I had that trouble with my old eyes too, until I had cataract surgery. Now I can use my open sights just fine on my levers and smoke poles. I'm 76 years young too. Maybe get your eyes checked.There could be help for you.
I cast and size all my own slugs and like you, I size to .460 on my bullets for my 45-70 Guide Gun. In fact, I size all my bullets for whatever caliber I am casting for at .002" over bore dia. With my muzzy's though,I just find the factory roundball that shoots the best out of them. I have several muzzleloaders but the Lyman Great Plains rifles I built from kits, I like the best and they shoot well. I don't shoot the front stuffers that much so I see no need to melt my pure lead for them. By the way, I have not had any trouble finding powder. It seems it has been being made more now.
I cast and size all my own slugs and like you, I size to .460 on my bullets for my 45-70 Guide Gun. In fact, I size all my bullets for whatever caliber I am casting for at .002" over bore dia. With my muzzy's though,I just find the factory roundball that shoots the best out of them. I have several muzzleloaders but the Lyman Great Plains rifles I built from kits, I like the best and they shoot well. I don't shoot the front stuffers that much so I see no need to melt my pure lead for them. By the way, I have not had any trouble finding powder. It seems it has been being made more now.