Please parden me if I'm way off base here and I probably am comparing apples to oranges, but I too bought into the small caliber must be hard alloy theory..but for a differen't reason. I have been shooting cast in the .22's for years and found extreem hardness wasn't necessary for accuracy. But when I started to work with an original 1895 Winchester-Lee straight-pull sporting rifle chambered for the .236 (6mm) Lee-Navy, my concern was for the fast 1-71/2" twist. So I cast up some hard Steriotype Ideal 245495, as well as some cast of range scrap. My biggest headache came when I found the throat to be .0005" UNDER groove dia!...with a very long throat..so long a bullet held in case neck only by gas check still didn't reach rifling. I finally had to size bullet to groove dia., size first two bands .001" under bore dia. in order to prevent bullet from being pushed back into case as action was closed. The gas check did spring back to .001" over groove dia. so I was hoping it would at least seal the bore. Lyman Super Moly was used and bullets were tumble-coated in Moly before lubing. Since this rifle has an open buckhorn rear and german silver front blade, I decided to do testing at only 50yds. I first tried H4227...10.0gr. shooting to sights and giving 3/4" groups. I then tried TrailBoss..interestingly..a 10.0gr. charge also shot to sights with 3/4" groups. All the H4227 loads..including heaver charges that opened groups to patterns left case necks blackened. All TrailBoss loads, including the very light starting ones, left case necks clean..also muzzle blast was less using TB. I used the range scrap bullets for these tests and there wasn't a speck of lead in the bore...this rifle hasn't been shot much and bore is very bright and smooth. I did move back to 100yds and was getting 1 1/8" groups which I didn't think too shabby for open irons and 60+ year old eyes. A Gehman adjustable iiris diopter on the shooting glasses really sharpens up the sights. I never did get around to using the hard stuff. I admit 10grs. is a pretty light load, but I was only after accuracy. I know my rifle isn't anywhere near the same league as your scoped modern rifle, but it;s interesting that we both found a softer bullet works in a 6mm. Yours is a very interesting project, I look forward to reading more.