Seat/Crimp Die Adjustment


April 12, 2007, 08:26 PM
:banghead: New kid on the block, here, trying to set up my .40S&W RCBS seat/crimp die for the taper crimp. I read and followed the RCBS instructions. Twice. Massively confused. How can a simple device with very few moving parts be so hard?

Quoting here:

"To adjust the seater die, place a sized, primed and powder-charged case into the shell holder and run it to the top of the press stroke. Screw the taper crimp seater die into the press until you feel it touch the mouth of the case. Back the die up one full turn and set the large lock nut. This will leave a gap between the bottom of the die and the shell holder. Lower the case and insert a bullet into the case mouth. Slowly run the case up into the seater die. Check the bullet for proper seating depth. If the bullet is not seated properly, adjust the seater plug until the proper depth is obtained. Next, adjust the die to crimp. While the uncrimped cartridge is still in the seater die, unscrew the seater plug several turns. Then screw the seater die downward until you feel it touch the mouth of the case. Lower the reloaded cartridge and adjut the seater die down about an 1/8th of a turn. Run the reloaded cartridge back into the seater die and check the crimp."

Mark me confused. After running the case to the full "up" position, and screwing the die body down until I made contact with the case (and even running the seater plug all the way down), the shortest I could get the round, with Hornady XTP bullet, was 1.135". This was no where near the 1.125 called out in the load formula. And what's with this part about backing the die out a full turn? At first, I though that I might have somehow "over-flared" the mouth when expanding the case, so that it touched the sides of the crimp die too early. But that doesn't make sense because I tried this same piece of brass several times in the seater die, which had the effect of straightening out the flare without visibly causing crimping. The closest I got to a crimping effect was to create a very slight interference fit with the bullet, which was easily extracted using a kinetic puller.

Any and all help is appreciated.

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April 12, 2007, 08:52 PM
Read your first line of the instructions again, I do not see where it says to bell or flair the case.

Go thru the instructions with an unbelled case. This will put the die much lower and put you the path to a proper crimp.

April 12, 2007, 08:52 PM
I'm not sure why your particular die isn't seating quite deep enough.

In general, setting the seat/crimp takes several stages when starting with the bullet out of the case.
Step 1. The idea is to get a bullet seated to the correct depth and not crimp the case while doing it. That's why you back the die out a full turn after contact with the case.

Step 2. The idea is to set the crimp without seating the bullet any deeper. So you back the seating stem out enough that only the crimp is being adjusted.

Step 3. Lock the die body in position (it's now set for crimping). Run the round up into the die then turn the seating stem down until it makes firm contact with the bullet. That resets the correct seating depth. Lock the seating stem adjustment (if your dies allow it).

That should get you setup. If your die doesn't allow proper adjustment, I'd call whomever made it for tech help. Reloading companies are generally helpful and will replace defective parts.

April 12, 2007, 09:05 PM
I fully understand the theory of the seat/crimp die, as described by 1911user, but thanks for the confirmation.

This die is part of a three-die set, the second being the expander. The "belling" I was describing was my view of the ever-so-slightly visible expansion of the mouth of the case after it went thru the expander. BTW, I worked at getting only the slightest of expansion to the case so that I wouldn't work harden it, so that's why I don't think I over-did that part.

I'm wondering if perhaps this particular die came with the wrong seater plug (one that is too short). That would explain my inability to push the bullet in far enough. I'll call RCBS tomorrow.

Thanks for the response.

April 12, 2007, 09:19 PM
NavArch; Your very small bell is the correct approach, but it is still an increase in the diameter of the case mouth. When you are dealing with thousanths of inches, any bell is a BIG deal.

I've loaded close to 55-60K 40S&W with lots of different bullets, I know the drill. Try the no bell first.

April 12, 2007, 11:20 PM
the bell will contact the sides of the die too soon and mess with yoiur head.
Don't read things into directions that aren't there.
Not that I would ever do that.:rolleyes:

April 14, 2007, 10:18 AM
Thanks to Shoney for diagnosing my apparent problem. Like Quasimodo, I had a problem with bells. I had been concerned that not having enough expansion would cause interference problems with the bullet. Over-compensation was obviously not the answer.

My no-primer-no-powder dummies now mic the correct length and are 0.422 (corrected number) diameter from extraction groove to mouth. It takes 5-7 whacks with a kinetic puller to remove the bullets. Anything else come to mind before committing myself to producing charged rounds?

April 14, 2007, 11:44 AM
Nav, not sure about how many whacks you should need to pull a bullet but one thing I do ( I use plated bullets which are softer than FMJ) is check the bullet after. IMO you don't want to see dents into the bullet from crimping. Very slight mark only. Sounds like you probably got it right.

April 14, 2007, 11:50 AM
Sounds like you are good to go.
I would suggest that you get a seperate crimp die and do the seating and crimping in two operations.It makes it soo much easier to adjust settings,and limits the amount of shaved lead or jacket material that will end up in the seat/crimp die.

April 14, 2007, 12:25 PM
Bullets retrieved from the puller show slight scuffing only, if any marks at all. No indentations. I have a Lee Factory Crimp die on order so I can separate the seat and crimp functions.

Appreciate all of the suggestions.

April 14, 2007, 01:37 PM
Glad to help. Doing the seating and crimping separately is a good idea. It is most important when loading hard cast lead and plated bullets, because a single operation crimp shaves lead and/or gouges into the bullet. Be sure that you do not over crimp, especially when loading the lead and plated. Apply only enough crimp to hold the bullet to keep it from being set back.

Good shooting!

July 2, 2007, 04:38 PM
Bless the search function - this appears to be the question I was about to ask when my backordered shell holders showed up. The progressives I've used had separate seating and crimp dies.

My new pistol 3-die sets have instructions about the same as the OP and I was having a hard time picturing how one can be inserting a bullet simultaneous with forming a case such that a bullet has trouble moving.

According to the nice folks at Redding, if I'm running a heavy crimp (H110) with JHPs I'm likely better off doing the operations separately as would be the case with a cast bullet.

I gather I can either raise the die body and lower the plug to seat the bullet than lower the die and raise the plug to crimp (only) the previously seated bullet. Or just buy a crimp die. The latter option looks like the easiest approach.

So when does one use a seating/crimp die adjusted to do both operations at once? Medium crimp on jacketed / light taper crimp on lead - that sort of thing?

July 2, 2007, 05:32 PM
When using jacketed bullets, applying a taper crimp.

July 2, 2007, 07:04 PM
When using jacketed bullets, applying a taper crimp.

Would that apply to the revolver rounds as well? The combo seating / crimp dies I got are supposed to be roll crimp (I believe Redding calls them "profile" crimp"). The rounds that headspace off the mouth are shipped with taper crimp combo dies.

I can buy separate profile/roll crimp dies or taper crimp dies but it appears if I'm buying combo dies for my revolver rounds I'm stuck with roll crimp.

I did hear that a roll crimp "starts" as a taper crimp. If so, I could just adjust the roll crimp combo die "light" and wind up with a taper crimp - does that sound right?

TIA - FWIW, I'm currently loading .357 Mag, H110 & Hornady XTP 158 grain on an XL650 with separate dies. The XTP has a cannelure if that's at all relevant. I was counseled to give the load a "heavy" crimp and was presuming that meant "roll crimp" and a stout one besides, however, my association of "roll crimp" with "heavy crimp" may not be at all accurate.

July 2, 2007, 10:11 PM
Hawcks question was, "So when does one use a seating/crimp die adjusted to do both operations at once?"

My answer was, "When using jacketed bullets, applying a taper crimp. "

Please explain to me what part of that was unclear.

July 2, 2007, 10:49 PM
My answer was, "When using jacketed bullets, applying a taper crimp. "

Please explain to me what part of that was unclear.

The answer isn't so much unclear as I haven't found a combo die for revolvers that includes a taper crimp - the ones I've found have always been roll crimp.

Hence the follow-up question:
If one puts a "light" adjustment on the roll crimp combo die, does that constitute a sort of taper crimp?


Do I just need to look harder for a revolver combo seating / crimp die that includes a taper crimp?

In other words, when I'm using jacketed bullets in a revolver round, it doesn't appear I have the option of a combo die that offers a taper crimp. So far, the only ones I've looked at only offer a roll crimp. I understand you're telling me to use a taper crimp in a combo die, it's just not immediately apparent where such a beast comes from. I've thus far only checked Dillon and Redding so there may well be another manufacturer offering such a thing.

Alternatively, I could attempt to make the roll crimp behave like a taper crimp but I'm not sure that's possible or if that's what you're suggesting.


Jim Watson
July 2, 2007, 11:18 PM
My answer was, "When using jacketed bullets, applying a taper crimp"
Please explain to me what part of that was unclear..

It isn't unclear, but it isn't right.

Revolver ammunition should be roll crimped if you are using revolver bullets with crimp grooves or cannelures for the purpose. The only place for a taper crimp on a revolver load is for ungrooved cheap plated bullets... which I won't use.

July 2, 2007, 11:20 PM
Hawk, usually jacketed bullets for revolvers come with a cannelure or crimping groove. One can safely and properly roll crimp a revolver case into that crimping groove. Normally, that's just for heavy loads with slow powder. I find a good solid crimp doesn't hurt much of anything.

Taper crimps are appropriate for non-cannelured bullets and pistols that headspace on the case mouth.

I use the Lee Factory Crimp die on about everything I have. And I crimp in a separate step from seating.

Jim Watson
July 2, 2007, 11:28 PM
Oh, yeah, furthermore I consider a seating die that will not admit a case with a reasonable amount of flare on it to be defective. I quit using an RCBS .45 ACP seating die for that reason, it would close the flare and the case mouth would scrape copper or lead off the sides of the bullet. Lyman, Lee, and Dillon don't do that.

A straight pistol case needs some flare to start and seat a bullet without scraping the bearing surface, which cannot be good for accuracy. I think there is too much emphasis on not "overworking" the brass. I will most likely lose an autopistol case before I wear it out anyhow.

July 3, 2007, 11:11 AM
I guess if roll crimp is the generally accepted practice in revolver loads, that would explain why combo seat / taper crimp dies in .357 are relatively rare.

I ordered profile (roll) crimp dies for the 3 die sets I ordered previously (.357, .41 Mag and .45 Colt). The .357s I'm currently loading are with Hornady XTPs which have a cannelure. Evidently, these could use the combo seat/crimp die for both operations simultaneously but it looks like doing these in two steps is the way to go.

And if one is going to two-step it anyway, might as well use a separate die as that would seem to make better use of the Hornady LnL adaptors I was planning on taking for a spin.

On a related note, the Lee factory crimp die seems to have quite a following. Naturally, I start thinking of this after buying the Redding crimp dies but what they hey. Anyhow, I gather the main differences between the Redding and Lee is that the Lee has some voodoo that permits it to not go bugnuts when fed over-length cases and is available in a wide range of rifle rounds. (Redding's rifle crimp dies seem to be limited to rounds associated with semi-autos or tubular magazines).

I should be good with the Reddings for now as I'm only loading .357, .41 and .45 Colt, all with virgin Starline, so I haven't hit any case length issues yet. I don’t load any rifle yet. Would the FCD generally be a better choice than simply going with whoever made the rest of the die set?

Jim Watson
July 3, 2007, 11:24 AM
The purpose of the Lee Carbide Factory Crimp die is to resize the loaded round. This squishes things down so variations in bullet diameter and brass thickness don't give you ammo that won't chamber. Target shooters don't like them because it will distort the bullet and may, although I haven't seen it, loosen the bullet in the case. But if you are loading blasting ammo with mixed brass and bulk bullets, it is good insurance.

The Lee CFC CRIMP is no different from any other; it taper crimps auto calibers, roll crimps for revolvers. So if your die set's seater-crimper or separate crimper give you good ammo, there is no reason to change.

July 4, 2007, 10:57 AM
NavArch it seems you have run into the same problems i did when i started loading the 45 ACP. I use Hornady Titanium Nitride Dies to size , flare, and then seat the bullets on the 3rd die , and set the 3rd die where it brings in the flare some but not crimp it. Then i use the factory crimp die from Lee to crimp the rounds in a separate operation. My overall lenth using FMJ hardball is 1.255 inches. On the crimp area right where the bullet meets the case the reading on a vernier caliper should be .470 inches. This should give you the proper crimp. IN CHECKING MY SETUP I AM ACTUALLY USING THE TAPER CRIMP DIE FROM LEE # 90785, is the Lee number on the instructions. I have no problems using this die for the final crimp. In 7 45 acp pistols they all run without a hiccup. Hope this helps and good shooting.

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