HappyHunter: Yup, those sights are not good on old eyes. The front bead sight is tough enough to pick up, but it is even worse to try and center it in that modified buckhorn Winchester uses for a rear sight.
I would try a couple of tricks: (1) I would pull the sight blade out of the rear sight so you have more of an original buckhorn sight, which is pretty open and makes it easier to both see your target as well as the front sight. If that works for you you will probably have to get another front sight blade (I use a blade front sight from Brownells with a white stripe in the center - very easy to pick up quickly) to get your rifle to print where you want it to at 100 yds. Or, (2) if that doesn't work for you, try an aperature sights/peep sight/ghost ring for the rear sight and go with a blade front sight - those seem to be the best combination of sights for many folk.
Check out Brownells for those sights, or find the Ashley Ghost Ring sights on the net - prolly under Ashley - and then you can see what I mean. If you have had any military experience since WWI, then you will have used the military rear peep sight and the ghost rings work the same way. HTH. Mikey.