Hamish - That is Not an optimal .30-40 load and I am not recommending it. There are better propellants for the Krag with the 168 grain Spitzer.

(It is convenient for me, because I have a lot of WW-748 propellant and 168 grain Match Kings. It's a decent load - I believe to be safe).

I do recommend trying weak 'Readers' (1X or 1&1/2X), that have 'safety lenses', to try and see fine sights more clearly.

FWIW - A few years back, I had cataract surgery and have close to 20/20 distant vision, but, need 2X Readers for reading. When I use 1X Readers, as shooting glasses, the sights are clear and the 'Bull' is only a bit blurred.