Some of you guys may remember in the past couple of months that I posted a thread about trying to eliminate leading in my M&P 9mm, using the Lee 124gr .356 TL mold and air cooled WW alloy, with red HF powder coat.
I said I had already ruled out the following things:
-Undersized boolit
-Cases swaging boolit upon seating
-Too much pressure causing gas cutting
-Too little pressure causing failure to obturate
This led me on a wild goose chase where I was making sure my powder coat wasn't over- or under-cured, I wasn't using too fast of a powder (Bullseye vs W231), and I was looking into just buying a different mold (tried some samples of the Lee 105gr .358 SWC for example).
Long story short, I was wrong about being undersized. I was measuring with calipers and they were off. I recently obtained a micrometer and cast 4 boolits from each cavity on my 6-banger mold so I could get an average boolit size for each. Most were dropping right around .355". There's my problem.
So in addition to WEETing the mold (all 6 cavities are now sized to a uniform .359"), I have done some reading on Lee carbide 4-die set dies. I think the reason I wasn't getting bullet swaging when I seated or crimped is because the bullets were roughly the size FMJs or plated bullets anyway. But now I know there are two major dangers for swaging my not-extremely-hard bullets, which I can now confidently say will be .358" after casting, powder coating, and sizing:
1) The neck expander die with the stock 9mm plug in my die set is famously not long enough, so even a stiff case mouth will likely swage the boolit down when I'm seating. I went ahead and ordered the 38 S&W expander plug that I can drop into the die in place of the stock 9mm Luger one, as I found lots of people having success with that method elswhere on the forum. I have also ensured I set my die body up as far as possible in the press so the seating die isn't doing any crimping, and I can save that operation for the next die entirely.
2) The Lee factory crimp die famously contains a ring of carbide that smashes your entire cartridge and whatever is in it (like, say, an oversized cast boolit) down to small enough to always chamber. Guess that explains why I never failed a plunk test, even when using .358 105gr SWCs. I'm looking into three options to ensure this doesn't happen and I can make sure my bullets are actually at .358" when I fire them:
a) Punch out the carbide ring entirely.
b) Grind out the ring using medium grit valve grinding compound on a 9mm casing so that the ring isn't sizing anything down smaller than .361" or .362".
c) Use a different die. I'm looking at 2. This one is a standard non-collet taper die which does not appear to have a factory crimp-style carbide sizing ring. Anyone having success with it? This style looks even better, as I guess collet style dies crimp more consistently regardless of brass length. However, this collet style doesn't come in 9mm. Any chance I could get a 357 Mag die to work as it's roughly the same diameter? Or would the difference in cartridge length between 9mm Luger and 357 Mag make this a no go?
I'd like a collet style most likely unless people are having crazy success with the standard taper crimp 9mm die. Can anyone recommend me one?
Thanks in advance!