All the old frames around here that I have seen use the same wood for the pegs as for the frame -- old growth Longleaf Pine (heart pine. It is a great peg wood -- straight grained, tough, strong, stiff, and hard. Today's pine, though, is no more suitable for peg stock than closet rod is.
Also the way some of the pegs are deformed by the draw bore make me think they were driven fairly green.
I agree with Colin. Pegs are not suitable for tension connections and were rarely successfully used for such joints in the past.
Good luck with your pegs Andrew.
Cheers,
Gabel
