What feature of modern rifles significantly reduces recoil?

The muzzle brake is a device attached to the muzzle of a rifle that serves to redirect and dissipate the gases expended during firing. This redirection can significantly mitigate the rearward force experienced by the shooter, effectively reducing recoil. By altering the gas flow, the muzzle brake counteracts the recoil impulse that would otherwise push the rifle backward into the shooter's shoulder.

Other features, while they may enhance performance or usability, do not have the same direct effect on recoil management. An adjustable stock provides a more comfortable fit for the shooter, but it does not change the mechanics of recoil. Similarly, lightweight materials in the construction of a rifle can affect handling and maneuverability but do not inherently reduce the force of recoil. As for magazine capacity, it relates to how much ammunition the rifle can hold, which has no impact on recoil at all. Thus, the muzzle brake stands out as the feature most specifically designed to minimize recoil.