Hi, Chuck,
The wheel weights I'm now using end up in the 12-14 BHN range when air cooled. Dropped into a bucket of cold water, they go to 18 BHN or so. Wheel weights make tough bullets while linotype makes brittle bullets. WW's seldom shatter while LT tends to do so if bones are hit at higher velocities--like 1800 and up. I usually add one pound of linotype to three pounds of wheel weights because the linotype helps the castability and mould fill out. If I don't care to use lino, I turn the heat up on my RCBS Pro-Melt to 850 degrees and allow more time for cooling between fillings. I should mention that I add linotype only for the cb's for my 308 when I want to run them over 1800 fps and for magnum loads in 357 and 44. If your barrels are smooth, wheel weights should do nicely even without gas checks. I've recovered only two cb's from all the deer I've gotten. A 170 grain 30-30 that went from the third rib to the skin under the right rear ham (it was right beside the tail) at a distance of 50 yards and a 200 grainer from my Marlin 357 that went through about 18-20 inches of venison and shattered the ball joint of the right shoulder at a bit over 100 yards.
Bottom line? Try the wheel weights. If they seem too soft, heat treat then or just drop them in a bucket of water (I use 1 inch squares of carpet underlayment foam about 3 inches thick floating on the water to keep the splashing down and to slow the hot cb's a bit.) Have had good luck with this for 30+ years now. Happy casting!