Expanding mandrels..... neccessary?

[Skidly_50]

i have to use my sizing mandrel before i can neck turn and use my 3 way trimmer, then my s bushing neck sizer

I'm now considering putting my expander ball back in my die, you guys are confusing me now

 

[Alibiiv]

i have to use my sizing mandrel before i can neck turn and use my 3 way trimmer, then my s bushing neck sizer

I'm now considering putting my expander ball back in my die, you guys are confusing me now

"IF" you are going to use a mandrel die to size your necks (inside diameter) you have to take the expander ball out of the full-length resizing die, and then resize the neck by running it through the mandrel die to expand the inside of the neck so the neck-turning-mandrel will fit inside of the neck for turning. We are talking about two different mandrels one to resize the inside of the case neck after it has been run through the full-length resizing die and then there's the mandrel on the neck-turning tool. I hope this makes some sense?

 

[338 dude]

i have to use my sizing mandrel before i can neck turn and use my 3 way trimmer, then my s bushing neck sizer

I'm now considering putting my expander ball back in my die, you guys are confusing me now

Mandrel good expanding ball bad

 

[jreagle]

FWIW, at this end of the woods, it looks like when the inside of the neck is not lubricated generously, the expander ball friction causes more run out as it is forcefully pulled out of the neck of the case on the press ram downstroke (handle upstroke). generous lube inside the neck applied with a q-tip and the expander pulls through easily (its really noticeable). Then wipe out necks with a dry q-tip to remove excess lube. Also, leaving the lock ring loose on the FL die expander/primer punch spindle allows a little wiggle room for it to self center when pulling down on the press. Press stroke is important, continuous, even pressure on the handle, down and up, seems to help.
finding that using a mandrel or lubing the inside of the neck with an expander ball results in similar runout, .001 or less.
The forster expander ball and redding carbide expander ball are both giving pretty good results here so far.

Its almost 70 here in CT this morning. Where is winter?

 

[340PR]

I am currently testing how the expansion mandrel can affect accuracy. What I have found so far, is that a good olé Lee collet die will give the most repeatability, not considering shoulder bump. It consistently produces less than .0005" runout (basically, a needle flick on my Sinclair run-out gauge). I bought a set of LE Wilson expander mandrels for both my 6mm, and 6.5mm Creedmoor cartridges.
I was part of a team invited to do testing for a New Zealand company (Annealing Made Perfect). During the process, we found some inconsistencies in our loading process, which made us seriously question what we were doing. A few of us added mandrel expansion to our process, but did not see an accuracy increase in doing so. In fact, we noted an increase in ES, from an average of 6 fps, to 14 fps. One of our shooters recorded 4" groups @ 1000yd with a 6mm BRA, another recorded sub 5.5" groups, with a stock Tikka in 6.5CM.
That said, I hope to have more data in the next few weeks on how "exactly" mandrel expansion affects accuracy.