ive been doin some research on some co wittness and im not realy giting it so i have a flat top upper im wanting to git a gas block with pica rail im wanting to run the gas block with rail and magpuls flip up sight and a primary arms micro dot with or with out removeable base? or a eotech! will someone point me n the right direction and school me on this thanks guyzz

Cowitnessing just means that you can use your iron sights through your optic.  For example, I use Troy BUIS with my EOTech.  If the EOTech ever dies, I can "cowitness" through the EOTech with my BUIS without having to take off my optic.

http://www.ar15.com/forums/topic.html?b=3&f=18&t=520028

It is generally not seen as good to mount the mbus to a gas block.  Look under "specs"

http://store.magpul.com/product/MAG245/45

Co-witnessing iron and red dot sights is a concept invented to justify the mistake of trying to use a standard A2 front sight with an optic.  The co-witnessers BS themselves that the A2 iron sight combined with some rear iron sitting in their vision through their optic or red dot is good.  It is a stupid concept.  The irons are always in the way.  Silliest is the RRA sight that raises the red dot, EOTech or whatever, above the iron sights.  Silly because it breaks your cheek weld on the buttstock to see the extra 3/8".

What you want is a high quality optic, Aimpoint, EOTech, or what ever AND fold down the hell-o out of the way iron sights.  ALL you want to see through the expensive optic is target and red dot.  Not the A2 front sight and a rear apperature.  If you break the optic, fold up the two iron sights and continue.

ok cool i got what i was looking for thanks again guyz

I use Aimpoint's with 1/3 co wit riser. ( like the middle one in pic) This is with the "stupid? " but ever reliable fixed front sight. I just flip up the rear if  need sights.  The front isn't even noticed.

If using cheap red dots you may have different point of impact when moving your head around and you will need your sights someday when you least expect it.

um ok I don't even notice my A2 front site thru my Eotech. Unless im looking for it.  Funny how it works just fine for me and the military and law enforcement and everyone that has it on this site. ya you can spend more money on a folding front site. Just don't bang it on anything.

1)  Very nice schematic of the ideas involved.  The center picture with the rear sight folded down out of view would demonstrate your point even better.  The front sight is only part of whats in the way.  The rear sight is the larger obstruction as in the center picture.  I have seen too many guys with the rear erected so they are instantly "ready."  They then permanently look through your left side picture which I, myself, and me think is daffy.

2)  You can get used to anything.  My point would be that you should not plan to clutter up the monster viewing area of an EOTech with iron sights.  If you manage to bust an EOTech beyond use, it is perfectly appropriate/desireable to have back up iron sights.  Having them folded down out of the way of your view unless actually needed is preferrable, I think.  Militaries and LEOs who were stuck with A2 front sights on a flattop receiver make do.

3)  Unless you have an ARMS lever on your optic, when the optic is busted beyond use and you cannot see through it to use the iron sights, do you have the hex/allen wrench needed in the buttstock kit to get the optic off the rifle?  If not, your BUIS is a waste anyhow.  Unless of course we are talking just dead batteries which is a user problem.

4)  The raised optics to see over the irons slow down sight picture acquisition.  An EOTech mounted directly on the receiver is eyeball perfect when you cheek hits the stock.

5)  Besides, that is why there are so many systems.  Everyone can find one they like.

Wondering why LaRue didn't get mentioned on this one.

www.laruetactical.com

If someone is looking through the iron sights and the red dot at the same time they are retarded. Some Military and LEOs are not only stuck with fixed front/fold rear fixed front/fixed rear some prefer it. I have folding front sights on some of my rifles but I have no problem with a fixed front. If you are planning on using your BUIS quickly after your optic goes down then you should be able to take it off quickly. New EoTechs are 1/3 lower co-witness from the factory now. If you like BUIS that (usually) aren't as durable...
Dustin

Wrong forum & Dupe.