338 Whisper #2

[cherokee]

As far as I know the 338 Whisper has never been built on an AR15 platform. The 300 Whisper was designed for the AR15 and it works very well. If you want a 338 Whisper in an AR then you will have to go with the AR10.

[AR15barrels]

You would not actually headspace the 338 #2 on the rim, but on the case mouth.
Headspacing rifle cases on the mouth just sucks.
The case is long enough that length variation from firing and sizing becomes an issue.
We don't see these problems with pistol catridges like 9mm or 45 or with the 30 carbine however because the cases are generally thicker walled and don't change lengths as much.
Also, many pistol extractors do in fact control headspace, even though they are not supposed to.

If you want a 338 in the AR-15 action, get one of Marty's 338 Spectres and call it done.
6.8 SPC magazines, 6.8 SPC bolt and 10mm mag cases are all easily obtainable.

Randall Rausch
www.ar15barrels.com

[Greywuuf]

I agree headspacing on the case mouth sux ( rifle or pistol) but.... if you wanted to do your own reamer, you could cut down .223 brass and have a substancial amount of "mouth" thickness to work with. This of course gives you a much thicker neck and the atendant problems, you would have to religiously trim your brass, and not inadvertantly 'bevel" them with your deburring tool. just consider it a AR in 45 acp (or 9mm) the nice thing is that straight cases lend themself to volume reloading on a progressive press.