This factory HK416 buffer spring is the genuine Heckler & Koch recoil spring for the MR556A1 and the wider HK416 family (brand part no. 50233166). The buffer spring is the component that returns the bolt carrier to battery on every single shot, which makes it one of the highest-wear parts in the rifle and one of the least glamorous to think about until it causes a malfunction. A tired spring shows up as sluggish cycling, failures to return fully into battery, and inconsistent ejection patterns. Replacing it is cheap insurance, and using the factory component rather than a commercial substitute matters on a piston-driven rifle with its own recoil timing. Buy one to fix a problem or buy one to keep in the spares box before you have a problem. Heckler & Koch specifies that rifle parts be installed by a qualified gunsmith.

Key Specifications

• This is a genuine HK factory component, not an aftermarket copy built to approximate dimensions.
• The spring is made from high-quality steel for consistent rate and resistance to taking a set over time.
• Primary fitment covers the MR556A1, the civilian semi-automatic counterpart to the HK416.
• It also fits the HK416 family including the A5 and the M27, sharing the same recoil system dimensions.
• The spring is compatible with mil-spec AR-15, M4, and M16 receiver extensions, broadening its usefulness as a spare.
• It is a recognized high-wear maintenance item, making it a sensible part to keep on hand before a failure occurs.
• HK recommends installation by a qualified gunsmith, consistent with their guidance for all rifle components.

Frequently Asked Questions

Will this fit a standard AR-15? Yes. While it is the factory spring for the MR556A1 and HK416, it is compatible with mil-spec AR-15, M4, and M16 receiver extensions as well.

How do I know when my buffer spring needs replacing? Sluggish cycling, failure to fully return to battery, and erratic ejection are the common signs of a spring that has taken a set and lost rate.

Is this a genuine HK part? Yes, it is an original component manufactured by Heckler & Koch, not an aftermarket equivalent.

Buy the Heckler & Koch HK416 Buffer Spring

Spare springs are the sort of thing nobody orders until a rifle starts short-stroking at the worst possible moment. This one costs less than a box of match ammunition and keeps a serious piston rifle running the way it was designed to. Browse it with our other rifle parts and order from our Lubbock, Texas shop for fast direct shipping.