Modern Gunsmithing by Howe has a rundown of the work involved. Don't recall offhand which volume it is in.

I've seen them by G&H, Neidner, Sedgley, and Hart. The Neidner appears to have been converted by G&H. If not, then they sure did a good job of copying the G&H conversion. They are not Winchester magazine box's.

I always thought these made a heavy rifle for a Hornet. The Hart Rifle has had the barrel recontoured and is a much better walking varmint rifle.

John