Datum line for 338 Norma mag help needed.

[Charlie Bravo]

Hello all.

I've been trying to find out what the datum line is for 338 Norma mag, but unfortunately without much succes. I've tried using Forsters datum dial and i get a reading of 2.073 using the 0.420 hole. I can get reliable readings using it, but I don't know if the number is valid? I haven't been able to find any numbers for the datum line.

Is the .420 dial usable for getting my Measurements on a 338 Norma mag or do I have to get a custom one made for it?

Any help is appreciated.

 

[Fuzzball]

Charley, you don't say why you want the datum line but if it's for reloading, it hardly matters. For us it's a relative thing, all we need is a point of reference between fired and resized cases to confirm we are resizing the shoulders back to just equal or a tad less than the fired location; exactly where on the shoulder we measure to doesn't matter a bit.

 

[damoncali]

I'm not sure if there is an official spec. Neither SAAMI nor CIP have the cartridge listed. just use whatever fits.

 

[Charlie Bravo]

Ok, great. Thank you for the answers.

 

[Brasscow]

Technically I believe it should be .450, but i think you'll be fine with .420 if you're just needing to know how far to bump the shoulders.

 

[Charlie Bravo]

I got a .450 made. The reading isn't valid I guess, since it's of from the specs in Quickload and books, but it's reliable for measurements, so it works.