For whatever it's worth...around 1780 the British Ordnance Department did an exhaustive study comparing one of their Pattern 1776 rifles with a captured "New York Rifle". Of course, we don't actually know what the rifle was, it may just have been taken in New York but it's interesting just the same. The report was never published and exists today as a MS ... in fact, the copy I was sent photocopies of is believed to be George III's. It's actually quite boring unless you are into serious ballistic studies.