When choosing iron sights for the SRC rifles, it is important to make sure you get the correct height front sight. Most manufacturers of rail mounted iron sights make two different heights for the front sight. With the SRC (and VEX rifles) you have to make sure you get a front sight that is for “same plane” sighting. In other words it has to be the same height as the rear sight that is mounted to the picatinny rail on the upper. Some confusion comes in here when you see a company that offers a “Gas block height detachable front sight”.
Right now we are one of the only manufacturers that make an AR15 in which the picatinny rail on the gas block is on the same plane as the upper receiver. Most company’s gas blocks have rails that are lower than the rail on the upper. Front sights for these rifles have to be made taller to make up this difference in height. So what happens if you mount one of these taller front sights on an SRC is your rifle will end up shooting way too low and you cannot move the front sight post down far enough to get the gun on target.
Below is approximately what the measurement is supposed to be for the front and rear sights. Note that is has to be the same or at least close to this measurement for both sights.
Rear sight, approximately 1.440″ from top of rail to aperture: 

Front sight, approximately 1.440″ from top of rail to top of front sight post:
