The question I have is why is there such a big difference between Win and Norma loads? There seems to be very little difference in case size. The Win max load is only one grain higher than the Norma starting load. I am using IMR 4831 and a 140 gr bullet.
Can anyone explain this difference.

Rad

It means, that the manufacturers are timid in USA. Lawyers make the reloading guides in your country.

Different pressure test guns with perhaps a different pressure measuring system (copper crusher vs piezoelectric), different lots of powder and you get a little different result.

any brand of brass can change pressures/loads. I have both Norma and Lapua brass for my 6.5x284 and I'm sure when I get to loading, I'll find differences.

The 65x284 Norma is registered with CIP the 6.5x284 Win isn`t backed by anyone.
The Norma chamber therefore is cut to exact specs as governed by CIP, the Winchester chambers have been cut according to whoever has made the reamers idea of what specs should be. It is no wonder the reloading books are a little leery of pushing the Winchester version too hot.

I see that you're an NRA menber, HerrMesser.

You can find the exact answer to your question and a lot more on the differences between the 6.5mmx284 Winchester and Norma chamberings in the October 2008 issue of American Rifleman, starting on pg. 42. Written by Aaron Carter, Senior Associate Editor.

Thanks guys for your answers to my question. Had been out for a few days so didn't know anyone had answered or not. I will know more on the loads when I get the rifle back. I knew looking at the drawings on Steve's Pages there was not much difference in them.

I bought 284 in winchester brass and turned the necks on them just a little .

onefunzr2
I evidently overlooked that article, will have to dig around and see if I still have that issue.

Rad