Pardon Me --- Bears Repeating !
[quote=greydog]I have worked with cartridges of similar size but different shapes and am sort of convinced that case shape doesn't mean a lot but some cartridges are certainly more consistently accurate than others.
One group of cartridges were all 30 calibers (sort of). The 308 Winchester, the 303 British, the 30/40 Krag and the 300 savage. All are about the same size. One has a real long neck (30/40) and one a real short neck (300 Savage). The Savage cases was smallest but the other three were very close. Close enough that the brand of the brass would change the ranking. All of them were built as accuracy rifles though the rimmed case rifles were a little less conventional. The 308 and the 300 Savage liked 4895 and 150 grain bullets with the 300 using a couple of grain s less. Both cartridges were used in a Remington 40xBR and used the same Hart Barrel. Both would shoot right at 1/4 moa and both produced the occasional group under .2. I was never able to manage a .250 aggregate with either one because of fatigue, I suspect. This was a 10 1/2 pound rifle and recoil was a factor.
The 30/40 was built on a Ruger 77 and the 303 on a considerably modified P14. I shot 168's in the 30/40 and 174's in the 303. Both rifles seemed to be capable of shooting right at the .300 moa level with the occasional group under 1/4. They also both liked 4895. That the rifles did not shoot quite as well as the 40X is less indicative of any shortcoming as far as cartridge design is concerned than it is indicative that the 40X is a better platform than the Ruger 77 or the P14. By the way, both the Ruger and Enfield used three-lever, 2 oz triggers; a Canjar on the Ruger and a homemade unit on the Enfield. The rimless cartridges seemed to be easier to work with and brass was a bit better.
The other cartridges were the 6x47 Remington and the 6PPC. The 6x47 was built on a 40XBR and I used it a lot, wearing out three barrels. It shot very well and I was able to agg under 1/4 moa whenever conditions and my brain would let me. I won a lot of stuff with that rifle but it was a little bit fussy. I built my first PPC in 1980 and while it didn't shoot an awful lot better, it was so easy to develop a load for, it was almost hard to decide on which components to use. In this particular example, I think there is no question the PPC is better than the 6x47. So is the 6 BR. Whether this is because the cases are short and fat, or because they have 30 degree shoulders, or because they can be loaded hotter without dropping the primer, I can't say but, there it is.
When I started shooting "F" class, I shot a 6.5x55 and had pretty good success with it. I built a few 260's and they worked fine too. Nonetheless, I think the Creedmoor might be better than either one. A lot of this may be due to closer dimensional consistency of reamers and brass.
In the end, I can say that most cartridges seem to work just fine and the rifle is more important than is the cartridge.
GD
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THANK YOU !
Jerry
