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9.3 Rock
Posted by steveinmi on Jan 26 2006
kablewy,
Thanks for your comments. You're not stepping on my toes - you ask good questions, I could have been clearer, and I always like to exchange info w/ folks interested in some stuff that's a little different, particularly 9.3mm.
First, you are absolutely correct, SAAMI spec is 3.340" for the 30-06. My saying 3.4" was sloppy, even though the vast majority of rifles will take rounds longer than SAAMI specs. It's the old mass production "max ammo size within manufacturing tolerance vs. min chamber dimension within manufacturing tolerance" issue.
There is no SAAMI spec for 8x68. It is controlled under CIP specs. Head size is listed variously as .511 or .512. The German reloading manual, "Wiederladen" lists it as 13.00mm, or .51181" by the conversion factor I have. When I referred to the bolt face, I meant the you can do the 9.3 Rock rifle on a standard action. There is no need to go to a magnum sized action or bolt.
Water capacity of the 338 Win Mag is 84.9 gr (my measure - Barnes lists it as 85.6; there may be a brass thickness difference). A 9.3x64 Brenneke case holds 85.6 gr (my measure). Water capacity of the 9.3 Rock is 92.8 gr.; 80.4 gr to the base of the neck. The neck is .410" long.
With different bullets seated, the 9.3x64 Brenneke case holds 65.7 - 71 gr. of water, depending on necessary bullet seating depth. The 9.3 Rock, with bullets seated to a C.O.L. of 3.475" holds from 74.5 gr to 82.3 gr of water, depending on the bullet.
While the difference may not be significant, I preferred a beltless case. Without a belt, that diameter can be used for case capacity. On the 338 Win Mag, the case body just ahead of the belt is .513". The 8x68 is .524". And I just don't see any reason for a belt - nothing wrong with it, I suppose, but it doesn't serve any real purpose. The 9.3 Rock case is .510" at the base of the shoulder, as compared to the .491" of the 338.
I can only report what the lab reported to me regarding velocities and pressures. I wasn't there to see it done. Here's a sample: Swift 250 gr. w/ 84.0 gr. IMR4350, 3,001 fps at 55,850psi; Speer 270 gr. w/ 83.5 gr. IMR4831, 2,871 fps at 53,050 psi; Swift 300 gr. w/84.5 gr H4831SC, 2,703 fps at 50,00 psi, and 2,692 fps w/77.5 gr IMR4350 at 50,550 psi.
Hope that helps answer a few of your questions.
Steve
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