This is my Lyman M die.
I love this die. It expands the case mouth and inside sizes the neck after I undersize the neck with a neck sizer with no expander ball. Really irons out the neck nicely and makes he prettiest flare at the top that flat back bullets just sit on the case. The problem is that it is a universal die, and is not self centering for 223 (I use it for 223 on my progressive). If the case does not align perfectly on the expander WHAM!!! Bunged neck opening!!!
The ID is .577″ and the OD of .223 is .375″. So I super glued in a series of O-rings that I glued to together over a bolt. Now it works kind of like a spark plug socket!!! Self aligning!!! No more dinged necks!!!
Note the stack of O-rings. I used thin super glue to secure them to each other and then to the die. Worked very well. Super glue works very well on Buna O-rings.
Here is the die with the case inserted. You can see now, the case is self aligning!!! Finally!! I have ruined a lot of cases with this die (but I use them for 300 Blackout so I don’t get in a twist).