Hello, I just purchased a Eotech scope. I am going to mount it on my Colt A3 version. If I mount it on the flat top I need to have back up sights. The arms #40 seem like a great choice for the rear. What about the front sight? Do most people leave the stock front sight on or put on a flip up sight? If you install a flip up sight do you need to put in a front gas block? If so which is the best way to go for a front gas block? What is the best way to go for a front flip up sight? Thanks

The #40 is a good sight IMO. If you wanted to use a flip-up front site you would need to put on a gas block that would allow the mounting of a front sight. I would suggest that you just keep the front sight and add a flip up rear. At leas that is what I did. [:D]
[img]http://photos.ar15.com/WS_Content/ImageGallery/IG_LoadImage.asp?iImageUnq=10916[/img]

I agree with VA-gunnut.  Also, I got a MAD as my rear sight, and it seems to work well.

[img]http://www.burnerblog.com/gallery/albums/userpics/10001/normal_2003-3%20006.jpg[/img]

Here's a picture of my sight picture through the ML2, MAD in the DOWN position:

[img]http://www.burnerblog.com/gallery/albums/userpics/10001/normal_2003-3-1%20010.jpg[/img]

Here's what it looks like THROUGH the MAD:

[img]http://www.burnerblog.com/gallery/albums/userpics/10001/normal_2003-3-1%20011%7E0.jpg[/img]

Here's what it looks like OVER the MAD, with the MAD in the UP position:

[img]http://www.burnerblog.com/gallery/albums/userpics/10001/normal_2003-3-1%20014.jpg[/img]

And finally, a closer view of the MAD, ML2, #22M68 w/spacer on my M4:

[img]http://www.burnerblog.com/gallery/albums/userpics/10001/normal_2003-3-1%20016.jpg[/img]

I hope that this helps!

I use an ARMS 40 and the stock front sight with my Eo-Tech.  It works well and I don't see any reason to go to a flip-up front sight.

If you decide you want a flip-up front sight, I have tried the Bushmaster and it works well.

The disadvantage of a fixed front sight is it obscures your field of vision the further out your target is. The advantage of a fixed front sight is it makes the transition to your back up iron sights much faster. Thats the long and short of it. Personally I use a fixed front sight. But its a personal call.
PAT

The only front sight you should consider other than the fixed sight is a PRI front sight.

I had to look hard at Edge767's first picture.  It seems we have almost the same rifle...and carpet!  [:D]

I like the fixed front sight.  If I have an optic failure, I don’t want the added time of flipping up the front sight.  Aimpoint and Eotech type sights are designed to co-witness irons.