just put a b square mount on my ruger Mk2 now i am wonder if i should put a red dot or Bsa pistol scope on it.Open to suggestions

Here's what I found. I've shot the ruger mark II with both and find that I am much steadier with the red dot than the scope, especially offhand. Mine ended up with an aimpoint 5000 with the two minute dot and is so accurate set up that way it was scary.

With a scope every bit of shake is seen thru the lens and that makes it harder for me to shoot. I've no doubt that the scope makes for a very accurate weapon, but at any magnification shooting without a rest was much harder for me than the red dot.

This is strictly Opinion.I would go with the Red Dot sight.
Frank

Have had both - a Tasco PDP5 and a BSA 2.5x20 pistol scope. The MkII is the ss Government 6" bbl'd model. The reddot gave a better field of view and didn't weigh as much as the scope. The scope seemed to define the target better. Hobson's choice.

I'd suggest a third option. I have a Dr Optic on my .357 and a similar but cheaper Tasco Optima 2000 on an S&W 22A. They are both much more accurate than I can shoot with open sights. Those are "tubeless" red dot sights. They weigh only about two ounces and mounted in place of the original rear sight they are hardly any bulkeir than many adjustable rear sights. They have unlimited eye relief and as they are non-magnifying and have no tube the field of view is aslo unlimited. I understand that Burris now has one called the "fast sight" I think but being made by Burris it should be much better quality than the Tasco but less expensive than the Dr Optic. I plan to put one on my AMT automagII as soon as I can find one. I think the suggested retail is about $220 but like most gun items will probably sell for less.