Not sure where to put this, but here it is.
: One of the most important aspect of shooting (chunk) prone, is not to try to steer the gun with your cheek or the trigger hand in the slightest. Steering with cheek or trigger hand will throw shots. The only part of your body that is used to move the gun is the 'gun' or 'butt' hand, which steers the rear of the stock for windage and up and elevation while holding it snugly against your shoulder. The rest of your body must move with the gun as it is adjusted and not be trying push it around. More cheek pressure on the next than on the previous ones and you've a pulled shot. Of course, flinters must be held absolutely stationary until after the gun has discharged and the ball is on it's way. Shooting muzzleloaders is very much like shooting small bore, except due to ignition times, the time from primary ignition to discharge is even slower. Couple that to a long barrel and man, are we way behind the 8 ball. A cant block helps keep the gun perfectly horizontal, but pressure against it will cause off shots as well. The gun must be neutral on the rest, with no pressure to either side not excessive up and down.