Bushing Die Expander Ball

[jschuerg62]

I've got a question about whether to use an expander ball with a bushing die or not. I am in the process of working up a
load for a 6.5 PRC. I've got an RCBS Gold Match bushing die. I have been doing a lot of reading on bushing dies and
trying to fully understand the advantages/disadvantages of using one and also if it is intended to be used
with the expander ball or not. My understanding is that most expander balls are sized .001" smaller than the
bullet diameter, which in my case (using a .264 bullet) would be .263". Sooo below are two examples of cases with different
case neck thicknesses which I am going to calculate the bushing size for (-.001")

Case 1 (.015" neck thickness)
Bushing Size = (.015 + .015 + .264) - .001 = .293
Case Inside Diameter = .293 - .015 - .015 = .263 inside diameter

Case 2 (.013" neck thickness)
Bushing Size = (.013 + .013 + .264) - .001 = .289
Case Inside Diameter = .289 - .013 - .013 = .263 inside diameter

In every scenario if you are sizing the bushing .001 less the inside diameter of the case ends up
being .263 which is, from my understanding, what most expander balls are (.001 less than the bullet). Am I looking at this
correctly? If I am I don't see the advantage in using the expander ball.

Thanks in advance for any feedback....

 

[Blue68f100]

Are you turning the necks? If so use bushing only. If your not pick a bushing size that allows minimal work for the expander. Most expanders are 0.002" under bore size.

 

[old heeler]

I've got a question about whether to use an expander ball with a bushing die or not. I am in the process of working up a
load for a 6.5 PRC. I've got an RCBS Gold Match bushing die. I have been doing a lot of reading on bushing dies and
trying to fully understand the advantages/disadvantages of using one and also if it is intended to be used
with the expander ball or not. My understanding is that most expander balls are sized .001" smaller than the
bullet diameter, which in my case (using a .264 bullet) would be .263". Sooo below are two examples of cases with different
case neck thicknesses which I am going to calculate the bushing size for (-.001")

Case 1 (.015" neck thickness)
Bushing Size = (.015 + .015 + .264) - .001 = .293
Case Inside Diameter = .293 - .015 - .015 = .263 inside diameter

Case 2 (.013" neck thickness)
Bushing Size = (.013 + .013 + .264) - .001 = .289
Case Inside Diameter = .289 - .013 - .013 = .263 inside diameter

In every scenario if you are sizing the bushing .001 less the inside diameter of the case ends up
being .263 which is, from my understanding, what most expander balls are (.001 less than the bullet). Am I looking at this
correctly? If I am I don't see the advantage in using the expander ball.

Thanks in advance for any feedback....

Problem you have, what is fired dia. That turn neck may be too much.

 

[Demi-human]

You are thinking of it correctly.

The bushing must size the case enough to have the expander open it to the proper dimension. It will take a different size bushing to accomplish this with different thickness of brass.

If the necks were turned the expander could be taken out completely (and it's compounded effect on runout) and only the bushings used. This would work the case mouth less as well.

Have you thought about an expanding mandrel instead of a ball? Pushing the mouth open is to be more consistent than pulling an expander ball through.

Though if I had turned brass I would only use the bushings.

Of course one can use bushings only with unturned brass as well.

Keep us posted on any findings.

 

[old heeler]

Reason You need to know fired dia first, if you used .289 bushing you don't want to size more than .008 of fired dia.

This is from Redding
it has come to our attention through customer calls and our own use of the bushing style sizing dies that in certain instances, a given neck sizing bushing will produce a case neck diameter that can be several thousandths of an inch smaller than the actual diameter of the bushing. This idiosyncrasy occurs when the neck diameter of the fired case is a great deal larger than the diameter of the neck sizing bushing, such as occurs when factory chambers are on the large side of the tolerance range and the brass is on the thin side. Typically, we have not noticed any problems until the case neck is reduced more than 0.008-0.010".

Lot of times factory chamber you better just to clean up the necks.

 

[jmorris]

Expanders can mess things up for sure. That’s why I always suggest checking fired cases for runout then every step of the way after that.

If a fired case is OK but you get runout after resizing, pull the expander, if that makes it better, the problem is your expander or lack of lube inside the neck.

There is also the fact that they are also different from each other, despite preforming the same task and some dies don’t even use an expander, rather a collet to compress a case around a mandrel (like the Lee in the center), then there are others that are only a expander die (like the Sinclair on the right).



Lots of size dies make things smaller than they need to be and, as the name implies, the expander makes the ID larger. If there are dings and dents they get “ironed out” vs just forced inward. If you don’t have a consistent wall thickness sizing to the same OD will only give you many different ID’s. The fact that most don’t turn necks is why most dies have expanders because that’s the easiest way to have consistent ID’s.

So, how do we know what will work best for you? Unfortunately we don’t know. I have used all of the above successfully.

You can spend the time and figure out what works best for your setup or if you are competing, you might find a mentor you would like to be able to beat and start by emulating his techniques.

As above, keep us posted though.

 

[jschuerg62]

I appreciate the responses. In your opinion what is an acceptable variation on the neck wall thickness and run-out. I currently turn all of my necks and
try to keep the runout under .002".

 

[jmorris]

It really depends on the barrel. On some of them that have “standard chambers” I don’t even turn the necks, just use quality brass.

The more material I remove from the neck just means it can expand that much more before it contacts steel, when fired and I have to move it back that much more to be able to seat another bullet with proper neck tension.

If I have a chamber neck cut “under” then turned brass is not a problem, necessary in fact.

You can always try it both ways and see what works best in your barrel and see what effects you get on case life.

 

[Varminterror]

Turned necks, use a bushing only, and live happy if you like.

Non-turned necks, use the bushing to bring it down slightly smaller than bullet diameter, and push it back out with an expanding mandrel.