Some, not all rifles will throw the first shot. Actually if you want to get real, they throw the second shot. Its the first shot that is accurate. For that reason some people sight in on their first shot and then learn where their second shot will go.
BUT.. others will fowl the barrel before they hunt. They drop about 30 grains of powder, down the bore and set it off. Then swab the bore and load. Now their second shot is their first shot. The problem with that is they basically have to clean the rifle each night or take the chance of what the fowling will do to the barrel. That is one of the advantages of this new BlackHorn powder. You can shoot all day and never worry about what the powder will do in the barrel. Also depending on where you live, such powders as Triple Seven can be left in the bore for extended periods of time.
Its all a matter of consistency. To have the best accuracy with a muzzleloader you want consistency shot to shot. So if you shoot on a bone clean barrel, you really can not expect the next shot on a dirty barrel to be the same. Now some rifles will to be that far off. So test your rifles.
One thing I have been experimenting with is Montana Bore Conditioner. I am hoping that it will bring the first shot in with the second shot. I am still testing on all of that.