what can i expect from a bsa red dot sight as far as accuracy? i was thinking of putting one my car 16" carbine. any opinions on it?

Save your money and buy an EOTech.  No comparison.

EOTech is better.
ACOG is even better.

Does that mean that a BSA doesn't work ?

I think that there's a middle ground to be had. If you put a BSA on your AR, I would not trust my life to it. That being said, a Tasco is exactly what I have on a detachable riser bar on my AR most of the time. Why ? I can't afford an EOTech right now, and for PLINKING, it works just fine. Heck, I'd be willing to bet that if I had my rifle next to me when a bad guy walks through the front door, that I'd be able to assist him to the afterlife fairly easily. Would I expect the same scope to work if I was outside for an extended period of time, through rain, mud and other crap? I don't think so.

So yes, a $300 scope is better than a $50 scope, but not everyone needs the $300 scope. I've had a lot of fun shooting with mine FWIW.

I have a BSA red dot on my AK-47.  I think it is a piece of shit.  Depending on how I look though the thing my shots are very unreliable.  I am pretty sure it is the red dot and not the gun.  I am going to put a different scope on the AK sometime just to make sure.

With that being said I would stay away from one.