The legal firearm inside an Echelon weighs 3 oz (85 g) and measures 4.3 x 1.9 in (10.9 x 4.8 cm). Springfield Armory is now selling that piece on its own, which means you can buy the serialized heart of the pistol and build everything around it yourself. The Central Operating Group is the chassis that holds the fire control components, and it is the part that carries the serial number. Everything else- the grip module, the slide assembly, the barrel, the sights, the magazines- is just parts. Buy the COG and you choose the rest, from Springfield's own catalogue or from the growing aftermarket built around the platform. The OEM options already cover a lot of ground. Grip modules come in Compact, Full-Size with Compact Dust Cover (sized for a 4.0" slide assembly) and Full-Size. Slide assemblies come in 4.0" or 4.5", in standard or integrally compensated form, which means the compensated slides from the recently launched Echelon Pro Comp line are on the menu for anyone building from scratch. This is the approach I find genuinely useful rather than just clever. Buying a complete pistol and then replacing the grip module, the slide and the barrel to get what you wanted leaves you with a box of expensive parts you will never use. Starting from the serialized core and specifying forward means you pay once for the configuration you actually want. It also means a single serial number can become a compact carry gun, a full-size range pistol and a compensated competition gun over its life, without ever being a different firearm on paper. In construction, the COG is stainless steel throughout, with critical trigger components machined from tool steel. Surfaces are precision polished and coated to reduce friction, which Springfield says gives smooth take-up and a predictable break. Worth noting separately: the COG uses a second sear design intended to help prevent unintentional discharge if the pistol is dropped. Steve Kramer, Vice President of Marketing for Springfield Armory, frames it as the logical conclusion of a platform that was modular from the start, giving shooters the means to craft a pistol configured exactly for their needs. One practical note before anyone gets excited. Because the COG is the serialized component, buying one is buying a firearm, and it transfers through an FFL like any other. Springfield Armory Echelon Central Operating Group specifications:Part number: EC9900-RET, UPC 706397012373Caliber: 9mmConstruction: stainless steel, tool steel trigger componentsSecond sear design for drop safetyPrecision-polished and coated friction surfacesColour: blackWeight: 3 oz (85 g)Length: 4.3 in (10.9 cm)Height: 1.9 in (4.8 cm)Frame compatibility: Echelon compatible grip modulesMagazines: Echelon patternGrip module options: Compact, Full-Size with Compact Dust Cover, Full-SizeSlide options: 4.0" or 4.5", standard or integrally compensatedSerialized component, FFL transfer requiredMSRP: $295Is the aftermarket deep enough yet for Echelon-based builds?If this post has you ready to hit the range, head over to gunranges.com - a free directory to help you find shooting ranges near you, wherever you are in the United States.