I shoot full bore .50 lead conical slugs in my cheap Traditions break-action muzzle loader, typically over either T7 or Goex FFg, often with a felt WonderWad between powder and bullet. Accuracy is, as has been lightly touched upon by an earlier poster, tuned into the load. Just because the rifle can shoot 150 grains of powder doesn't mean it should shoot that much. I've found accuracy comes in several "nodes" - in this rifle 70gr FFg is absolutely the most accurate load, followed by 90gr FFg. By the time we get to 110gr FFg the groups are opening up. At 150gr FFg one might just as well consider the rifle to be a 25 yard gun for responsible game harvesting. More powder is not better.
I've recently come into some Blackhorn 209 which will be used in accuracy testing in the future.
I've never had anything like accuracy from any of the pre-measured powder loads, sticks or pucks - they tend to break down unpredictably as the projectile is seated, thus rendering moot any attempt to achieve consistent seating pressure. Consistent seating pressure is one of the key ingredients in achieving good accuracy in any muzzleloader.
With a 90 grain charge I would very happily attempt a whitetail out to about 125 yards - after that I would be concerned about retained energy and lack of lethality. I would NOT be concerned about accuracy as my rifles print well out to 200 yards.
By comparison, I have an Ithaca Model 37 Deerslayer in 20ga. For plinking I shoot Remington Sluggers through it. The design of this slug gun is excellent, making the shooting of slugs actually enjoyable rather than the miserable, punishing experience more commonly associated with slug guns. Shooting prone off my elbows at 50 yards, three shot cloverleafs are common. Oddly, group size opens up as we approach 100 yards, most likely as a result of wind effects as the slug rapidly drops velocity. Still, at 100yards this would be a highly lethal deer gun. I'm not sure I would want to stretch it past 125 yards. Again, I tend to favour guaranteed lethality over bragging rights on long shots.
Like others who have posted here, I don't have the desire to shoot very expensive sabot loads. For me the benefit of frequent range sessions with multiple training shots far outweighs the value of a potentially better bullet found in a sabot.
Oh, I should also mention that my most successful deer kills have been at ranges below 50 yards with (again!) a cheap Traditions Hawken-style rifle shooting a patched round ball. In fact the first deer I harvested with that rifle literally stood over top my 50 yard distance marker! That rifle is deadly accurate with 70gr FFg, a .490 Hornady ball and a .010 Wonderlube patch. When I say deadly accurate I'm talking group sizes at 50 yards which are difficult to measure because they are just one ragged hole not a lot bigger than bore diameter. Again, with retained energy being a primary consideration for making humane kills, I limit this rifle to 50 yard shots. So far it has only stretched to that distance once. By the same token, it has also harvested a whitetail literally at point blank range. In every case the round ball entered the ribcage and did not exit on the far side but rather ended up as a flat plate of lead lodged against the skin on the far side, having dumped its entire energy into the animal. Lethality with pure lead projectiles of this size and weight is phenomenal.
