Tubb Lightweight Flatwire Buffer Spring

The Tubb Lightweight Flatwire Buffer Spring is David Tubb's lighter-than-mil-spec AR action spring, wound from flatwire stock instead of round wire. Superior Shooting Systems markets it for platforms running low pressure loads such as 300 Blackout and 300 Whisper, where a standard buffer spring can over-resist a softer impulse and cause short-stroking or sluggish cycling. The flatwire construction packs more material into the same coil envelope, which lets Tubb reduce spring rate while keeping the spring stacking smoothly inside a carbine receiver extension.

Where this spring earns its place in a build is rate-of-fire tuning, not raw power. A standard mil-spec spring is calibrated for a gas-operated 5.56 carrier; on a softer or differently-pressured system it is often the wrong rate. Swapping to the Tubb lightweight flatwire spring lowers the resistance the action sees, which changes how the bolt or carrier loads and unloads through the cycle. That tunability is exactly why it shows up in builds that have a cycling problem to solve rather than a recoil problem.

On an over-driven blowback action, including AR-9 carbines running a forced reset trigger, the action can cycle faster than the shooter can feed the trigger, and the rate becomes the limiting factor on control. A lighter spring is one of the two levers builders use to bring that rate down, the other being buffer weight. The working method is to start heavy and tune down: confirm function with a heavier buffer and stiffer spring first, then lighten the spring or the buffer in steps until the action is controllable without inducing malfunctions. Note that David Tubb does not list 9mm or PCC among the stated applications; this is a low-pressure flatwire spring that builders adapt to that job, not a spring Tubb markets for 9mm.