Mandrel/Arbor for .334 bushing

[Flogain]

My loads measure .3375 ID loaded round. I tested with a 21st century mandrel, but it makes the ID about .336 to 337. I first used a .335 bushing. This is supposedly .0025” tension, but with spring back I’ll assume it’s 2k tension. Well, I want to get a .334 for 3k tension because the rounds move up a tad in the violent chambering of the SCAR 17. If I want to ID bushing size to .334 (my thinking again is that with spring back, 3.5k tension becomes 3k) to possibly reduce rounds moving forward in the chamber (only about 2-4k maybe I should leave it?) which mandrel/arbor should I use to push inconsistencies back to the outside, and not change the ID I just created? I know this maybe sounds dumb, but I bought the .30 cal mandrel from 21st, and obviously wasn’t thinking. I don’t like to roll like that. I’ll need a mandrel that is like 2k less than .334 right?

My process for brass (both new and fired I think since I want to do the same for all) would be mandrel in the mouth first, bushing the ID, and then here I don’t know. I know I want to get rid of inside inconsistencies. I think that is a smart move. So maybe I should get a .332 bushing and a .334 mandrel? Please help, gents and ladies.

 

[918v]

I think you have all of this screwed up in your head. First, tell us what brass you’re using because neck wall thickness is important.

 

[Flogain]

IMI match brass. Neck thickness is about .016-.018” with calipers. I don’t have a micrometer at the moment.

 

[918v]

OK, do your loaded round OD Is .3375”, and you wanna use a .334” bushing for .003” neck tension.

Your mandrel needs to be .305”, so get a neck turning mandrel, not a neck sizing mandrel. A neck turning mandrel is smaller in diameter. They are not exactly .305”, but plus minus whatever they deem OK tolerance wise.

 

[Flogain]

OK, do your loaded round OD Is .3375”, and you wanna use a .334” bushing for .003” neck tension.

Your mandrel needs to be .305”, so get a neck turning mandrel, not a neck sizing mandrel. A neck turning mandrel is smaller in diameter. They are not exactly .305”, but plus minus whatever they deem OK tolerance wise.

And I don’t doubt your knowledge. But could you tell me why the .305 mandrel is what I’m looking for?

 

[918v]

You’re shooting a 308 Win aren’t you?

 

[Flogain]

You’re shooting a 308 Win aren’t you?

Yes, sir

 

[918v]

Then why would you want to expand the neck with anything other than a .305” mandrel if you want .003” neck tension in a .308” bullet?

 

[Flogain]

Then why would you want to expand the neck with anything other than a .305” mandrel if you want .003” neck tension in a .308” bullet?

Haha yep, makes sense. I needed to think about it. The numbers get confusing to me on occasion. I keep thinking .3375 and couldn’t figure how .305 fit into that

 

[918v]

A 334 bushing will size a little under that. If you measure the middle of the neck it will prolly be 333 and a 305 mandrel will increase it back to 334.