Expander Mandrel Advice

CalCoyote

CalCoyote

Member
I like to go to the range and refine my reloads, but the ammo that I reload is designed for hunting type applications.

I am planning on removing the expander ball from the sizing die on a couple of the calibers I reload for and change over to using an expander mandrel.

Questions: I want the neck tension to be tight enough so that the recoil of the rifle will not affect the seating depth of cartridges in the the magazine.
Is .001 under caliber enough or do I need .002?
What are most factory expander balls machined to?

I tried measuring a few of the expander balls with my calipers on a few full length sizing dies that I have but it was difficult because they most all of them have a taper.
 
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Couple thoughts....

Depending on dimensions, it's possible to induce concentricity issues to the equation when using a mandrel.

Lighter neck tension does not always equal better accuracy.

I always taper & polish the top portion of the expander balls for a smoother transition into the case necks when sizing with expander balls in place.

I also dip the necks in a tub of #9 shot with moly powder prior to sizing.

I would consider annealing as well if you aren't already.
 
Sinclair mandrels are either expanding or neck turning. I use the T turning mandrel. However trim pilots(at least mine) do not work with it, I need to use the expander mandrel, which is slightly larger(about 0.001). Fortunately minimal body/shoulder sizing and no decapper/expander equals minimal case lengthening. You also can polish and turn your expander button to the desired neck I.D. Using my caliper the T22 mandrel is 0.221-0.2215. The E22 mandrel is 0.2225-0.223. You also can get gage pins in desired size and use them in a collet bullet puller(just holds the pin). Gage pins are a cheap way to test neck interference accuracy.
 
Lyman makes a Type "M" die which does the expanding. I would think that sizing without the expander ball on and the just running the expander ball in would be much like expanding with a mandril. Most of the problems with the expander ball is dragging it back through a DRY neck. You can always turn an expander ball to the size you want.

The lee collet die I've had to turn the mandrel down to get proper neck tension.

I do lube the inside of necks before sizing, I have the next size nylon bore brush that I put a little sizing wax on and brush the inside of the necks.
 
The only problem with reducing or removing the expander is that most times, it creats a R.O problem if your using just standard dies. This is magnified when using a flat base bullet. The traditional way to fix the problem is to choose a bullet with a cannelure & just crimp.
 
Run out can occur at several stages, actual firing(chamber not concentric to the bore). Press ram travel in relation to the die. Die body itself. Improperly prepared case necks when seating bullets(especially flat base bullets). Neck sizing bushing die(body of case is not supported and or bushing is not perfect). And other causes. A chamber concentric to the bore will result in a bullet starting down the barrel straight.
 

Increased neck tension is what the O.P was interested in! but all things considered R.O is hard enough to control without using a bullet for a mandrel.
 

And another factoid......bullet diameters between lot numbers can vary over a thou as well.
 


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