I’m familiar with the military rifles. The 1776 rifle had 8 lands and grooves. The Poser Jaeger had 7, Ferguson Rifle had 8, A few of the American Rifles in Neumans’s book have 7 and 8. The Rappaforge rifled wall gun had 12 ! Holy Cow. French Infantry Rifles had 7. The model 1740 French Calvary Carbine was rifled at the breech and smooth at the top for about 4 inches, those had 7. I see your point though with the earlier single point rifling, broached rifling would be seen for a little while longer. I’ve seen some 6 groove American Long Rifles at the Valley Forge Exhibit and Rev War Museum in Phillie, but it’s possible that it was worn down or not in its original state.I though hand rifled barrels had an odd number of grooves as the shaft of the cutting tool needed support, and so if you had even numbers the shaft would ride inside with a groove beneath and and would not cut true. ???