They had their Ferguson rifles they brought in during the Revolutionary War as a counter to the American weapons. They were, in fact, military-grade weapons to the American ‘sporter’ version: they were heavier, threw a heavier round, and far sturdier and easy to repair. All of which was laudable, and they thought that they had the superior rifle.
The problem was that while their rifle didn’t break as much and was more rugged, it required a base of skill they basically didn’t have in England (for a long time after 1815, too) and the more delicate American rifles generally outranged it by quite a large margin. Which some would argue is rather the whole point of rifles... especially ones that were employed in this role.
Not to mention that the American long rifle was fairly easily replaced when it did break (due to its relatively simplicity of design) whereas the Ferguson generally required the repair expertise of a craftsman in a large city if not in England itself.