neck expander ball or neck expanding mandrel?

[lpreddick]

after many years of neck sizing only (bumping shoulders with a body die) i am now full length sizing and believe consistent accuracy is improved. with most dies there seems to be a roughness when the expander ball is pulled through the neck...even with redding's carbide button ( i spin a nylon brush in the neck). i understand this might contribute to stretching of the case neck and may require more frequent trimming. i'v tried using a wilson expander mandrel with lube and the expansion of the neck seems smoother. it is early so i can't say if accuracy is better with either. is there a consensus as to whether expander button or expander mandrel gives the best accuracy? the roughness of the expander being pulled through the neck just plain bothers me.

 

[jonbearman]

When I use the carbide ball in reddings etc I always use some sort of neck lube and it glides through with ease and no drag. Using an expander mandrel is really the way to go as it doesn't stress the brass at all and less runout. It just adds one more step to what you are trying to achieve. If you use a bushing die then the expanding is not necessary.

 

[FeMan]

I have found that the expander mandrel gives far less runout than the button. When using a button, I use the carbide one and raise the stem as high up in the die as I can and leave the stem loose so it floats and finds the center on its own. Those steps reduce runout with the button but don't get it as consistently low as the expander mandrel.

 

[fdshuster]

For comparison, look at the difference in the diameter of the expanding mandrel, versus the diameter of the support rod for the expanding button. Big difference. The chance of the mandrel becoming bent is non existant, unless really abused, but if you hit an off-center primer flash hole when de-capping, that very thin rod will be forever bent.

Expanding with a mandrel is the only way to go.

 

[BCoates]

Personally, I have used both methods. I don't turn necks, so I always use and expander of some kind to push the neck thickness variance to the outside. What I have found is, if the expander is doing very little work (sizing up 0.0005-0.001") then the expander in the die works well. If I need to expand up more than 0.001", I use a Sinclair expander mandrel. In both cases, I polish the expander to a mirror finish using very fine sandpaper and/or emery cloth.

 

[amlevin]

If you use a bushing die then the expanding is not necessary.

Provided your case necks remain the same thickness and totally uniform after several firings.

When I use the expander mandrel I find that runout when measured on the outer portion of the bullet is on a regular basis far less than if I merely use a bushing.

Since the cartridge is centered by the shoulder (because I prefer a slight "crush fit") and the bullet is in the lands, I don't really care about a small variation in case neck thickness as long as the ID is true to the case axis.

 

[Barlow]

I have been using K&M expanders in three calibers lately and have to say I'm sold on them. Great people to work with and they know their business. Very uniform neck tension and bullet seating. I'll add more as needed. Barlow

 

[rox]

Best results for me have come from using a Sinclair expander die with floating carbide mandrel. I believe the 21st Century expander with TiN coated mandrels are similar and equally as good.

..

 

[Joe R]

lpreddick said: after many years of neck sizing only (bumping shoulders with a body die) i am now full length sizing and believe consistent accuracy is improved. with most dies there seems to be a roughness when the expander ball is pulled through the neck...even with redding's carbide button ( i spin a nylon brush in the neck). i understand this might contribute to stretching of the case neck and may require more frequent trimming. i'v tried using a wilson expander mandrel with lube and the expansion of the neck seems smoother. it is early so i can't say if accuracy is better with either. is there a consensus as to whether expander button or expander mandrel gives the best accuracy? the roughness of the expander being pulled through the neck just plain bothers me.

lpreddick,
I believe in the age old method of dividing and conquering. Two steps in one seems very attractive until you realize that neither is done very well because of neck wall differences and an expander ball will inevitably pull your case neck a little out of whack. I use a sizing die and a Lyman M expander die to prepare for neck turning. I also use petroleum jelly/sizing wax inside the necks.

If your travelling the road of Long Range Precision, and I believe you are given your question, then you have to cross the Bridge of Neck Turning to continue on your journey. It is a PITA but it's the only way I know to move forward. I know I tried avoiding crossing that bridge.

I remember watching the American Gunsmithing Institute video (AGI 321 - Handloading for the Long Range Shooter) and thinking to myself: "That's crazy stuff, I'll never do that, way too much work." Well after wasting a year and lots of money and effort I finally came to my senses. First I turned necks badly, but after a while I learned to do it properly. After that it's just a matter of finding the right load/velocity and seating depth.

Remember long range matches are like a party, the more the merrier. Hurry up we'll save a spot for you.

Good luck,

Joe

 

[Lapua40X]

... is there a consensus as to whether expander button or expander mandrel gives the best accuracy? ...

I prefer the expander mandrel. But opinions among shooters is rarely the best source of information about which of two options provides the better accuracy. Load ten rounds using each method. Your target will tell you the truth.