I have a Cooper M52 with a Norma chamber. Looking at load data there's about 10% difference between Hornady/Sierra versus Nosler. The Sierra clearly states it is Winchester data, and the Nosler clearly states it is Norma data. Could that be right, is there a 10% difference in powder capacity between the two for 140 grain bullets?

D.

Yes, welcome to Earth and the real world. Reloading data varies from maker to maker. Ten percent? Sure. Why? All the variables that go into rifles and ammo, or not.

Sorry, the question wasn't detailed enough. BTW, not to boast but I've been doing this for 35 years, I surely know about differences between makers, I was trying to focus in on the two chamber cuts, both in 6.5x284. Sierra (and maybe Hornady) base their data on the Winchester dimensions and Nosler bases their data on the Norma. The chambers are EVER SO SLIGHTLY different (you can chamber rounds back and forth between the two), and when you look at the differences of the 140MK and 140CC which are only in the ogive (one is tangent, other is secant), I wouldn't think max load would be 5gr different, maybe 1-2 at most. Maybe you have to be familiar with the cartridge to understand or appreciate the question.

D.

6,5*284 is a wildcat it can be loaded to any pressure level you like. 6,5*284 norma is a standardised cartridge.

There are slight differences in the chambers as shown in these drawings. The cartridges are not the same and that likely shows as the difference you are seeing in data.


6.5x284 Winchester
http://stevespages.com/jpg/cd65x284winchester.jpg


Norma version
http://stevespages.com/jpg/cd65284norma.jpg

I seriously doubt there is 10% difference in them. I have been running the Winchester version since before there was any data on it. I guarantee you that you don't want to know what Sierra's first estimate of load data was. I would treat it like any other cartridge and just find as much info as you can and work up from there.

Larry, by chance are you shooting 140 amax or matchkings, if so are you using reloader 19 or 22 and in what charges?

D.

I doubt the difference is case capacity caused by that slight drawing difference.

Bullet shape, OAL "Lawyer Input" as to max pressure.

Deke, I have tried both with a Sierra 140 and 142MK. As I recall, with 19 and 22 the best I shot was with 47-48 grains, but those bullets are very long, so they may take up space in the case so work up slowly. I actually had better luck with the 120MK and AA4350. I don't try to push things to max. That's what I have the 264WM for.

If there are any differences they do not come from the chamber. The throating of the two versions might make some difference and is not shown on the drawings. Then again many people building wildcats specify their own throat design.

Headspacing of the 6.5-284 and 6.5-284 Norma is identical when comparing CIP and SAAMI prints.

The cartridge print shown in Steve's pages would have in excess of .015" headspace in a chamber headspaced to minimum spec, while headspace of the 6.5-284 (Win) cartridge would be nil.

Whatever chamber is used, it's important the loaded round fit the chamber correctly, with minimal headspace.

quote:

Whatever chamber is used, it's important the loaded round fit the chamber correctly, with minimal headspace.

This is the most important thing to remember...

It no so much case capacity as it it OAL. The 6.5x284 Norma is 3.228" vs 6.5x284 @ 2.800".

Nosler manual has loading data for the 6.5x284 Norma

In my opinion Sierra and Hornady data tends to be overly cautious while Nosler appears more overly optimistic. I dont conclude that from any particular round, it's just my overall point of view. But there are plenty exceptions.

This discussion has me intrigued.
It's quite simple to explain the difference between load data of the 2 chamberings, it's all got to do with the COAL difference and the throat length. The same reason why a 270 Weatherby chambering digests over 10% more powder than a 264 Win Mag, very similar chambers, but vastly different throats.
My suggestion, if you have a Winchester wildcat, DO NOT USE NORMA DATA, it WILL produce higher pressure in the shorter COAL and throat.
You CAN use Winchester based data in your Norma chambering, but it will be slower in velocity with mild pressure.

Hope this explains the difference adequately.

Cheers.

quote:

Originally posted by tom holland:
It no so much case capacity as it it OAL. The 6.5x284 Norma is 3.228" vs 6.5x284 @ 2.800".

Nosler manual has loading data for the 6.5x284 Norma

And, here is the winner!