fix (and cheap and easy to replace mandrels if you oopsie).