I did a Rappahannock Forge musket from Dave's pattern. When the 2nd Continental Congress wrote "specifications" for muskets to be supplied to the Continental Army, they were very vague, to say the least. About the only guideline utilized, were that the arms be "in the manner of" or "in like appearance to", the British muskets. It gives you a lot of lee way, and there were a lot of variations.
Ed