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Neck expander die ?

Who's neck expander die and mandrel do you guys recommend ?
I will be using them for .308 Win. and 6mm Rem.
I'm trying to get consistent neck tension and concentricity.
Thanks in advance for your advice. Mike
 
I'd use a standard full length sizing die without the expander ball and its neck honed out about .002" less than loaded round neck diameter.

Case necks are usually straighter and better aligned to shoulder axis. Such dies keep case body, shoulder and neck axes in perfect alignment as the case gets sized down a little bit. That ends up with bullets better centered in the chamber at the origin of the rifling (throat) when fired. Case shoulder is then perfectly centered in chamber shoulder; bullets are therefore well centered in the throat.
 
Save yourself the trouble and stick with a good bushing die setup. I've tried the mandrel approach with both .308 and .223 and it wasn't one whit better than a bushing die. The neck tension was no more "consistent", nor was concentricity "improved" (actually, concentricity was fine to begin with). After a few brass preps via the mandrel method, I have gone back to my standard bushing die approach. Why do the extra work with every case if it's not an improvement? If you really want to improve neck tension, turn your case necks.

Like you, I had thought it might be a modest improvement with respect to neck tension, straightness, and concentricity. It wasn't. If you decide to try it anyhow, the good news is that the mandrels and dies are relatively inexpensive in the grand scheme of things. I used Sinclair's Gen II die with their carbide neck turning mandrels, which are held to much tighter tolerances (.0020" under bullet diameter) than the steel mandrels. Just be aware that when opening necks with a mandrel, springback works in the opposite direction than that obtained sizing them from the outside with a bushing die. A mandrel that is .002" under bullet diamteter will not leave you with .002" neck tension (interference fit); more like .0025" to .003".
 
Who's neck expander die and mandrel do you guys recommend ?
I will be using them for .308 Win. and 6mm Rem.
I'm trying to get consistent neck tension and concentricity.
Thanks in advance for your advice. Mike

what kind of accuracy are you looking for?

steps like fine tuning neck tension with expander mandrels are usually used by those looking to improve consistency and group size in rifles that are already consistent quarter MOA rifles.

i use the K&M kit
https://kmshooting.com/custom-diameter-expand-mandrel-kit-for-bullet-tension-main.html

and a 21st century hydro press

but only for.benchrest guns
 
Probably a k&m would work. I had a custom mandrel made for the sinclair mandrel die body. I am choosing a mandrel that is .002 under bullet diameter. This provides .004 neck tension as measured by the inner diameter.
 
Here is another one. They make the most precise die you will find anywhere. The mandrel is held by a heavy duty collet which keeps it perfectly straight so you don't have the run-out that you will hear others complain about with the cheaper commercially available dies. They are a little pricey but it is worth every penny. I think the die body is around $80.00 and the mandrels were somewhere in the neighborhood of $10.00 each. Hope this helps.


Porter’s Precision Products, LLC is located in Lake Jackson, Texas.

Contact Us

Call: (979) 798-9422
 
Who's neck expander die and mandrel do you guys recommend ?
I will be using them for .308 Win. and 6mm Rem.
I'm trying to get consistent neck tension and concentricity.
Thanks in advance for your advice. Mike
Holland Shooters supply has a special going on ,three mandrels for $20 .
 

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