AR15 Buffer Spring

What Is an AR-15 Buffer Spring

An AR-15 buffer spring is a compression spring housed inside the buffer tube (receiver extension) that returns the bolt carrier group (BCG) to battery after each firing cycle and controls the rate at which the BCG cycles. The buffer spring works in conjunction with the buffer weight to determine bolt speed, recoil impulse, and cycling reliability. The buffer system consists of 3 components: buffer tube, buffer, and buffer spring.

TactaBlue stocks AR-15 buffer springs from Sprinco, JP Enterprises, Aero Precision, Spike's Tactical, Strike Industries, and other manufacturers in carbine, rifle, pistol caliber, and flat wire configurations.

What Does the Buffer System Do

The AR-15 buffer system absorbs the rearward energy of the bolt carrier group during firing, stores that energy in the compressed spring, and returns the BCG forward to strip a new round from the magazine and lock into battery. When the rifle fires, expanding propellant gases enter the gas port in the barrel and travel through the gas tube into the gas key on the BCG. This gas pressure drives the BCG rearward against the buffer and buffer spring.

The buffer spring compresses as the BCG travels rearward. The spring then releases its stored energy to push the buffer and BCG forward. The BCG strips the top round from the magazine, pushes the round into the chamber, and the bolt rotates into the locked position. This complete cycle occurs in approximately 6-10 milliseconds.

Types of AR-15 Buffer Springs

AR-15 buffer springs are available in 4 main types: carbine, rifle, flat wire, and extra power. Each type has different length, coil count, wire diameter, and spring rate characteristics.

Carbine vs Rifle Buffer Springs

Carbine buffer springs measure 10.0625 inches (255.6 mm) in free length and have 37-39 coils. Carbine springs fit inside carbine-length buffer tubes measuring 7.25 inches (184.2 mm) in length. Rifle buffer springs measure 12.75 inches (323.9 mm) in free length and have 41-43 coils. Rifle springs fit inside rifle-length buffer tubes measuring 9.625 inches (244.5 mm) in length.

Carbine buffer springs are used in collapsible-stock AR-15 rifles, which represent the majority of modern AR-15 configurations. Rifle buffer springs pair with fixed A1 and A2 stocks. Carbine and rifle buffer springs are not interchangeable because they differ in free length and buffer tube dimensions.

Pistol Caliber Buffer Springs

Pistol caliber carbine (PCC) buffer springs are designed for AR-15 platforms chambered in 9mm, .40 S&W, and .45 ACP that use blowback or radial delayed blowback operating systems. PCC buffer springs have higher spring rates than standard carbine springs because blowback actions generate more rearward bolt velocity than gas-operated systems. The Kaw Valley Precision PCC buffer spring and Spike's Tactical 9mm buffer assembly are 2 purpose-built PCC options.

Flat Wire Buffer Springs

Flat wire buffer springs use a rectangular cross-section wire instead of the round wire used in standard coil springs. Flat wire springs provide 15-20% more spring force in the same compressed length compared to round wire springs. The flat wire design reduces the characteristic "sproing" sound that standard round wire carbine buffer springs produce during cycling. JP Enterprises Polished Buffer Spring, Sprinco, and Strike Industries produce flat wire buffer springs for the AR-15 platform.

Flat wire springs maintain consistent spring rates over a longer service life because the rectangular wire distributes stress more evenly across the coil surface. Standard round wire springs typically require replacement after 5,000-10,000 rounds, while flat wire springs maintain rated performance beyond 10,000 rounds.

Extra Power Buffer Springs

Extra power buffer springs have a higher spring rate than standard mil-spec springs and are designed for overgassed, suppressed, or short-barreled AR-15 rifles that generate excessive bolt carrier velocity. Sprinco Red (extra power carbine), Sprinco Orange (extra power rifle), and the Geissele Super 42 braided wire spring provide increased resistance to slow bolt carrier travel and reduce bolt bounce at the rear of the buffer tube.

Aftermarket Buffer System Options

Aftermarket buffer systems address cycling issues caused by overgassed barrels, suppressor use, and ammunition variability.

Geissele Super 42 Braided Wire Spring

The Geissele Super 42 is a 3-strand braided wire buffer spring paired with a proprietary H1, H2, or H3 buffer weight. The braided wire design eliminates the "sproing" sound of standard springs and provides a progressive spring rate that increases resistance as the spring compresses. The Super 42 system fits standard carbine buffer tubes and is compatible with all mil-spec AR-15 lower receivers.

VLTOR A5 Buffer System

The VLTOR A5 buffer system uses a rifle-length buffer spring inside a proprietary A5 buffer tube that measures 8.5 inches (215.9 mm), which is longer than a carbine tube but shorter than a rifle tube. The A5 system provides a longer spring dwell time that smooths the recoil impulse and increases reliability across a wider range of ammunition types and gas system configurations. The A5 system requires an A5-specific buffer tube and is compatible with most collapsible stocks designed for mil-spec carbine tubes.

Buffer Spring Replacement and Diagnostics

Replace an AR-15 buffer spring when 3 symptoms appear: short-stroking (failure to lock the bolt back on an empty magazine), sluggish cycling, or failure to fully return to battery. A worn buffer spring loses 10-15% of its free length compared to a new spring of the same type.

To test buffer spring condition, remove the upper receiver and place the buffer and spring inside the buffer tube. Press the buffer rearward and release. A functional spring returns the buffer forward with authority. A weak spring allows the buffer to return slowly or stop short of the full forward position.

Buffer spring replacement requires no specialized tools. Push in the buffer retainer pin at the rear of the lower receiver, slide the buffer and spring out of the buffer tube, insert the new spring followed by the buffer, and release the buffer retainer pin.

Shop AR-15 Buffer Springs at TactaBlue

TactaBlue (tactablue.com) stocks AR-15 buffer springs from Sprinco, JP Enterprises, Aero Precision, Geissele, Spike's Tactical, and Strike Industries. Browse the full selection of AR-15 accessories including charging handles and grips for your build. All buffer springs sold at TactaBlue are authentic, factory-sealed products from authorized distributors.

TactaBlue ships within one business day and offers free ground shipping on all contiguous U.S. orders. A 30-day return policy applies to eligible items. For questions, contact support@tactablue.com, Monday through Friday, 10 AM to 6 PM ET.