ORIGINAL: Sling
How is it possible that the fastest 200 grain load is faster than the fastest 180 grain load? And why is the same 52 grains of IMR4350 pushing the 200 grain bullet faster than the 180 grain bullet?
Jason certainly has something there, and it goes along with the following idea, which is based on both powder burning rate and cartridge case volume:
I suspect the reason for this is that the 52-grain load is
more efficientwiththe 200-grain bullet (gets the most out of the amount of powder) than with the 180-grain. I'll bet that you could use MORE than 52 grains of IMR 4350 with the 180-grain bullet, and get even higher velocities,
IF you could get more IMR 4350 into the case and still be able to seat a bullet! But since the case doesn't have enough room to try this with IMR 4350-sized powder grains, you will never know!
However, if you tried this test with WW 760, H414, or even Norma N204 powder, all three of which are dense enough to allow you to put a heavier weightthan 52 grains into the 8X57JS case, you could give it a try. Of course, you'd have to start with like 50 grains of any of these, and work up no faster than 0.5 grain at a time, load up five, and chronograph them as you worked up, making sure you got no loosening primer pockets while doing it. You might be surprised at how fast a 180-grain bullet can be SAFELY driven from a strong 8X57mm, IF the right powder is found.
(No, I don't really know. I have only worked with the 8X60RS, which will let me put in more powder w/o compressing the load. With one load, I was able to get 2620 FPS with 200-grain Nosler Partitions.))