38/357 expander diameters.

[cbriggs57]

Anyone else ever disassemble a die set and take measurements of the pieces? I had problems with dirty/incomplete burn of Unique in my Ruger GP 100, and someone suggested I look at my expander to see if it was too big, causing low bullet pull and incomplete combustion. Lo and behold, the expander appeared to have never been finish machined by any acceptable standard, and the button (if you call it that) runs .007" eccentric from the expander body.
I'm a precision grinder by day, so I'm going to make a replacement from carbide and see if I can remedy the situation.
The original expander mikes .357 diameter. My bullets are .358 diameter. Thinking of making the expander .355 or .356. What do you use? What diameters seem to work for you? I'm open to suggestions and interested in your measurements, if you know them, and the results.

[454PB]

I like .002" smaller than the boolit size, so I'd want .356".

[wv109323]

.001 to .002 under the size of the sized Boolit.

[gray wolf]

My bullets are sized .358 -- I like .002" smaller than the boolit size, so I'd want .356".
NOT saying you do but --- low charges of Unique will burn dirty no matter what the bullet hold.
Expander size is some what dependent on bullet hardness and condition of case mouths.
Softer bullets have a hard time being compatible with a small expander, bullets get reduced in size.
make the expander bigger for soft bullets and you risk the bullet jumping crimp.
Increase the crimp to make up for it and the bullet has a hard time opening the crimp and you scrape lead off the bullet.
The harder the bullet the more neck tension can be used, but we don't always want to use a hard bullet.
For me I want enough neck tension to hold the bullet for a particular load, I want the crimp to open,
and when I pull a bullet it needs to be the same size it was when I seated it.