Can someone tell me what the difference between the 6.5-284 Winchester and the 6.5-284 Norma is?
If I rechamber my target rifle for 6.5-284 Winchester, can I use the Norma brass?

The 6.5-284 Winchester was the wildcat version, and the 6.5-284 Norma is the "approved" CIP version.

Basically they are identical except for one minor little detail.

The Winchester has a head-to-shoulder length of 1.775" and the Norma is 1.7581".

I want to rechamber my 6.5x55 target rifle for something with more velocity because I'm lucky to get 2800fps with a maximum load, even through a 30" barrel. The 6.5-284 Norma appears to be the best choice for rechambering because it's the only cartridge in this calibre (non-magnum) with a head diameter bigger than the Swede's.
The reason I posted my question is I can get dies for the 6.5-284 Winchester at a better price than the Norma, but I'd like to use the Lapua brass. I can get this brass at a good price, plus there is much less case prep than if I neck down 284 Winchester brass.
So, if the chamber is cut with a 6.5-284 Norma reamer, it will have 6thou' more headspace than with the Winchester reamer. Is this headspace excessive if chambering cases formed with the Winchester full length die? This would also necessitate using different headspace gauges.
Cutting a Winchester chamber and then full length sizing the Lapua brass before firing would solve these problems.
But what about neck sizing with the Winchester die? Is the neck narrower in the Norma chamber? Is it wider in the Winchester chamber to accomodate necked down brass? It might seem like I'm beginning to split hairs, but a well made concentric round is important at 1000 yards. And I like to outshoot the guys who think it can't be accurate if it cost less than a week's wages to load for one calibre.

Oops! I apologise for misreading the figures. The Norma is 16.9thou shorter. Is this excessive headspace for chambering the Norma brass?

The difference is manufacturing tolerances. Norma makes their cases about 0.004" larger at the head than Winchester.

Winchester cases are a sloppy fit in a Norma chamber and show a pronounces pressure bulge. Some Norma brass will not go in a Winchester chamber.

I got into this mess here a while back when ordering my own reamer. I chose Norma because of the brass quality. I started this project in order to get a tight necked reamer. Geo.

neck chamber of Norma is 0.297 neck of 6.5/284 win ( JGS) is 0.301 and base diameter are not the same

best way to rechamber a 6.5x55 is to use 6.5/284 win JGS to get closely the same neck dia and use thicker 6.5/284 win neck to avoid to much neck expansion .

good shooting

DAN TEC

[ 06-24-2003, 10:52: Message edited by: dantec ]

Thanks Dantec. I've just ordered a 6.5-284 Winchester reamer and dies. I've also ordered Norma brass as well as Winchester 284 brass. If the Norma won't chamber I'll try full length sizing it. If its neck is sloppy I won't use it. I've also been told that the Norma case is 17thou' shorter from head to shoulder, so I'll neck it up to 7mm then size it to leave a bump to headspace on before fireforming. All this just to avoid the case prep for Winchester brass? I'll try them both... it's a hobby!