FL sizing w/mandrel

BuckRub · June 18, 2014, 05:50 PM

Let me get this straight. Ive read on here that some recommend sizing brass but with no mandrel - (i think thats correct).
Anyway I set up a die to push shoulder back to about .002 back on bolt guns and .004 on autos. I use Full length RCBS dies but with mandrel just like it comes and have not had a problem with accuracy. What benefits not using a mandrel ? could someone who does this please explain why and how and why its more accurate. ? Do you just leave the mandrel out of the sizing process ?

Brian Pfleuger · June 18, 2014, 07:17 PM

Most dies over size the neck and the expander ball on the decapping pin stretches it back out to an appropriate size. Doing so can also pull the neck out of alignment with the rest of the case and works the brass more than necessary.

Depending on how small your die sizes the neck without the expander, you might be able to seat a bullet and let it do the job of the expander. This is not ideal, the bullet is not designed as a neck expander.

Better solution is to use dies with interchangeable bushings to size the neck, that don't require an expander or Lee Collet neck dies. Bushing dies size from the outside and so require reasonably uniform outside neck diameters. Lee Collet dies press the neck against a mandrel on the inside and so outside neck diameter is irrelevant.

Bart B. · June 20, 2014, 10:12 AM

I've known a couple of people who resized fired .308 Win. cases in full length dies with the decapping rod removed. No expander ball at all so the sized case necks were quite small.

Seated bullets had a lot of jacket material scraped off; unbalanced them.

When fired with normal maximum powder charges, the pressure was way too high. Well flattened primers. Accuracy was horrible.

If you don't want to use an expander ball (a great idea for best accuracy and long case life), have your die's neck honed out to a diameter about .002" smaller than a loaded round's neck diameter. Or get an RCBS or Redding full bushing die with a bushing diameter .002" smaller than a loaded round's neck. Maybe a .003" smaller one, too.

Here's a link to Redding's site; check out their full bushing die's:

http://www.redding-reloading.com/onl...s-bushing-dies

chiefr · June 20, 2014, 10:53 AM

I have removed the expander when I have had to resize pre primed brass that was not the preferred dimensions.
I have also removed expander when reloading obsolete and rare cartridges with oddball bullet diameters.

Removing the expander is not something I do in day to day reloading, but if you can seat bullet w/o peeling the jackets or falling into the case, press on.

June 18, 2014, 05:50 PM	#1
BuckRub Junior member Join Date: October 3, 2012 Location: Central Texas Posts: 1,046	FL sizing w/mandrel Let me get this straight. Ive read on here that some recommend sizing brass but with no mandrel - (i think thats correct). Anyway I set up a die to push shoulder back to about .002 back on bolt guns and .004 on autos. I use Full length RCBS dies but with mandrel just like it comes and have not had a problem with accuracy. What benefits not using a mandrel ? could someone who does this please explain why and how and why its more accurate. ? Do you just leave the mandrel out of the sizing process ?

June 18, 2014, 07:17 PM	#2
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,694	Most dies over size the neck and the expander ball on the decapping pin stretches it back out to an appropriate size. Doing so can also pull the neck out of alignment with the rest of the case and works the brass more than necessary. Depending on how small your die sizes the neck without the expander, you might be able to seat a bullet and let it do the job of the expander. This is not ideal, the bullet is not designed as a neck expander. Better solution is to use dies with interchangeable bushings to size the neck, that don't require an expander or Lee Collet neck dies. Bushing dies size from the outside and so require reasonably uniform outside neck diameters. Lee Collet dies press the neck against a mandrel on the inside and so outside neck diameter is irrelevant. __________________ https://ecommercearms.com I am the owner/operator! Ask me for custom prices! No sales tax outside CO!

June 20, 2014, 10:12 AM	#3
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	I've known a couple of people who resized fired .308 Win. cases in full length dies with the decapping rod removed. No expander ball at all so the sized case necks were quite small. Seated bullets had a lot of jacket material scraped off; unbalanced them. When fired with normal maximum powder charges, the pressure was way too high. Well flattened primers. Accuracy was horrible. If you don't want to use an expander ball (a great idea for best accuracy and long case life), have your die's neck honed out to a diameter about .002" smaller than a loaded round's neck diameter. Or get an RCBS or Redding full bushing die with a bushing diameter .002" smaller than a loaded round's neck. Maybe a .003" smaller one, too. Here's a link to Redding's site; check out their full bushing die's: http://www.redding-reloading.com/onl...s-bushing-dies

June 20, 2014, 10:53 AM	#4
chiefr Senior Member Join Date: January 27, 2010 Location: AR Posts: 1,401	I have removed the expander when I have had to resize pre primed brass that was not the preferred dimensions. I have also removed expander when reloading obsolete and rare cartridges with oddball bullet diameters. Removing the expander is not something I do in day to day reloading, but if you can seat bullet w/o peeling the jackets or falling into the case, press on.