I've shot some big lead (460's and 488's IIRC) in my converted Knight .45 cal 1:20 twist and my White M-98 in .451 cal 1:20 twist w/209 conversion with Blackhorn 209 back in 2008 or 2009, but I cannot remember how high I went on powder. Would probably be in the 70-80 grains by VOLUME, which would equate to 49-56 grains by WEIGHT. I tested some 460 grainers in my .45 cal Slufoot Super Smoker (smokeless capable) 1:20 twist back in 2011. I have also shot 440 grainers out of my .502 cal Knights and .502 cal NEF Huntsman 1:28 twist with 80 grains by VOLUME with excellent results. I did a lot of shooting, and testing different breech plugs and primers with Blackhorn 209 back in 2008 and 2009. I prefer my lead bullets sized .001" over the bore (lands) diameter, and use 1 or 2 Vegetable Fiber Gasket Wads, depending on what the load likes. I'm not recoil sensitive, and if you have ever shot a 3-1/2" 12 ga turkey load at a target more than once, you probably aren't either.
Someone mentioned time/pressure curves. Blackhorn 209 is not all that much different than Triple Se7en Loose Powder. Pellets are a whole nuther animal. Especially cracked/broken/crushed ones. Each horizontal line is another 5,000 psi.