I bought this tranter lever opening Jeffery Rook Rifle 297/300 with a 27" barrel that had been resleeved with a parker hale barrel to 22LR. The firing pin had been moved up to make sure it hit the rim of the 22LR. After being off 5 inches high and to the left. After leaving it with mialls for 4 weeks with Eley EPS 22LR target ammo they had it shooting 35mm high at 35m for about a 50m zero with the 50m flip sight. I suspect it was never altered from the 550fps the old rook round was doing.
Its a great little rifle that doesn't bust your shoulder.

https://youtu.be/DBeFWrkxQ9E