I have two different RCBS seater dies and wanted to know more about one that came with an older die set.  The seater die came with a standard die set labeled Round nose 45 ACP. It has no taper crimp inside.   The bore of the die is straight at the max diameter for a round.  When seating a bullet, the round enters the die and it removes the bell in the case then seats the bullet.  It works just fine for jacketed or plated bullets but sometimes shaves a slight amount of lead if seating lead bullets.  Is this seating die intended for jacketed or plated bullets only?  Does anyone have the RCBS paperwork for this type of seater die?

I have a 25 year old carbide set I bought new, but no instructions for it anymore. It does taper crimp, though. It has the same problem with lead bullets. What I have done in the past is to back off the crimping part and just seat the bullet first, and then set the die back down and crimp in a seperate operation. It has to be cleaned alot because some of the waxy lube always gets shaved off and left in the die. Is it possible that you have a .45 seater die with a roll crimp instead of a taper crimp? The RCBS website lists both kinds of seater dies. If you are loading for a semiauto, you need a taper crimp as the bullet headspaces on the front of the cartridge case. Another  possibility is that you have a seater die from a pistol 4 die set. The seater die has no crimp function like in a pistol three die set, there is a seperate 4th die that has the crimp function. The round nose description just refers to the shape of bullet the nose of the seater matches. Instructions for the use of their dies are on the RCBS website, listed under downloads. Hope something I said helps.

i would call them or check their web site. they are good on supporting their older products and are very helpful.

i worker on their building in Oroville, Ca and got a free rock chucker kit thrown in. good people.

There would be no reason to taper crimp after seating a bullet with this die since as the case first enters the die it sizes it to 0.474.  You can not adjust the seater far enough down to completely seat the bullet before the case enters the die and sizes the expanded case mouth.  All my other die sets, a expanded case can enter the seater die to the taper crimp or roll crimp deep in the die by hand.  I have other old sets of RCBS dies and the directions are the same as the new die sets.  This die must have not been to common, I figured I would get a quick reply from the wealth of knowlege here.

Maybe not a quick reply, but a reply. Your question was kind of nagging me, and I checked my old die set again. Both of the stems on the decapper and bullet seater have the same thread size. I pulled the decapper off the sizing die, and what do you know, the bullet seater screws right in the sizer. Is it possible you have a bullet seater is in a your sizing die? Sure sounds like it from your description of what's happening. The die bodies should be labeled sizer or seater, maybe yours is mislabeled?

This set, the bullet seater is a smaller thread.  The seater die is labeled "seat".  The sizer die has a larger internal thread but since the decapper decaps and flares the case mouth it can not be used with the sizer.  I bought this set used so it may be parts from more than one set.  The sizer and seater die have the same numbers, so I think they are from the same set.

My guess,

You have #3 of a 4 die set.

#3 seats only, by changing the seating stem you can also load SWC's, which you don't have?

#4 die is the crimp die.


What I have done with my RCBS 357 and 45 ACP die sets is buy an extra seating die.

So one seating die always has the RN seater, the other the SWC seater. No changing seaters.

I also added a 4th die to crimp in a separate operation.

So what started as a 3 die carbide set became a 5 die lazy mans (never have to change the seating stem) set.

5 dies just fit in the RCBS box.

My .45 die set is so old, that the seat/crimp die had a roll crimp, like for a revolver.  RCBS did that way back then;  they hadn't gotten used to the idea of a 3 die set with taper crimp.  So I bought a separate #4 taper crimp die, which they did sell.  

The new .45 die sets come with the #3 seater having a taper crimp, not a roll crimp, built in.  Just pull the taper back and seat;  then back up the seater punch and taper crip with the same die.  I think it'd actually be worth the small cost to go ahead and get anothe taper crinp die and make a four die set;  that way you don't have to move things around.

There is no need to use a crimp die after using this seating die since after you remove the round with the seated bullet the expanded neck is crimped already. Please see my previous posts.
I bought this die set so I can have two seater dies set up for RN and SWC. If it was just for seating I would expect it to have a larger inside bore so as to not remove the bell in the case mouth.

What is the ID of the mouth of the die same as mine?

If you just want to seat with this die, run it up a turn or two and lock it down.

Then it will not crimp. Readjust the seating stem.

With any caliber I seat and crimp in seperate dies. YMMV.

No, this will not work.  The ID of the bore of the die is straight, except for the taper at the mouth for the case to start into the die.  As soon as the case has entered the die a 1/8 inch, the expanded case mouth has been sized down; it still needs to go further into the die to completely seat the bullet..  This die is not like a seat/taper die with a neck down almost a case length into the die to remove the expanded case mouth.

OK, you have a die I am not familiar with.