Having astigmatism I've given up on red dots. They usually starburst for me, making accurate shots past 75 yards near impossible. I had the chance to try out a 6 moa C-More red dot on a 9mm AR SBR yesterday. We were shooting outside with overcast skies. Brightness was approximately set to 7 of 9.  There was no distortion of the dot or starburst present. This was an unexpected result for me. I've had no luck with Aimpoint, EOTech, or Primary Arms red dots. The model used:

https://cmore.com/Item/ATRWS

They come in 2, 4, 6, 8, 12, and 16 moa dots. I'd like to try out a 2 moa dot for longer range shooting. Hopefully I'll have luck with the smaller dot as well. 

I placed an order for the 4moa aluminum railway last night.  It will be used on a Gmr-15 but looks like it won't ship for another two weeks so no range report for a while. From all the reviews I've read it seems like it's great for competitions like steel and uspsa which is what my usage will be.  I really liked how open the sight was compared to other red dots I've tried and it's pretty reasonably priced.  Hope I like it! 

I took my Burris FF3 off my model41 ,   with astigmatism it doesn't really help.    I do just as good or better with iron sights.   I wonder how a pistol scope would work. 

Have you tried one with a Green dot?