fiber optic red spot
"RV":
Please excuse my diversion.
However, I put a fiber optic front sight and an aperature rear sight on my four inch barrel GP100.
Certainly not a Red Dot, but it is picked up by my eyesight readily, the aperature does not obscure the sight picture as much as a notch type, and
for less money, less bulk, and perhaps more reliability I would recommend you consider that alternative.
I have not used the Red Dot, as you asked for, nor do I think the mechanical set up I mentioned would give you the longer range enhancement that
Hardluk1 describes.
For hunting, or other?