Good question. I have also seen the same combo bullet molds and wondered the same thing. I think 400 yards is quite a stretch, but then again they didn't have the same measuring devices we have today neither.
I once read an article in a Civil War era newspaper that advertised "Kentucky Rifles". The ad read something like; "those Kentucky rifles that can kill an abolitionist at 300 yards". Maybe there's some truth to the old long range claims after all ... ()
Optical sighting equipment, with lenses, is a 19th century innovation and were not all that useful until after the Civil War and many of these had poor light gathering and small field of view.
The picket bullet did not come into use until the 19th century. To use these efficiently, IE any accuracy, requires equipment you are not going to see in any Rev-War dig. Nor do I know of any elongated bullets surfacing before perhaps the Mexican War or possibly Alamo era fights.
I don't see any reason to doubt the word of a skilled rifleman and military officer who was familiar with the area having passed over it several times stating that the range was 400 yards.
I don't see a problem recreating the shot either if a doubter has the time and place and a rifle with an accurate load. Shooting accurately past 120-150 requires more care in loading BTW.
Morgan's riflemen killed Frazer and wounded another high ranking officer officer at 300 yards at Saratoga.
A friend could hit a 30" gong at 500+ with his 54 flintlock once an aiming point was found.
The difference is that we don't shoot at 400 with a RB gun very often, though hitting 300 yard man silhouettes is not that tough unless the wind is high.
If using one for WAR for REAL then the rifleman might well have some experience at these distances and if he knew where to hold putting a ball within a few feet of the target is not going to be that tough. So Hanger's account is certainly believable.
If one never shoots past 50 yards a 150 yard shot can be tough. But if one shoots to this distance now and then 150 is actually an easy shot on a human sized target and can be done with small bore 36-40 caliber rifles.
In actual testing at 200 my 54 will hit a target the size of a man's head 3-4 shots out of 5.
Dan