I'm new to the board and will be building my rifle in the very near future.  The rifle will be used for patrol and training.  I would like to put a red dot or electronic sight on it also.  Does anyone have any experience or opinion as to which style of receiver/mount combination is best.  I am considering flat top upper with an ARMS #40 rear and mounting the red dot to the receiver or is it better to keep the A2 configuration/sights and mount the red dot on a mount like the ARMS #39A2Plus.

Which option will be the most flexible, stable, cost effective and user friendly.  I would also like to keep the optic sight in line with the iron sights as much as possible.

Thanks for any help.
Sarge

BTW, I'm going to be using RRA for both the upper and lower.

Lowest cost will be Aimpoint on a gooseneck mount on an A2 upper.  Most flexable (and expensive) will be Aimpoint with ARMS 40 rear sight and Aimpoint on a cantalevered mount over the delta ring.

I have an uncle name Sam that has researched your question to no end and have picked up the two systems as DevL has described.

You need a set of iron sights at the ready at all times for a duty weapon.