I don't know about the British military in the AWI, but others are recorded as having loaded loose ball, not always cartridges. In the F&I war Rogers' Rangers did that.
AN HISTORICAL JOURNAL OF THE CAMPAIGNS IN NORTH AMERICA, 1757-1760 by Captain John Knox:
"A body of rangers, under the command of Captain Rogers, who arrived with the other troops from the southward, march out every day to scour the country;.... a bullock's horn full of powder hangs under their right arm by a belt from the left shoulder; and a leathern, or seal's skin bag, buckled round their waist, which hangs down before, contains bullets, and a smaller shot of the size of full green peas: six or seven of which, with a ball they generally load;"
Spence
AN HISTORICAL JOURNAL OF THE CAMPAIGNS IN NORTH AMERICA, 1757-1760 by Captain John Knox:
"A body of rangers, under the command of Captain Rogers, who arrived with the other troops from the southward, march out every day to scour the country;.... a bullock's horn full of powder hangs under their right arm by a belt from the left shoulder; and a leathern, or seal's skin bag, buckled round their waist, which hangs down before, contains bullets, and a smaller shot of the size of full green peas: six or seven of which, with a ball they generally load;"
Spence