Mandrel sizing for consistent neck tension

[SealT5]

Just sharing something a friend of mine experienced that is similar to your findings.

When I switched to using expanders on my Redding Big Boss he wanted to try also since I had excellent results. I loaned him my die and Mandrels. He found similar results to you. That he had better concentricity when using a standard Forster die and seater. The only common denominator is that he uses a Coax press and Forster dies. Me I use Forster and Redding dies in a standard O press and seat bullets with an arbor press and wilson dies. I suspect there's something that doesn't jive with the coax and expanders. Rigid vs floating.

There's not right or wrong if the results are achieves.

Joe

I'm fairly new to reloading about a year into reloading and after a month or so of bad ammo that I made I did a bunch of research and bought a lot of tools/items for getting my one rifle I reload for for now to shoot good with low es/sd. So I bought a Sinclair mandrel die, expanding mandrel and turning mandrel, I used this method a lot and thought the runout that I had was basically as good as I could get so I kept using that method. Here recently I decided to try to get more performance and accuracy out of it so I started using better brass and neck turned some to test vs not neck turned. I actually have less runout with the forester fl die without the decapping/sizing stem, necks turned and NOT using the mandrel.....not sure if my mandrel is bad or what, I use imperial dry lube even. Bought the mandrels from PM tool.

 

[Mikecr]

Concentricity is a misnomer for what we need. I could center a banana, making it concentric, but it won't chamber well.
What we need is straight ammo, which measures low in total indicated runout (TIR).
Completely different animals.

 

[IHFarmer07]

Just sharing something a friend of mine experienced that is similar to your findings.

When I switched to using expanders on my Redding Big Boss he wanted to try also since I had excellent results. I loaned him my die and Mandrels. He found similar results to you. That he had better concentricity when using a standard Forster die and seater. The only common denominator is that he uses a Coax press and Forster dies. Me I use Forster and Redding dies in a standard O press and seat bullets with an arbor press and wilson dies. I suspect there's something that doesn't jive with the coax and expanders. Rigid vs floating.

There's not right or wrong if the results are achieves.

Joe

Thanks for that bit of information, thought I was doing something wrong or I have an unfortunate circumstance of a bad part/mandrel or something. That's the thing with reloading and Pete said something similar of this earlier, whatever someone does that works for them in their process may not work for you in your setup. It's just ideas to try and see if it does anything for you, I can't help myself but try some of these new ideas that others have. Reloading is a huge trial and error, much like life!

 

[SealT5]

That's right. I shoot a lot. I shoot well. And I do not own a concentricity gauge. I use what I believe to be the most accurate reloading tools and components. The bullets punch holes where I want them too.

Are my rounds concentric? (Straight) Idk for sure but the targets convinces me yes.

Joe S.