I thought the 42nd had Brit muskets at Ti. I know early on some Scottish light companies were using captures French muskets, but they probably were 1728 or maybe even a 1746.
As for the 1717 being PC, it's no less PC than French troops running around with 1763 from Pedersoli, and Brits running around with so called Short Land Pattern from Italy. A lot of reenactors I see at events still carry those guns, and they didn't even exist during the F&I, so don't let too many peoply bother you for using a gun that at least existed during the said time period!