now to muddy the waters... We may be off base with our help.
This is copied from the Lyman Q/A pages .
In some cases it seems you do need to change the tang. They are talking about the "Hunter barrel " and Great plains Rifle l here, with the fast twist.
Lyman Products Your Primary Source for Reloading EquipmentQ: I have a Great Plains Rifle. Can I just purchase the Hunter barrel to convert it to shooting conical bullets?
A: Yes, the stocks are the same.
The new barrel will come with a matched tang which will need to replace your existing tang on the rifle. I did have to shorten a rib on a barrel to make it fit diferent model Investarms stocks one time. , but never a tang.