Are the Cylinder Throats Oversize?

[bowfin]

I have a Herter's .401 Powermag revolver. Here are the measurments:

Slugged the barrel, and it measures .402"+

The throats on the cylinder are .406"

My mold from Accurate throws a boolit that is between .403" and .404"

Are those throats somewhat oversize?

[stubshaft]

Yes they are. Just size the boolit to .403 and shoot them, there isn't much you can do about it and accuracy should still be good.

[leadman]

Can you modify your alloy to increase the diameter? Maybe some more antimony?

I have changed drop size by as much as .002" from some molds by adding antimony or lino.

[44man]

You should be fine. I have never found a boolit has to fit the throats exactly. Groove size to .002" over is all you need worry about.
Load the brass right and I bet it is a 1" shooter at 50 yards.
Those were pretty decent guns.

[Larry Gibson]

You should be fine. I have never found a boolit has to fit the throats exactly. ..............

+ another on that!

Larry Gibson

[Hang Fire]

+ another on that!

Larry Gibson

Ditto on that, that is why the barrel forcing cone is called, a forcing cone.

The cylinder throats undersize to the bore is a much more common problem and "LEADs" to all sorts of problems

[pdawg_shooter]

Bump them up to whatever size you want. Just like sizing down but the other way.