crimp or not to crimp

Rounder · May 28, 2000, 10:34 PM

Hi, In reading a lot of post here I see where some reloaders crimp their reloads for auto loaders. I thought that auto loaders should NOT be crimped since it would put a taper on the mouth which is how headspace is determined. Im concerned with 9mm Parbellum, and 45 ACP. Thanks in advance.
Rounder.

**Bud Helms** · May 28, 2000, 10:53 PM

Rounder,

A properly adjusted taper crimp doesn't crimp the case mouth far enough down to cause that problem. It will bring the mouth of the case back down after belling and makes the mouth perfectly round. Most importantly, it doesn't roll the case mouth into a soft lead bullet or a cannelure. The mouth stays straight (as in an extension of the case wall) and doesn't roll it over and cause bulges. It's the best way to avoid chambering problems caused by crimping.

I experimented once with adjustment on my taper crimp die on .45 ACP rounds with lead bullets and never could get the case mouth down past .469. A lot of variables there, though.

MADISON · May 29, 2000, 01:41 PM

I always thought a TAPER CRIMP DIE was a sizer die with the stem taken out. You use less than 1/3 of the die to bring the bullet and case together.

I have 'real' taper crimp dies for all rifle and handgun calibers.

**Bud Helms** · May 30, 2000, 08:39 PM

I thought a taper crimp die could taper a case too far to get a bullet started in seating. Interesting. I never heard that before. Could it work?

Big Bunny · May 30, 2000, 11:06 PM

Either mild taper-crimp or none atall should be OK, most seater dies will also TC (as well) all in one operation.
To use a FLS die to taper-crimp will need another press operation, but it is possible with care. ( ...but without the decapper stem of course!)

Some accuracy and reliability is claimed for taper-crimping but it depends a lot on the tolerances of your individual pistol/projectiles/cases whether it is worth it. Try 10 or so rounds and then try it on the range.

I leave the mild belling on my own .40S&W cases(6.7gn of W540 with lead 155gn SWC proj ) as they are still a drop-in fit in the chamber (with or without) and the more positive headspace stop /"cleaning action" of the nonTC round may be an advantage if a lot of rounds are fired, but my tests are still continuing on that!

------------------
***Big Bunny***

**Bud Helms** · May 31, 2000, 05:13 AM

'Never hear of a seater die that would taper crimp.

**Mal H** · May 31, 2000, 12:49 PM

Me neither. Think about it. For carbide dies, the carbide portion is short and has a slightly smaller ID than the remainder of the die well. For standard steel dies, the ID is considerably smaller than the ID of the crimp die. I suppose you could use the sizer die as a crimper but it would have to be rigged in a threaded sleeve so it could be raised an inch or so higher than normal - very impractical.

deguello · May 31, 2000, 02:50 PM

sensop, i have a carbide die set and it's stamped right on the seater die "rcbs 45acp taper crimp".
i've just started reloading so there might be a better way, but the ones i did this way seemed to turn out just right.

**Mal H** · May 31, 2000, 03:24 PM

Oops. I read sensops post as "sizer" die based on MADISON's post.

sensop - did you mean seater or sizer? The seater die does do the taper/roll crimping.

Or, did you mean to add a question mark at the end?

[This message has been edited by Mal H (edited May 31, 2000).]

**Bud Helms** · May 31, 2000, 06:55 PM

I did mean the seater die. I was commenting on Big Bunny's post. Now that I've read your second post and Deguello's post on his RCBS dies, I think I learned something. I thought that all the seater dies roll-crimped only. Therefore, I thought a taper crimp had to be a fourth stage for a straight walled case. Apparently not.

That's very interesting. A hole in Sensop's great store of knowledge. I will be damned (for a multitude of reasons, actually). This is very unsettling. I must now go medicate on this. I think a Killian's will do nicely.

[This message has been edited by sensop (edited May 31, 2000).]

Big Bunny · May 31, 2000, 08:09 PM

Sensop...I think it depends upon the degree angle ground on the inner surface of the die by the maker and importantly the calibre it is designed for - IE if it headspaces upon the mouth or the rim.
My LEE 40S&W appears to taper crimp, but my 38SPL crimps hard in a line into the groove (if neccessary).
However,this aside, I would appreciate your (and anyone else's advice) on my topic regarding magazine capacity of a CZ-75 on this page.

BB.

------------------
***Big Bunny***

May 28, 2000, 10:34 PM	#1
Rounder Member Join Date: May 6, 2000 Location: Camden, ME, USA Posts: 16	Hi, In reading a lot of post here I see where some reloaders crimp their reloads for auto loaders. I thought that auto loaders should NOT be crimped since it would put a taper on the mouth which is how headspace is determined. Im concerned with 9mm Parbellum, and 45 ACP. Thanks in advance. Rounder.

May 28, 2000, 10:53 PM	#2
Bud Helms Senior Member Join Date: December 31, 1999 Location: Middle Georgia, USA Posts: 13,198	Rounder, A properly adjusted taper crimp doesn't crimp the case mouth far enough down to cause that problem. It will bring the mouth of the case back down after belling and makes the mouth perfectly round. Most importantly, it doesn't roll the case mouth into a soft lead bullet or a cannelure. The mouth stays straight (as in an extension of the case wall) and doesn't roll it over and cause bulges. It's the best way to avoid chambering problems caused by crimping. I experimented once with adjustment on my taper crimp die on .45 ACP rounds with lead bullets and never could get the case mouth down past .469. A lot of variables there, though.

May 29, 2000, 01:41 PM	#3
MADISON Senior Member Join Date: January 1, 2000 Location: Roanoke, Virginia Posts: 2,678	I always thought a TAPER CRIMP DIE was a sizer die with the stem taken out. You use less than 1/3 of the die to bring the bullet and case together. I have 'real' taper crimp dies for all rifle and handgun calibers.

May 30, 2000, 08:39 PM	#4
Bud Helms Senior Member Join Date: December 31, 1999 Location: Middle Georgia, USA Posts: 13,198	I thought a taper crimp die could taper a case too far to get a bullet started in seating. Interesting. I never heard that before. Could it work?

May 30, 2000, 11:06 PM	#5
Big Bunny Senior Member Join Date: August 9, 1999 Location: New South Wales - Australia Posts: 605	Either mild taper-crimp or none atall should be OK, most seater dies will also TC (as well) all in one operation. To use a FLS die to taper-crimp will need another press operation, but it is possible with care. ( ...but without the decapper stem of course!) Some accuracy and reliability is claimed for taper-crimping but it depends a lot on the tolerances of your individual pistol/projectiles/cases whether it is worth it. Try 10 or so rounds and then try it on the range. I leave the mild belling on my own .40S&W cases(6.7gn of W540 with lead 155gn SWC proj ) as they are still a drop-in fit in the chamber (with or without) and the more positive headspace stop /"cleaning action" of the nonTC round may be an advantage if a lot of rounds are fired, but my tests are still continuing on that! ------------------ *Big Bunny*

May 31, 2000, 05:13 AM	#6
Bud Helms Senior Member Join Date: December 31, 1999 Location: Middle Georgia, USA Posts: 13,198	'Never hear of a seater die that would taper crimp.

May 31, 2000, 12:49 PM	#7
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,949	Me neither. Think about it. For carbide dies, the carbide portion is short and has a slightly smaller ID than the remainder of the die well. For standard steel dies, the ID is considerably smaller than the ID of the crimp die. I suppose you could use the sizer die as a crimper but it would have to be rigged in a threaded sleeve so it could be raised an inch or so higher than normal - very impractical.

May 31, 2000, 02:50 PM	#8
deguello Member Join Date: September 12, 1999 Location: tx, usa Posts: 43	sensop, i have a carbide die set and it's stamped right on the seater die "rcbs 45acp taper crimp". i've just started reloading so there might be a better way, but the ones i did this way seemed to turn out just right.

May 31, 2000, 03:24 PM	#9
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,949	Oops. I read sensops post as "sizer" die based on MADISON's post. sensop - did you mean seater or sizer? The seater die does do the taper/roll crimping. Or, did you mean to add a question mark at the end? [This message has been edited by Mal H (edited May 31, 2000).]

May 31, 2000, 06:55 PM	#10
Bud Helms Senior Member Join Date: December 31, 1999 Location: Middle Georgia, USA Posts: 13,198	I did mean the seater die. I was commenting on Big Bunny's post. Now that I've read your second post and Deguello's post on his RCBS dies, I think I learned something. I thought that all the seater dies roll-crimped only. Therefore, I thought a taper crimp had to be a fourth stage for a straight walled case. Apparently not. That's very interesting. A hole in Sensop's great store of knowledge. I will be damned (for a multitude of reasons, actually). This is very unsettling. I must now go medicate on this. I think a Killian's will do nicely. [This message has been edited by sensop (edited May 31, 2000).]

May 31, 2000, 08:09 PM	#11
Big Bunny Senior Member Join Date: August 9, 1999 Location: New South Wales - Australia Posts: 605	Sensop...I think it depends upon the degree angle ground on the inner surface of the die by the maker and importantly the calibre it is designed for - IE if it headspaces upon the mouth or the rim. My LEE 40S&W appears to taper crimp, but my 38SPL crimps hard in a line into the groove (if neccessary). However,this aside, I would appreciate your (and anyone else's advice) on my topic regarding magazine capacity of a CZ-75 on this page. BB. ------------------ *Big Bunny*