and am I ever confused.....

Here is what I have, Bushmaster A3 M4gery...

as of know, I have the carry handle on it, BUT I would like to mount an optic, BUT I dont what brand, or even what model would be best.

I plan on not shooting over 100 yards with this rifle, it is going to be my close range weapon.

Ok, so what brand and model optic should I be looking at?

Do I need a mount, in addtion to the flattop that my upper has? If so, what brand and model mount will I need, or which would be best?

Do I need a Back up sight? Or can I pass on it for now? If needed, what brand is recommended?

What about CO-WITNESS? I beleive this is where the dot on the optic, lines up with the pin in my front sight, correct?

As you can see, I have a few questions, any help here?

Gerenal recommendations for a CQB sight will be:

1.  Aimpoint M2 or ML2

2.  EOTech 510 or 550 Series


Both sights are quality instruments and generally fall into the same price range.  While I personally favor the EOTech, the more "battle minded" bretheren here will espouse the Aimpoint.

You'll want to research the two sight types and decide for yourself.

Hakko Tacpoint!!!!!  

Money available? Shooting paper and turtles or terrorists?

cheap...no drag

Hakko Bed-35--excellent holographic site with good battery life and excellent on the no eye strain scale. Mine seems to work fine placed directly on the flat top. 125-165.00

Tacpoint. cheap copy of higher priced red-dots. seems to work well but is sort of difficult to use mounted flush on the flat-top. Cheap riser or mount is available.
99-125.00
For magnification, several companies are making inexpensive scopes with and without lighted reticles.

I will let the Gucci shooter give the other options.

Ill stay away from the "type of optic" since there are so many flamers here.

As far as mounts. I have a ARMS 22M68 Mount with the throw lever and a ARMS 22M68 Cantilever forward extention. They can both be found at www.eaglefirearms.net for a good price. (great company too)

With that mount setup your red dot (aimpoint ML2 types or TacPoints) will co-witness perfectly on your flat top.

I know nothing of EOTechs or the hakko BED series.

1shott,
You said you need optics for a "weapon"? If this means shooting those nasty reactive targets that might shoot back, I would lean towards an EOTech or an Aimpoint.  And if you want to co-witness, you will also need a good BUIS (back up iron site) as you will remove your carry handle to mount your new optics.
My recomendation is an EOTech 552 RevF and an ARMS 40A. That is the same set up I use on my "Homeland Defense" rifle. The EOTech does not need an additional mount, so you can buy your optic and BUIS for the same as an Aimpoint and mount with no BUIS.