See there, little brother, the .36 (and the .32) are not only heavenly accurate but also easy to feed, plays well with others and ain't picky. Since supplies are expensive I tend to shoot the little guys the most. Next up is the .45 but that's still a noticeable jump. Generally my powder charges for the .36/.32 run 20 to 30 grains. I still experiment with tiny charges of 12-15 grains (not able to do that now) but more needs to be done. I find it very pleasing that much thought and experimentation are going on to find just the right rifle by customizing & parts.
I've killed a fine deer total (and small game) with factory & kit, some second hand and some forgotten rifles. I recall using a CVA .50, Traditions .50, Traditions .32, Pedersoli .50, Numrich Arms .45, Euroarms .54 but there are more. But one can be into muzzleloading only so long before FLINTLOCKS, many of them hand-built, invade your home. I've used flintlocks exclusively for quite a few years. The last deer I killed with percussion was a doe I dropped with my (heavy but tack driving) US M1841 .54 prb.
For a long time I used rather "unnecessarily" heavy loads for hunting. For .45 I used 80 grains of 3F in flintlocks (65 grains in the H&A Under hammer) and 100 grains in anything .50. So the velocities the deer endured I can only guess. I do seem to recall chronographing my 42" TVM VA .50 with 100 grains of 3F. No, I can't remember it well but do seem to recall over 2100 fps.
After years of learning useful (hopefully) stuff about muzzleloading I think I have a good idea about deer loads. IMHO the ideal velocity range in the .45 and .50 is in the 1600 fps to 1800 fps territory. And 1400 fps will do just fine. Over 1800 might be a good idea for 100 yds plus shots. One thing is for sure, the bigger the ball the less velocity needed. Example: .600" prb from a smoothbore at 1200 fps hits like the hammer of Thor. And the first rule of the 5 absolutes is that there is only ONE (1) degree of dead.