I have a RCBS progressive press that I've been using for many years. I recently got into loading 9mm with it, and am having issues with 115gr RN bullets. I've never loaded RN's before, all FP or HP in several calibers. I have both bullet seating plugs for the 9MM, and use the RN one, of course. But it still seats the occasional bullet cocked in the shell. I've pulled the RN seating die out of the holder, and it does not really match the shape of the bullet very well. I bought some FP bullets and used the other seating die with much less issue. But need to get it working well with RN as that's what the wife prefers to shoot (and I have over 1000 to use sitting on the shelf!).

So my question is, is there a better seating die for those 9mm RN bullets? If not, I might try to talk a machinist buddy into making it a better fit, unless someone thinks that would be a bad move.

I think taking your seating punch to a machinist, along with a couple of the bullets you want it to fit, is a very good move. A quick-and-dirty fix, if you've got a taste for adventure, is to chuck your seater punch in an electric drill motor, clamp a 3/16 (or thereabouts) drill bit horizontally in a solid vise, and rotate the punch against the bit to a depth of 1/8" (or so).
This will relieve nose pressure on the bullet, transferring the bulk of the pressure to the ogive, but depending on how soft your bullets are, may leave a ring-mark on the nose. Maybe have a spare punch on hand, ya know, just in case ?

Larry

RCBS alternate seater plugs for 9mm. Alternate Seater Plugs - 1/2 inch-20 thread - RCBS

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Science plus Art

I'd call RCBS and explain the situation to them. Maybe they now have better dies for your application. It never hurts to ask......

I like the seating die from Hornady. It uses a sliding sleeve that centers the bullet as it seats. The sleeve contacts the ogive & not the point, so straighter seating.

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NRA Cert. Inst. IDPA CSO

That link only lists .40/10mm when I select Round Nose. I already have the RCBS RN seater for the 9mm, but it's odd they don't list it at that link.

I'll give them a call.

Few options...

* Have a machinist fix match it up for you.

* Send a bullet to Lee (I believe Hornady still does it too) to buy
a seating die and have them match the seating stem.

* Use a minimal amount of JB Weld on the business end of the
seating stem to 'custom fit' the actual bullet you have. Hot
glue works too, but never lasts.

* Dremel the seating stem (or a spare stem) to properly fit.

Let's step back a bit and take a look at why the bullet gets cocked in the first place.

I'll be honest here - I load up 2000 rounds at a time on my Dillon 550B, and I may go from
- Hornady gr HAP bullets (a hollow point but with out an grooves in the jacket so it won't expand); to
- a round nosed hard cast lead bullet; to
- a Hornady 124 gr XTPs (hollow points); to
- a 124 gr truncated cone bullet that works well in my Luger and Walther P-38;to
- a 147 gr plated round nose bullet that works great for subsonic loads in my Uzi.

Over the whole 10,000 rounds all I will adjust is the seating depth of the bullet. I don't change from the round to the flat point seating stem and back again. And to be honest I couldn't tell you for sure which one I have in it (although I'm pretty sure it is the round nose stem).

I normally use the round nose stem as a flat stem will put flat noses on thin plated round nose bullets with really soft lead cores.

The point here is that what results in a cocked bullet is more often than not inadequate belling of the case mouth. Yes, you don't want to go crazy with belling as it over works the brass and will shorten case life. But no, you don't want to be so stingy with the case belling that you are shaving lead on a cast bullet, or not enabling a jacketed bullet to start cleanly and evenly.

Try just a smidge more belling of the case and see if that resolves the problem. Then if it's still a problem, worry about the seating stem in the die.

I had what was likely a more minor version of what the OP is having, and I solved it along the lines of what BB57 describes.

In an effort to minimize brass wear I'd really gone to the absolute minimum mouth belling. It was to the point where I could get the bullet aligned/vertical, but it was quite a challenge. I increased the bell just enough so the bullet now drops pretty comfortably into place before it goes into the seating die. I still do have to make sure it is pretty well aligned. But it's a ton easier with the increased bell. My rate of cockeyed bullets has basically gone to 0.

OR