Reloading question. Switching to bushing dies.

[Blackhawk]

I would recommend running an mandrel in the neck to make perfectly round and set your neck tension initially. I do not use bushing dies, however, I remove the stem and set neck tension with mandrels.

I wholeheartedly agree, a mandrel die will expand the case necks I.D. either +.001 or -.001 depending on the mandrel.
As an added bonus you can restore the case necks o. d. if you drop or dent a shell case.(range brass is notorious for this
( I ordered from Sinclair vis Brownell's)
You must order the mandrel die body as well as the correct mandrel when you place the order.
(Note mandrels themselves are caliber specific)
I purchased this initially for neck turning case necks without having them hang up on Neck turning tool's arbor but since have found additional uses for this set.
Hope this helps!

 

[Varmint Hunter]

Get a lee neck sizing die. It has a mandrel. Or just shoot them. They won't be a great fit in you chamber till fired anyway. I wouldn't over think/complicate things.

This ^^^^^^^^^^^^^^^ is the answer.

 

[nksmfamjp]

Without the Whidden option of an expander mandrel of a variety of sizes, my next choice would be using a K&M custom ground mandrel.

Frankly, I like to set neck tension by under sizing by about 0.001" and then expanding with a mandrel. I like it all in 1 die, but can be done as separate operations. The key is getting the neck tension you want without excessive movement of the fired neck.

The best way is when you can control chamber neck clearance too. My 6mmPPC numbers are 0.269" chamber, 0.2665" loaded round, 0.265" neck bushing....I forget the mandrel diameter.

 

[Mikecr]

You don't have to change bushing or mandrel sizes to adjust neck tension.
Just setup the proper sizing(minimal) and adjust sizing LENGTH.
That is, the length of grip on seated bullet bearing.
After all, this is pressure per area (PSI).

 

[nksmfamjp]

You don't have to change bushing or mandrel sizes to adjust neck tension.
Just setup the proper sizing(minimal) and adjust sizing LENGTH.
That is, the length of grip on seated bullet bearing.
After all, this is pressure per area (PSI).

No disagreement in that your post explains how to fine tune, but you have to get close with the mandrel....or bushing for those that skip the last step.

 

[huntinghuasna]

Your Redding bushing dies should have included a standard and reduced button. Use the standard button for new brass and smaller button on fired brass. The standard buttons are 0.002" to 0.003" smaller than given bullet diameter.

 

[Mikecr]

you have to get close with the mandrel

Yes, Ideally close enough so that bullets are not upsizing with seating.
That's 1/2 to 1thou interference depending on cal & condition of necks.
Then sizing 1/2 of seated bearing length is ~half the tension of sizing full seated bearing length.

 

[nksmfamjp]

Yes, Ideally close enough so that bullets are not upsizing with seating.
That's 1/2 to 1thou interference depending on cal & condition of necks.
Then sizing 1/2 of seated bearing length is ~half the tension of sizing full seated bearing length.

I forgot that you and I are the oddballs around here sizing for less seating interference with the bullet...!