I have just taken a look at photos of the different actions.

The recoil lug on the 1891 receivers is much further back than on the 1893/1895 receivers. Unless Claven 2 knows how to do this, this looks like the problem that invalidates the whole idea. The recoil lug bears (I think) on an inlet plate (on later models, the recoil bolt) that has to be very well fitted AND have strong material behind.

Sorry, I don't think it's feasible.

Patrick