Most popular rifles have evolved throughout their service life. Lee-Metford action of 1888 lasted into the 1950s, changing in that time its stock shape, its sights, the method of loading, the safety, the trigger mechanism and even the type of rifling. AK47 evolved from a 7.62mm milled rifle into a 5.45mm stamped AK12 with hundred of minor changes and improvements.
Crude in its initial form, the AK platform has incorporated features from other Western and Asian designs to make it a rather more effective and ergonomic weapon. AR15 and the derivative M16 of the 1950s aren’t very similar to the modern AR family rifles on the outside, though the manual of arms and the action remain substantially the same.
Changes to the commercial arms are as common but often harder to track. The civilian market seldom designates changes in the thorough Mark/Mod. manner of the military. Earlier versions are almost never updated the way military arms are. The A model of Keltec SU16 was the oldest and most humble example of the series, dating back to 2000. The sole long-barreled variant without threaded muzzle, it was superseded by the more glamorous shorter rifles with more options. Certain features of the SU16A, such as the plastic front sight assembly, were viewed as typical of the entry level rifles. It gained a considerable popularity anyway, especially with people who live in restrictive states like California but want a viable defensive carbine. I paid little attention to it, focusing more on the E variant, with threaded muzzle, a pistol grip and a collapsible stock.
Even working directly with Keltec and seeing most of their revisions first hand, I was recently taken by surprise by the evolution of the SU16A. The newest revision of the A variant has an entirely metal front sight assembly. It is available in a variety of durable Ceracoat colors, which both make it cooler in direct sunlight and easier to camouflage. The 18.5″ barrel gives 150-200fps higher velocity than 16″ carbines and a whopping 23.5″ sight radius, nearly 30% longer than an AR15 with the same barrel length. The sight radius is 60% longer than the standard 16″ barreled AK. While Californians cannot legally buy it with 30-round magazines, SU16 can carry two 10-rounders in the stock ready for rapid reloading, giving the total of the same 30 shots if necessary. The whole rifle folds in half at the receiver, making discreet transportation possible. The forend halves even unlock form each other, forming a simple but useful bipod.
The design is optimized for hunting and provides respectable slow-fire accuracy, generally 2MOA with ball ammunition. It’s not designed for sustained fire but can handle 50-60 rounds before becoming uncomfortably warm. Fortunately, few self-defense events require more than half a dozen rifle shots in a row.