Can anybody explain what the difference,s between the
two are?
The major difference is that the Norma is a SAAMI approved factory cartridge and the Winchester version is still a wildcat based off the necked down .284 Winchester case.
The exterior case dimensions are within a few thousandths of each other.
SU35 is right, the Norma has a COL of 3.226" and is therefore ill suited for use in a short action.
http://www.6mmbr.com/SixFive284.htmlGood article on the 6.5 x 284 If you are interested to read on. Don't use the loads mentioned in the article. These are way hot in my Savage 12 F.
There are several differences, the biggest being the freebore in the Norma chambering. The neck is tighter in the Norma and the base smaller in diameter. The Winchester version is quite generous in some dimensions and has a short throat. They are "basically" the same but with those subtle differences.
378 that is a very good link.Answered alot of my questions