.311 x .307 LN Exp. Plug case expander

Did you happen to read the descriptions listed on each page of the those two particular rifle expanders…

I tend to believe that at least one of those two NOE descriptions may just answer your question…

.311 x .307 Exp. Plug
To use with Lee Universal Neck Expanding Die
Turns it in to a true neck expander like a Lyman M-die.
Use a expander that is .001″ over your bullet size for best fit.

The Lyman M die referenced is basically utilized for expanding & belling the cartridge case for cast bullets.  Said Lyman product is basically setup for either a long version, or a separate short version of a particular caliber. The long version would basically be for a specific listed set of cartridges, while the short version would be for a different set of shorter cartridge case lengths. Thus to cover the whole spectrum of that caliber one must buy the long and short versions of that caliber … to be fully covered.

The NOE version by its design will tend to be able to work for both cartridge case lengths Short 0-1.5″ or Long 1.5-3″ at a fraction of the cost of one of those two Lyman… M dies… depending on how one sets up the product.

Another place that one might tend to look to an NOE administrator for an answer to your abbreviation question in regard to LN is:

https://noebulletmolds.com/smf/index.php?topic=2338.0

Unfortunately LN is not on that particular official NOE abbreviation listing and would most probably have to be addressed by the NOE administrator cornmastah… for a more specific & official NOE answer for your particular question…

Your call on getting the LN question listed added to on that forum page string…

Take Care & Stay Safe…