I inherited a bushmaster A2 M4. I am not familiar with rifles...hand gun guy...but have been reading this forum and responding on the general info site. Time to do something with this A2. Should I send it back to bushmaster and have an A3 upper put on it, or  should I just mount one of their bi-level rails that mounts to the handle? If the bi-level rail, what optic. I will probably be shooting under 200 yard targets. I just read an article in guns & ammo about the CRIMSOM TRACE laser that attached to the left side of an A2 and is operated by a switch mounted in a replacement grip. This way I would keep the A2 upper? Comments? Any help would be appreciated.

How far into this "project" do you want to go, e.g. $$$??

It sounds like you know your intended use of your new rifle, but is that it? Will you be using this weapon for any type of home/property defense? If so, maybe a "red-dot" optic is the way to go? How well are you trained with the iron sights? Become proficient with irons first and then make the move to optics.

There are quite a few guys who are successfully using the A2 carry handle mounted optic option. Compact ACOG's work vey well in that role. Aimpoints can work reliably when used with mounts such as the  ARMS 02

You can always swap out your A2 upper for an A3 flat-top, but then you'll find yourself needing a rear buis to go with your chosen optic.

I'm not saying $$$$ is no object, but generally it is no problem. Home defense would be in the cards...currently have a glock 23 by the bed. The bi-rail is similiar to what you suggested except it also drops down and extends over the hand guard.
Why are some optics mounted further forward, such as over the hand guard vs right on top of the upper. Thanks again for your help.

ok, you're thinking of the ARMS 39 mount

Location of mounting optics is dependent upon the need for "eye relief", magnified optics such as ACOG's need to be closer to the eye whereas optics such as Aimpoints/e0thingies tend to work better further out e.g mounted on a A3 flat-top above the chamber.

Yes sir, that is the mount I am considering. Would that work ok with an eotech?

Quoted: Yes sir, that is the mount I am considering. Would that work ok with an eotech?

I've shot an AR with the ARMS #39 and an Eotech. I think it worked great.