Flattened case mouth remedy

[Gunnysgt]

After thinking this out I came to a remedy that to most of you may be all too elementary
> Virgin brass all prepped, no necks turned. I choose to turn necks after once fired.
> Hand loaded 40 rounds with min.charge of 23 grains with Vit N133 powder and a 50 grain nosler bullet
> Fired all 40
> Discovered flattened edge of case mouth on all while extracting carefully so as not to let any fall on ground.
The easy fix is:
> Run brass in a FL sizer die and use the expander button to round out mouth and decap primer....(not a bushing die as this leaves a bump close to shoulder and causes a problem turning)
> Button leaves case mouth exact dimension to go straight to the Neck Turning Mandrel.
> Once turned, case goes to Bushing Die with correct bushing and continue loading from there on.
> Now after firing these rounds, I will still have flattened mouths and will use a 6mmppc expander mandrel by hand to gently round out the mouth before going to the FL Bushing Die and so on.
ANY COMMENTS APPRECIATED

 

[former naval person]

Sometimes that will work. Sometimes the expander button on the die does not correspond to the external diameter of the neck turning pilot. I find I have to use a K&M expandiron to enable smooth turning with my Forster neck turner. With so many different manufacturers out there doing the same procedure but by different machinery, you may have to experiment to get the fit right. You want a close fit, little "slop", and NOT a drive fit into the case mouth.JMHO

 

[Gunnysgt]

I understand what you are saying. Seems the Redding expander button with the die makes for even a tighter fit on the Sinclair turning mandrel than the
Sinclair expander mandrel does. Sinclair states their Expander mandrel is 0.001 larger than their Neck turning mandrel.

 

[gstaylorg]

On virgin brass straight out of the box, or fired brass that has slight flat spots in the necks due to a strong ejector spring, I use the Sinclair expander die with the oversized expander mandrel. Although flattened necks are not "perfect" after the expander die, they are close enough that the resizing die can finish the job. I have not observed (or at least been able to measure) any issues with neck concentricity after these two steps using the Sinclair concentricity gauge, so it appears to be working. I should also point out that not all of my rifles generate the flat spot upon ejection. For those that don't, the expander mandrel won't really do anything to fired brass as the hole is ever so slightly larger than the mandrel.