Buffer and Spring Combos for AR15 Tuning By RTF3TX Gunsmithing Editorial Team · Updated 2026-08-30 Newton's third law drives AR-15 cycling: expanding gas pushes the bolt carrier rearward while equal force propels the bullet forward. Buffer weight controls carrier momentum and dwell time, directly affecting reliability. Forced reset triggers demand precise buffer tuning—typically H2 or H2.5 for carbine-length gas systems—since incorrect mass causes trigger freeze, short-stroki