I may be the one, but I think there is a lot of un-due confusion on this topic.
I think that a 338-06 or a 338-06 A-square or whatever unless it is an ackley improved is the same thing, a standard 30-06 necked up to 338 and nothing else.
You never hear someone saying that a 30-06 and a 30-06 springfield has a different shoulder angle. I think A2 as some mentioned above is just the name of who standardized it not a different cartridge.
The 30-06 and 338-06 have a shoulder angle or 17degrees and 30 minutes or 17.5 degrees if I remember my math. LOl
some others that have the same SA include the 25-06, 270, 280, and 35 whelen and maybe some others.
I hope DZ will chime in on this one, he would know.
