Re: 7 wsm vs 7 rsaum-- that is the ?
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awesome work, this is exactly what I was looking for. mathematical equasions are great for forming a solid basis and are essential, but on the otherhand they are not absolute and do not account for variables such as efficiency and other factors. (most AI cases claim 150fps velocity increase and the case capacity is only increased from 8 to 12%). the bottom line is you have to study things out ballisticly,mathematicly then go shoot it through a chronograph to filter out the feces.
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Take the Nosler #5 manual... average the velocities for the top 3 loads in the .280... then average them for the .280 AI and you see an increase of around 3%. This is right inline with the math supplied for us on this very post (and made famous by John Barnsnes), velocity increases (3%) at 1/4 the increase in capacity (12%). Do it again with the .30-06 AI data, and the .22-250 AI data in the same manual and you'll see the same trend. This data was shot in a lab, using SAAMI pressure specs for the given standard cartridge. You do see slightly more than 3% as bullet weight increases... but it's still around 100fps. Now, given this data it's hard to believe that simply lengthening the throat would enable one to reclaim enough powder capacity to generate AI type gains. I love my AI... and I see significant gains in velocity... but I always tell folks it's because I'm able to shoot the round at higher pressure due to the benefits of AI case design... not because I can fit a little more powder in it. Again, I don't doubt that you see the kind of velocities you do... I just doubt that you're within the same pressure limits, and I doubt that the extra couple of K/PSI really matter in the whole scheme of things. But, I think we should just call a spade a spade and recognize that it takes higher pressure to make stuff go faster out of the same case... regardless of the throat length (within reason). Oh, and what barrel length/make do you shoot in the custom 7WSM with the LONG throat? ~JT
UB: I truly enjoy discussions like this... they're both informative and educational. I appreciate the fact that you read the article I mentioned before responding, and I like the "bottom of the birdcage" line... I ask your permission to use it at work.
Dirty Dogs... Down Dirt Cheap!!!