I really could not say. I do not own a White Mountain Carbine [&o] While the barrel is not round for the part that lays in the stock, the barrel then turns round on the barrel after it leaves the stock part.

I can tell you I took my barrel that would fit a White Mountain Carbine and tried to install it right now.. into the Pennsylvania Hunter and white it fits the stock, it does not match in the wedge lock area... So I will guess that they are not the same..

Hope this helped.