Hi 8x68,
An aperachure or "peep" sight, relatively close to your eye is, if not intended to be blurry, certainly is of little to no consequence that it's blurry.
That front sight is the one that needs to appear "crisp".
And the target should be also slightly blurry, (easier said than done in a charge, no doubt).
My eyes are to the point where the typical tiny notch in "normal" rear sights is very difficult to impossible for me to see in poor light.
But a large aperature, sometimes called a "ghost ring", combined with a white front sight, gives me a usable sight picture, even in not the best light conditions.
Admittedly, a rifle scope is best for me now (My eyes are 64 years old these days), but I can still shoot straight with the above mentioned, over-sized peep sight.
Another rear sight worth mentioning is the wide, very shallow "V" or "express type.
With one of these and a large white front bead, when the rifle is regulated for a "6:O'Clock hold" at - name your distance within reason - with this arrangement, I can shoot pretty well, even with my antique eyes.
So, if for some reason you do not want a scope on your rifle, (personally I don't like them on doubles), the "ghost ring" or the "express sight" could possibly work for you.
Cheers,
Velo Dog.