The S510k is probably the pinnacle of the S400/410/510 gun range. Gone is the regular bolt action and in its place is a side lever that is slick and quick to operate; it is designed to be so smooth. A gun that a shooter can cock and load the next pellet whilst never removing their eye from the scope. Also, the S510 comes with a bull barrel that is aesthetically very pleasing and is devastatingly accurate, as well as incredibly quiet. The S510 is based on S410 technology. The S410 is the multi-shot derivation of the S400. It borrows all of the refinement and development from the s400 series, but it also adds a 10 shot magazine system that makes the s410 extremely popular with hunters and plinkers alike. In classic form, it has a great shot count, a superb adjustable trigger and is both well-proportioned and elegant.