The FN SCAR series of short-stroke, gas piston-operated rifles have the distinction of being the semi-auto version of the very rifles carried by USSOCOM. The SCAR 16S and 17S, chambered in 5.56x45mm and 7.62x51mm, respectively, feature cold hammer-forged, chrome-lined, MIL-SPEC, free-floating barrels. Fully ambidextrous, the controls adapt to any shooter in any shooting position. The polymer stock is telescoping, fully adjustable for length of pull and comb height, and folds to the side for storage. The receiver incorporates a MIL-STD 1913 optical rail. Three rails (at 3-, 6-, and 9-o'clock) mounted forward of the magazine well permit the mounting of accessory optics, lights, and lasers. Both models incorporate a gas regulator, enabling the shooter to adjust gas flow for optimal operation when firing with a suppressor. Both models are available in matte black and FDE.

For the operator, the primary difference between short-stroke, gas piston-operation and that of direct gas-impingement is that, in the case of the former, the bolt and chamber are not exposed to heat and soot carried by the expanding gases accompanying each fired round. This "cleaner" operation may improve long-term reliability. Whether there is a difference in accuracy potential between rifles operating with one system or the other is a matter of debate; there are advocates on both sides of the discussion.

It is worth noting that the SCAR series shares something in common with: the M14 series of rifles (fielded by generations of military personnel and currently in service with the U.S. military as a semi-automatic designated marksman platform); the M1 Garand; the FN FAL; the IWI Tavor; and the SKS45 and AK-47, and variants thereof: all are piston-driven. Enthusiasts of one or more of these platforms know that all are widely-considered to be extremely reliable, even in adverse conditions. Undoubtedly, this is a major factor contributing to the wide-scale use of these platforms by military forces around the world.