9.3 is spot-on here - Straight WW alloy will probably work, but at that high a velocity, I'd probably heat-treat them.
; At normal 'below 2,000fps' WW alloys in bullets are normally pretty hard without being brittle like Antimony. Hardened as 9.3 indicated, by merely dropping them form the mould into a bucket of water will bring the average hardness up to about brinel 25. The only trouble with these, is the hardness will vary from about brinel 20 to 31 or so. This really doesn't present a problem as they never do get brittle like the high antimony content alloys.
; Adding tin to the mix will help casting but they'll age-soften over time. I cast straight WW alloys without any difficulty, just run the moulds and lead at higher than normal temps and go for an evenly frosted ball.
; Beware that stick-on WW's are soft. The ones with the clips are the harder variety and brinel will range from about 9 on the soft side to 13 on the hard side.
; Since pure lead is brinel 5, you can see how relative the hardness is. I've driven a straight WW ball of .684" diameter only 466gr. completely through both shoulders of a moose. My buddy, with the .75 muzzleloading rifle, at a velocity around 1,400fps could not keep his .735" 600gr. WW balls inside a moose, no matter the angle. I don't think he had any Texas heart shots, but 1/4 angles form the front and from the rear always resulted in an exit. It takes pretty good penetrative power to exit 1/4" to 3/8" thick hide with a 3/4" ball.
; All said and done, I'd try some water dropped from the mould balls for accuracy.
: I drove my first WW alloy .684", 466gr. ball into a solid block of concrete about 4" thick, by 12" x 18"- about 75yards, impact maybe 1,300fps. The rifle used was my 14 bore English Sporting Rifle with 165gr. 2F. The largest piece was fist sized and I still have the ball - still in one piece, badly flattened and 440gr. I was absolutely amazed it didn't break up on that hard, old concrete slab.
: Sarg- I'm sure you'll enjoy further 'tests' of this nature. The 'power' is truely amazing. Shoot a big ungulate with one and watch them stagger at the hit.