Flash hole uniformer

[flattail]

I just bought some new Winchester 45-70 brass and it looks like the primer flash holes on some of them have a slight flat side to them.  Is that a concern?  Is that what a flash hole uniformer is used to correct?  Do I need to worry about the possibility that I might enlarge the hole trying to "uniform" it? I don't even know for sure what a flash hole uniformer looks like (I assume like a small reamer).  Also, I have seen posts where reloaders talk about a primer pocket uniformer.  What might that be?  Any help would be appreciated.  Thanks.

[PlacitasSlim]

I use a lyman flash hole uniformer which looks like a small thin center drill screwed into a wooden handle with an adjustable tapered case stop on the shank. I use this from the inside of the case. The primer pocket uniformer I have has 2 small blade that cuts the bottom of the primer pocket to a uniform depth. It is used on the outside of the case. On any case I am loading for accuracy, I do this before the first loading. I normally do this on all my 45/70 cases.

[beemanbeme]

I would be curious for you to take some of the cases with obvious flaws and load and shoot them, as is, against some that you had uniformed. 

[OLDHandgunner]

I use a flashhole tool & the primer pocket uniformer from Sinclair to do all my rifle brass before I load them for the first time. This makes the flashholes uniform size & deburres them from the inside. The primer pocket tool makes all the pocket the same depth. Anything for a little more accuracy. It takes a little more time the first loading but usually it don't have to be done again.