Home Forums Hunting & Shooting Ask The Gunwriters Seater/Taper Crimp Die?

OK, I've been handloading for years, but this one has me stumped.

I just got a set of RCBS 9mm dies, and it looks like the seater die does double duty as a taper crimp die. The instructions are clear as mud, at least to me.

How can a die seat a bullet and taper crimp without the bullet continuing to move as the crimp is applied, without scraping and deforming the bullet to some extent? I've always done these in separate operations, which seems like the best method, albeit adding an operation to the process.

I'm tempted to just get an additional extra taper crimp die like a Lee. and use the RCBS die as a dedicated seater.

Paul

You can use a standard die for two separate operations. First back the die body out so it won't crimp and then adjust the seating stem to set the bullets where you want them. Then back the seating stem way out so it won't move the bullets and adjust the die body so it crimps the case mouth.

That's my understanding. You can adjust and use the die for one or the other operations, but not both simultaneously.

Another approach I have taken is the use a spacer ring to set the die higher without having to readjust it.

Separate dedicated dies seems like the best approach.

Paul

I always use a separate seater/crimp die for pistol brass. I load all mine on a Dillon 550B and use Dillon dies if available. The few rifles that require a crimp also have separate dies.Rick.

I crushed a bunch of cases before I figured out RCBS didn't mean you to seat and crimp in the same process with their die. Wow! What a revelation that was about 15 years ago! RCBS does not make that clear.

My first of batch pistol ammo was even worse: I though the expander die had to be set so it expanded all the way down to the seating depth of the bullet. I still keep that batch around just to keep me humble. It reminds me to read every instruction sheet thoroughly and cogitate on it for a while before re-reading and actually trying what it says.

As my Dad used to say: "Strong, like Ox. Smart, like Ox." He'd mutter that in German whenever I'd pull something stupid.

OH! One other thing: I'm a big proponent of the Lee Factory Crimp Die. My life improved dramatically when I bought my first one. Even if you don't crimp, it resizes after seating and cleans up a lot of problems.

You can successfully seat and crimp in the same step with taper crimp dies, the trick is all in the setup and not over-crimping. Not having a good picture, a thousand words will have to do.

You start with an expanded mouth, bigger around than the bullet so the bullet starts easily. The seater stem pushes the bullet in and when the bullet is almost fully seated, the very gentle taper of the crimp die begins to move the mouth in toward the bullet – but it only ever squeezes it parallel (mostly) to the bullet, it never turns the case mouth into it. The bullet goes deeper, the mouth moves in toward the bullet until you reach the amount of crimp you want. The mouth has a very tight grip on the bullet for the last few thousandths of seating movement but since it is never turned inward like a roll crimp would do it never actually digs into the bullet.

You can try it with a couple of samples. First screw the die body in but not far enough to start crimping. Then turn in the seater stem to get the bullet seated to the desired OAL. Then back out the seater stem most all the way and begin turning in the die body until it gives you the proper crimp. You can measure the OD of the mouth of a factory loaded cartridge to get a good OD to shoot for. Once you have the die body turned in for the desired crimp, turn the seater stem in again until it contacts the bullet hard.

Then seat and crimp another bullet in one step and measure the OAL. You’ll probably find it a few thousandths longer than the first one you seated/crimped in two steps - if not and it's at the OAL you want then don't worry about this next sentence. If it is a tad long then without touching the die body turn the seater stem in just a bit at a time until this second bullet is the proper OAL. This final seating adjustment may seat a bit hard since the crimp is already applied but don’t worry about that.

Once you have the second bullet at the proper OAL and crimped properly, seat and crimp another bullet in one step. This time the case mouth stops moving at the same time as the bullet stops moving. You can pull the bullet with an inertial puller to verify that the case mouth has not dug into the bullet.

Since a taper crimp doesn’t turn the case mouth inwards like a roll crimp it only squeezes the case wall more and more against the bullet, it doesn't score or scratch the bullet.

I seat and taper crimp all of my 9mm JHP and .45 lead SWC bullets in one step and it works fine.

This is most efficient if you only use one particular bullet. If you work with a lot of different bullet styles it might make sense to seat and crimp in two operations since you wouldn’t have to fuss with the die setup so much every time you changed bullets.

Amen, always one loaded in my progressive - every single round chambers without issue.

I recently started reloading for a couple 9mm pistols.

Ordered the "Hornady Custom Grade New Dimension Nitride 3-Die Set 9mm Luger" and come to find out it does a roll crimp instead of a taper crimp...

WTF?


Ended up buying a Redding taper crimp die.



Was beginning to question the decision to reload for the pistols but was pleasantly surprised to see that my handloads are noticeably more accurate than the factory bought stuff I had been shooting.

Agreed. Lee Factory Crimp dies are a must for my handgun reloaded ammo.

Thanks for the replies, gents.

Very helpful.

Paul