Welcome!!! Your rifle came without any sights from what I've read. So the big decisions should start with sights
Optics come in two major groups, red dots and telescopic sights. Red dots are faster to acquire targets, allow the use of both eyes and are good out to 200 yards or more with a magnifier. They are ideal in many ways for a rifle with a 16 inch carbine barrel. If you go the red dot route you should add iron sights to co-witnedd with the red dot.
The military uses the Trijicon ACOG with four power fixed magnification and a reticle calibrated to military ammunition. They are very durable and are expensive.
The modern telescopic sight many civilians use is a variable power scope with or without a lighted reticle. The biggest mistake on scopes is usually too much magnification.
SIG is very new to manufacturing sights. Their telescopic sights are built like tanks and are therefore very heavy for what they do. IMO, the bugs are not yet out of SIG's scopes. High end scopes are usually adjustable in .1 MRAD or .25 MOA, i.e., about a third of an inch or a quarter of an inch at 100 yards. SIG went with .2 MRAD and .5 MOA on their tactical 1-6x24 tactical scopes which is ok for short shots but is not good at long distances. (I own several SIG optics.)
Good brands of red dots from most expensive downward are Aimpoint, Trijicon and Vortex. Telescopic sight brands of quality are too numerous to list, but always look at Leupold, Vortex, Burris and Bushnell to name a few. Quality is usually proportional to price.
Bill
