sqlbullet, also when setting the Sizer die, stop short of the shell holder as it can over size and set the shoulder too far back.
Ease the die down in stages of small increments 1/16 of a turn.
Check in the chamber trying for 0.000" (Flush) but no more than 0.002" (below)

I formed a couple pieces last night and thought I would post up my experience as these are different than other case forming processes I have performed.

In the past I have converted 223 to 300 blackout, 308 to 243, 260, 7mm-08, 338, and 358.  Night before last I was playing with a grendel based 358 wildcat and converted some 6.5 grendel to 358.  Suffice it to say I am not really a complete noob at converting one case to another.

But this was my first experience with tiny bottlenecks.

Here is what I did:

1.  I set up the sizing dies as normal, screwed into the press with the ram raised until the die just touched the shell plate.
2.  Prepped a starline 10mm auto brass with a very light rub of Imperial sizing wax
3.  Put the case into the shell holder and raised the ram fully, then retracted
4.  Swapped the sizing die for the seating die cause I am a moron that can't follow directions from Shadow and it looked like the bullet oughtta just seat
5.  Crushed the side of the neck with the bullet, ruining the case
.....
2.  Prepped two starline 10mm auto brass with a very light rub of Imperial sizing wax
3.  Ran the cases through the sizing die without issue

Now I need an expander plug to run into the case neck.  This is the step that traditional bottleneck rifle cartridges handle for you just fine since the expander plug is part of the sizing die.  The 9X25 is too short for a plug to fit properly, and the die set doesn't include an expander die, since Dillon expects you to use a powder drop die for that step.

First I looked to my Hornady American 357/38 dies, but the expander die has a fixed plug that is too short to reach my case.  Next I looked at my Lee 9mm dies, but it is really just a belling plug in the powder thru die, and would not uniform the whole neck.

I have a Lyman M-die for 358 Win and 35 Whelen, but the die body is too long to allow the expander plug to reach.

In the end I took the M-die 358 expander tip, and put it in my Lyman M1 Carbine M-die in place of the .308 expander tip.  This short die body combined with the long expander plug rod allow be to adjust the die so the plug extends out the bottom completely.  This allowed me to uniform the neck all the way.  Unfortunately, the plug is too long for the belling section of the plug to reach the case neck before the nose of the plug hit the bottom of the shell.  But the neck was well uniformed, and since it was a .358" die, belling wasn't really needed.  I could start a .355 bullet with a really hard push of the hand.

So...

3.  Uniform necks with my new Lyman franken die made from two different M-dies
4.  Seat 115 grain FMJ bullets
5.  Crimp and enjoy my two dummy rounds



The extra step with the M-dies should only be needed during the initial forming of the brass, so I will probably form up 500 or so pieces and then not worry about it again.  I also need to get a proper powder die insert and see if it will perform the function of my frankendie.  If it will, then awesome as I can just dump 10mm and 9X25 brass into the hopper for the 1050 and load and everything will come out 9X25.

I have some 115 grain TC FMJ and some 90 grain Gold Dot pulls coming from RMR, should be here on Saturday.  Sunday I will load up some ammo.

Be careful as I understand the Franken die but having the best neck to bullet tension is needed to prevent setback issues.
Also those FMJ's may also pose a setback issue during the feeding cycle as the ogive makes them smaller than 0.3550" for many FMJ types...The straight section of the TC and JHP's can be your best option even if in 0.3560" or 0.3570" jacketed are used.

How was your chamber fit with regards to the flush with the chamber hood of the barrel?  The flusher the better to keep the case necks from stretching forward each shot as that will cause splits and separations as the are used and reused.  They will split eventually anyway.

Take care with the neck expander as that is crucial for bullet retention, the LEE will do the case flare but is short for uniforming the inside all the way down the neck.  I love the RCBS 9mm die for this operation.

The set a bit deep.  I will have to play with the amount of setback on the neck of the die before I make 500.  And I will order a .355" expander plug for the Lyman die too.