RCBS expander ball

Fireball Guy

New Member
Jan 8, 2010

I have just bought an RCBS neck sizer die for my .17 Rem Fireball and I must admit that I am disappointed by the finish on the expander ball as it is not the polished, ball-bearing like, button that I was expecting.

The RCBS ball appears to be machined from the same material as the rod and has machining marks running around the face.

I don't know whether this normal and if it will make any difference when reloading for a factory rifle ?
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Hey Fireball,

Unfortunately, yeah, that seems to be pretty normal. I've always looked at expander balls as necessary evils, at best. I prefer to use mandrels (like the Sinclair) whenever possible, with a carbide expander ball as a next best alternative. A polished carbon steel expander ball (like yours, after you've polished it) is the thrid choice, with an unpolished expander ball coming in dead last and a nearly unacceptable final option.

If you can't replace the ball with a carbide part, then it needs to be polished, at the very least. Very fine crocus cloth, 320-400 grit or so, is the stuff to use. remeber, you're not trying to alter the dimensions any more than you absolutely have to. You just want to "shine" it up a bit to make for easier passage or less drag during its passage through the sized neck.

Hope this helps, but if there's any questions, there's plenty of help right here on the boards.

Kevin Thomas
Lapua USA
Thanks for that.

I've checked the RCBS site and can't find a carbide expander for the RFB.

So, I'll try giving it a polish. :)
Hornady makes carbide expanders for RCBS dies, and I use one in my .223 dies. Unfortunately, .224" is the smallest one they make. I routinely polish all expander plugs whenever I buy a set of dies; almost all of them, from all manufacturers, need it.
I agree with Kevin. Just polish the ball, do not reduce the diameter

Expander balls are no longer needed with bushing dies now on the market. An expander ball can pull the shoulder forward and it can force the neck to one side losing concentricity. Ain't worth it for my money, to buy anything except bushing dies.
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