Now you didn't say you had a budget you just said whats the best scope for a charger at 50 yards.
What do you expect us to do read your mind?
The best scope is the one that fits your budget and does what you need it to do. You are not going to get the best scope on the market for $200 not even $1500.
The BEST of anything is really subjective to a point of why even ask the questions.
If you would have said
What is the best scope for a ruger charger that will shot at 50 yards and below in the up to $200 catagory then you would have gotten a much better answer like.
I am going to then point you towards the Weaver 2.5-8x28mm
Might also want to take a look at the Bushnell Trophy XLT pistol scopes
If you can spend $300 then go with the Nikon Encore 2.5-8x28mm scope
with the BDC.
You were vague and left it wide open. Then you get upset about it.
Be specific and help comes easier and faster.