[darkgael]

I just finished a 26 match set of indoor Bullseye match shooting.
A coupla things:
Bullseye shooting (also known as Conventional Pistol) normally is divided into .22 rimfire matches, Center Fire matches, .45 caliber matches. Ostensibly three guns; in reality, two guns as most shooters use their .45s for both the CF and .45 matches. The .45s are virtually all 1911s (though I had a friend who shot with a Colt SSA).
All shooting is done "one hand, unsupported". Two types of targets are used one for slow fire and the other for sustained fire (timed fire and rapid fire). All targets regardless of type or distance will appear to be essentially the same MOA in diameter.
The basic unit of Bullseye shooting is the National Match course - 30 shots: 10 shots slow fire, 10 shots timed fire, 10 shots rapid fire. A single set is called a 300 match. ALL Conventional Pistol matches are based on repetition of this simple set.
I am of an age where a red dot sight is a help. I have repeatedly tried irons but shoot better with the dot (Note: the NR for a 2700 match is held by Herschel Anderson since 1974 at 2680-159X out of a possible 2700-270X. It was shot with iron sights).
It is not accurate to assume that all red dots will obscure the bull. There are quite a few red dots that that offer dots of 3 MOA or less. Those are the ones that you want. I use a Bushnell TRS reflex sight with a 3 minute dot...very precise. Two MOA dots are not hard to find.
International Bullseye (ISU) uses different targets and does not allow red dot sights. Rapid fire pistol in the Olympics is one type of International bullseye.
Precision Pistol (more commonly called Free Pistol) is another.