Folks,
The belly box held 9 to 18 rounds. The hip box held 18+ cartridges as the AWI progressed.
As for turning the head when firing, turning only means you get burnt on the back of the head instead of the cheek. IF it was a reaction to a worn touch hole it is more likely a soldier would duck his left cheak to his left shoulder, and take the burn on his hat not his body. The leather neck stock wasn't used until the 19th century, and the soldiers could move their heads... the neck stock was merely thought to provide a neat appearance, and later somebody thought a thick, leather stock might help against saber cuts from Napoleonic cavalry...
Turning the heads may have been more an exercise for the soldiers in tight ranks looking down the line to the right so they could see the Serjeant or Officer giving the fire command.. and perhaps to see either the officer's sword come down, or the serjeant's halberd move thus indicating FIRE!... imagine that after several rounds while being surrounded by 50-100 men in one company firing 150+ grains of powder in each musket per shot... the soldiers probably couldn't hear.
By the AWI the British Infanty in North America fought at "open order" standing one arm's length apart and in two ranks..., nobody is being hit with the spray from the musket touch hole on a regular basis, and the men are too spread out to turn their heads to see people motioning to fire, so they had to hear the fire command. Firing at marks was important as was maintaining the line when attacking with bayonets at open order. See With Zeal and With Bayonets Only by Matthew Spring.
Light infantry was created for the F&I and then created again for the AWI. The light infantry were sometimes formed into "Marksmen" companies, and were issued loose ball and powder to make their own cartridges for accuracy. They were expected to be able to consistantly hit a 2'wide by 6' high target at 90 yards, offhand, to be considered a marksman. A full round hole was a "hit" anywhere on the target board counted... it was hit or miss, and if you consider it, if you put the full diameter of a musket ball through somebody's body part that pretty much would take them out of the fight, whether it was an ankle, wrist, or someplace else, no?
Just like rifles, the marksman of the British army had to either stop and swab the bore at some point in the battle, or had to start using standard ammunition not made to "fit" his musket's bore as the fouling increased.
The British employed rifles in the F&I, Pontiac's Rebellion, and the AWI. The Ordinance Rifle Pattern 1776 is a famous example, and Henry Bouquet mentions procuring rifles in his action against the Ottawas during Pontiac's rebellion (iirc).
As for the accuracy of the reproduction Bess.. you should be able to put the ball in the vitals of a deer standing broadside to you at 50 yards. You may be hampered by the very large bayonet lug that is used as a front sight post. Some folks report very good success by making a paper cartridge that fits inside the bore, and holds the musket ball in the same position, rather than using a patched ball where the patching material creates inconsistant folds from shot to shot.
I have seen fellows make a rear sight for hunting purposes that affixes to the musket by using a tang bolt. I have also seen fellows with a very wide bayonet lug make a \/ notch in the top giving them a tighter point of reference, as well as one clever fellow who took a thin jewlers saw, after using a pen to mark his bayonet lug where it shot true, he created a slot in the lug, and then added a thin piece of German silver. He smoothed this down to the top of the lug, and then browned the lug a bit...so the steel was dark but the silver stayed bright... so he ended up with a very visible, verticle | line as an aiming point, and it also didn't interfere with his using his bayonet at historic events.
LD