DCR,
If you really want to shoot conicals in the Huntsman, don't mess around (waste your time and money) with the light weights. Get some in the 400 grain to 490 grain range. The 460 grain No Excuses or Bullshop are some of the best conicals available. Bullshop has a much wider selection, can size them from .499" to .5045" and are very reasonable. You will want pure lead, # 2 lube, sized at .503" for a slip fit. You will get slight engraving, the bullet will stay seated, and will obturate fully into the grooves upon ignition. You can load and shoot these bullets all day long without swabbing between shots. Bullshop also has a new bullet that a very savvy gentleman in Missouri designed called a UC Short, it is in the 440-445 grain range, I haven't tried it yet but should be about the perfect bullet for the 1:28 twist. I have read some good reports on that bullet performing well out of the Knight which is virtually the same barrel as my Huntsman (same rifling), both being made by Green Mountain.
You will only need about 70-80 grains of powder (I use 80 grains 777 FFFG) with these bullets, and I also use a .518"x.60" fiber gasket wad (not necessary) for better accuracy. With a scoped barrel I have shot these under MOA, with a peep sight 1.5" - 2" groups at 100 yards with the right conditions. I will try to PM you the information for Bullshop (Dan) and No Excuses (Dave), either one of these guys are great to do business with. Bullshop uses the flat rate shipping from USPS, so you can get alot of lead shipped (several boxes) for the same rate. He can send you a sample pack for a very reasonable price to if you ask.