I believe that is what only 5 thousandths per side. 
I have absolutely no knowledge in regards to the Lee Sizing Dies. ?.
But I have also made my own in the past and it was also not that difficult to do.
I myself would tend to think and that is only based on my own past experiences.
If it does not push / creating a fin that is now hanging off of he base of the bullet it should be just fine.

I've reduced .224 jacketed bullets to .221 for a buddy.i had lee make a .221 push die and started first  with a  .223 then .221 and it worked fine.I did lube them .
I also used it to size lubed  .225 cast down to .221 and it worked

JLouis wrote on Jan 12^th, 2023 at 9:53pm:


Ummmm...well..


he's asking about sizing jacketed bullets....

"I would like to size .323 jacketed bullets to .318. "


re- read the post and order a glass stomach !😄😄😄

Don’t know but think I would do in it 2 passes minimum. Lee sizers not real expensive might as order 2 same time. 1 fails you have a wait & additional shipping to get the 2nd

Lees push through sizers are simple and work well on cast bullets. Jacketed will require more press pressure. Some loading presses would be stressed, less in stress multiple passes Imperial die wax will make it easier.  I switch to Arbor press for jobs like you plan. Don’t have a heavy “C” loading press do have 2 Arbors.

Boats

I have an old Rock Chucker I bought in the early 70s, it should with stand the pressure required.
Mike

A fella could make his own with a chunk of 7/8-14 all-thread. Chucking reamers are cheap (around $30 from McMaster-Carr, maybe/probably cheaper elsewhere but they offer them in miniscule increments and you'll have it a day or two after ordering), and diameters can be played with while determining how many (if any) intermediate sizing steps are needed and how much (if any) springback occurs. Afterwards the "final" dies can be heat treated (if a heat treat-able steel is initially selected) if desired. Perhaps if no huge quantities of bullets is forecast a simple low-carbon piece of all-thread left unhardened would suffice - I routinely follow that shortcut when I do this trick for cast bullets only, and they last and last even though unhardened.

I create a tapered entry passage into the die through the simple expedient of a Morse taper reamer gently applied and then polished.

Pushers are equally simple: make it a slip fit in the die and turn the end to fit into the shell holder of your choice. (I use a .45-70 shell holder for all my pushers simply for uniformity.) I'll confess to making most of them out of brass too, for ease in turning. They work fine.

The resulting homemade push-through die can be then used in a reloading press, and is equally at home in an arbor press if extra ooomph is needed.