Ok , ill drop my 2 cents as well . The photos are a little deceiving so its real hard to tell but here is what Im looking at .
The ramrod as it enters the entry is way bigger then what we see as it exists the entry .
While this may have a tapered ramrod . That doesn’t explain IMO why this size is so drastically smaller in a short distance . Im thinking what does explain this is that the RR channel that we are seeing is just the very edge where its broke through . If we look at the trigger guard we can also see that its broke through as part of the forward final is actually under the wood . There also appears to be large chips in the stock up around the entry final as well as all along the channel that we see .
These would not be there if this was the original condition of the rifle . What we would see is a even line on both sides going all the way back to the front final on the trigger guard
Now , why would this happen . Well simply put , the belly of original rifles are notoriously known to be very thin . Its part of how they get the very thin lines . A lot of times this area is in fact no more then 1/8 inch thick . If you have ever seen a brass belly plate on a rifle . Know that its not just there for decoration . Its there to cover and protect the RR channel . It was also done as a period type repair for the very reason your seeing .. If built correctly there also should be a slight taper to the belly of the stock . IE the stock is thicker at the lock mortise area and tapers towards the entry . This we can see by the amount of RR that is showing back at the TG
Today a lot of builders , especially those building from pre-carves often leave way to much wood in the belly . Doing so creates a thicker wall for the RR channel . But at the same time also makes for a less slime line .
Now as for the channel not being strait down the belly but canted off to the side plate or off hand side .
This is also common . What this does is keep the main spring inletting from breaking through into the RR channel . It also serves to force the RR to bend as it goes into the entry and helps hold the RR in place .
The other thing it does is allow for the RR to extend all the way back just past the breech , while missing the TG pin lug , which would break through the channel if the channel was drilled strait down the center line .
So how did this rifle end up with like this . Well we can only speculate. Someone may have tried to refinish it at one time and in adversity sanded through into the channel or made the channel so thin that it broke out .
OR
Think on this . If this is truly a rifle that saw service at King Mountain , IE close quarters combat , IMO I would expect to see this kind of damage regardless of the side the rifleman was on .
If it was held by the over the mountain men, these men were advancing up hill and firing from cover . So they would have been running from cover to cover . Probably firing from both standing and prone positions . So I would think the rifle would have been landing sharply on its belly a lot .
Once these men got in close they would have not only confronted other rifleman but also Fergusson’s regulars . Which by that time would have fixed their bayonets. In which case the belly of the rifle would also have seen heavy blows as part of parrying a bayonet thrust
If it had been in the hands of a Tory rifleman then I think we could also see this type of damage in this location as these men would also have been firing from cover . Thus the rifle would again have been dropped on its belly heavly in the cause of the battle . Remember these men were also firing down hill . This meant that in order to be able to bring a bead on an advancing person , the belly of the gun would have been the main contact point , time and time again .
If you have a long rifle , you can test this for yourself by laying your rifle across a log , rock or any suitable rest . Now try and point the rifle down hill . The only way you can do that and still remain somewhat behind cover , is to extend the muzzle well past the what ever its resting on . IE you end up with it resting somewhere behind the entry , back to the trigger guard depending on who steep of a down hill incline your trying to fire to . Anything forward of that and you will end up presenting a very good target for any reasonable marksmen . Lets not forget Ferguson’s men were not facing just marksmen but sharp shooters on mass . In other words men whos very lives depended on their ability to shoot and shoot accurately. To exaggerate some , many could probably take the nuts of a Nat at 100 yards .
So regardless of what side the rifle was on the belly should IMO have seen repeated blows that would have fractured , if not broke out the RR channel . Over time those pieces would have fallen away .
If it was owned by someone with little money, as many of the over the mountain men were . There probably wasn’t much need for it to have a belly plate put on as its still functional . Once the TG fell through then the rifle probably would have been set aside or delegated to home defense as a spare rifle that was still usable but not in top working order .
Now if it was left on the mountain, IMO it wasn’t there long OR someone has again tried to refinish it as it doesn’t IMO from what we can see , show signs of long term exposure to the elements