If the brass you are using and reloading is consistent at .045-.047", disregard the print dimensions.  .051" rim cut will work just fine.

The multiple sources of “new” (as of a few years ago), as well as some of the old stock, which could also vary some, makes these obsolete cases a law unto themselves.

It’s very common to find shells made toward the end of production due to obsolescence with dimensional variations that would give the SAAMI people the vapors. I’ve noticed it in the lengths of late production .32 Long Colt and .32-20, before the latter’s revival.  By that time, few people bought the calibers and precision production was not a priority; hacking the old slow-seller out, getting the dies changed and the production switched over to the latest hard-hittin’, brush-bustin’, wind-buckin’, tack-drivin’ marketing effort was top priority.  Some Bertram brass has only a nodding acquaintance with dimensional drawings, dimensional differences abounding even in the same box of 20.

I got some surprisingly good repro .25-20 SS decades ago from a place called Nelsdale Gun Shop that even so had varying rim thicknesses. I made a collet chuck by chambering a piece of barrel, sawing it horizontally into four “leaves,” threading the outside for a screw-on closer, “chambering” the shells in it on my lathe and thinning the rims to two different thicknesses.  I separated and used these in two different .25-20 rifles with different rim seat depths.  Still use the stuff, in the different rifles, and wish sometimes I’d bought more.  The Bill Ballard .25-20s, made from .223 brass, had very thin rims, but the shoulders fireformed out OK.  No headspace problems; the shells typically ended their service life by cracking along the sides, probably due to the stress on the brass in forming.

So I would second Mr. Louis’ advice to set your rim seat by the thickest rim you have.  If you are still on the scout for cases, you might give it a few thousandths extra, just in case.  After fireforming, nick size only and you should be fine.

I did cut the rim to fit the brass I have but was having second thoughts.   

I’m working with both Winchester and Bertram brass, have some that is buried and can’t get to it currently and not sure what it is.  I have about 250 rounds total.

The rims on both the Winchester and Bertram measure the same.  The rim diameter on the Winchester in .010 larger than the Bertram.  And, for what it’s worth, both bases are the same diameter just in front of the rim.

Since it’s not my reamer, I have options if I run into issues in the future.  I can turn the head down as bent said or in the extreme, single point the rim depth deeper in the lathe.
Thanks
Bob