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Expander mandrels and die bodies

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I’m thinking about going to an expander mandrel setup and pulling the expander ball and decapper out of my Forster full length sizing die. I’ve read and listened to info until I’m pretty convinced it’s the right idea. I’m thinking I will go with a mandrel 2 thou under bullet diameter for now and then I can add a different mandrel diameter at a later date if I deem it’s necessary or something I want to mess with. So I’m pretty set in stone on doing exactly what I’ve mentioned. My question for you guys is……..Any of y’all use an expander Mandrel? Who’s die and mandrel do you use? I’m currently considering the die and mandrel from 21st century or the die and mandrel from Cortina. The Cortina die does work the bottom portion of the brass that a regular sizing die doesn’t. I can see pros and cons to that. Anyhow……what kinda input have y’all?
 
I haven't spent too much time on Erik's die, but I have no doubt it's legit and works. 21st Century would be my only other choice if I went the mandrel only set up.

I use the L.E. Wilson Die with Mandrel when I use a mandrel. This is only used though on virgin brass or if my brass that takes a bad fall and buggers the neck/mouth. This mandrel is basically just one size per caliber. You can't custom tailor different neck tension settings with this die though. With ADG, Lapua and Alpha brass, I've gotten lucky on .30 Cal and 6.5, that it ends up giving me .002".

I run the Forster FL Sizing dies with bushings or the Redding Type S FL dies with bushings. I never use the expander balls. I pull them immediately and only use the bushing to set neck tension. This takes a fired case and sizes the neck down just enough to get my desired .002" neck tension. Only sizes the bare min. One work one time.

You would be doing the same with the 21st, but you have to get the neck sized down with your sizing die to expand it back up with the mandrel. I know that sounds complicated. I "think" this works the brass more than using the bushing to do it. I've never seen brass fail or wear out quicker this way v's how I do it and I didn't notice an increase or decrease in accuracy one way over the other. I only went this way as it was cheaper for me and my brain said the brass gets worked less.

Just keep in mind: Mandrel's as with bushings, any change in brass manufacture, you will need to get a different sized mandrel to get back to your desired neck tension be it .002" or .003 etc.
 
I ordered from 21st century. We will see what happens. I was already producing very concentric ammo as far as my concentricity tool could tell but we will see what we get now. I have no clue if my brain is jacking with me or not but my brain is telling me:

1) don’t push a ball in and pull it back out of the the neck when you can achieve the same result in one smooth action.

2) the interior of the neck is where the bullet seats so it’s important for this area to be as close to perfect as possible.
 
I agree with both statements, but that agreement may not be worth much, I haven't chased "precision reloads" in a long time. I found I was hitting a wall of diminishing returns, where time to build started to way overbalance what I could hold in practicality.
 
I ordered from 21st century. We will see what happens. I was already producing very concentric ammo as far as my concentricity tool could tell but we will see what we get now. I have no clue if my brain is jacking with me or not but my brain is telling me:

1) don’t push a ball in and pull it back out of the the neck when you can achieve the same result in one smooth action.

2) the interior of the neck is where the bullet seats so it’s important for this area to be as close to perfect as possible.
Let me know if concentrity improves. I have been pondering getting the cortina mandrel die. Neck it down with a bushing die and bring it to finale size with a mandrel. But @rockchalk06 has a good point about over working the brass. If you anneal brass you might not get split necks as fast.

as of now my rifles out shot me. So for me to see an improvement world be hard.
 
That’s all Chinese language to me you guys are WAY AHEAD and WAY more knowledgeable than I am I just use hornady full length dies and hope for the best I’m going to keep reading though
 
Let me know if concentrity improves. I have been pondering getting the cortina mandrel die. Neck it down with a bushing die and bring it to finale size with a mandrel. But @rockchalk06 has a good point about over working the brass. If you anneal brass you might not get split necks as fast.

as of now my rifles out shot me. So for me to see an improvement world be hard.
I’m gonna do some measuring after I pull the ball out of my die and see how much it’s moving the neck.
 
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