Thats a 512 eotech and I picked it up on the board here for 300 and change
The G3 upper has a 1 in 7 twist barrel and the RH3 upper is 1 in 9
you sir are correctUhhh.....No. That would be the "N" cell model, the 511. 512 is AA battery.
TDC
...Going to look into a Larue ACOG mount and maybe a 9" rail and VFG down the road.
Since I am keeping the A2 FSB I might look into a rail with a cutout for it and a longer rail, who knows.