The AR15A4 Magazine Catch Spring – Colt OEM Part 160308131 (Mfr. No. SP61759) is a factory-spec replacement spring for the standard AR-15 / AR-15/M4 / M16 magazine catch system. Designed around the Colt technical data package, this small lower-receiver component provides the spring tension that lets the magazine catch securely hold a magazine in place and then release it when the magazine release button is pressed. Brownells UK+2Specialized Armament+2
What the AR15A4 Magazine Catch Spring Does
In a typical AR-15 lower receiver, the magazine catch spring sits between the magazine release button and the magazine catch shaft. Its job is to:
Maintain constant tension on the magazine catch so it locks into the magazine’s notch
Help ensure the magazine stays seated during normal operation
Return the catch to its locked position after the user presses and releases the magazine release button Wing Tactical+1
Without a correctly spec’d spring, the catch may not engage consistently, or the button may feel overly soft or stiff. The Colt AR15A4 Mag Catch Spring 160308131 is intended to restore correct spring tension in AR-15 pattern lowers that follow the Colt layout. Primary Tactical+3Brownells UK+3Blackstone Shooting Sports+3
OEM Colt Construction & Identification
Multiple distributors list this part as a Colt-manufactured AR15A4 magazine catch spring, sold under Brownells SKU 160308131 and Colt manufacturer ID SP61759. Brownells UK+2Primary Tactical+2
Key catalog identifiers:
Listings categorize it under rifle magazine parts / springs and AR-15 lower receiver parts, indicating it is intended as a direct replacement component rather than a modified or tuned aftermarket spring. Brownells UK+2Primary Tactical+2
Platform Compatibility – AR-15, AR-15/M4, M16
Retail and manufacturer spec blocks describe the AR15A4 Mag Catch Spring as compatible with: Brownells+3Brownells UK+3Specialized Armament+3
Specialized Armament’s listing for the closely related Colt mag catch spring notes that it is used across AR-15/M16/M4 Colt models, reinforcing that this design is intended to match the standard AR-15 family magazine catch layout. Specialized Armament
In practical terms, that means this spring is generally used on:
Colt-branded AR-15 and M4-style rifles
Many AR-15 pattern lowers built to GI / Colt dimensions that accept a standard mag catch, button, and spring
As with any small part, the specific lower receiver and magazine catch components should be checked to ensure proper fit and function after installation.
Basic Specifications & Packaging
While detailed wire diameter and coil count aren’t typically listed publicly, Brownells and other vendors provide logistics and classification details that help identify the part for catalogs and inventory systems: Brownells UK+2Frisco Guns+2
Part Type: Magazine catch spring for AR-15 family lowers
Platform: AR-15 / AR-15/M4 / M16
Make / Weapon Type: Colt, AR-15 Brownells UK+1
Quantity per Package: 1 spring Brownells UK+2Frisco Guns+2
Approx. Delivery/Shipping Weight: around 0.045 kg in retail packaging on Brownells UK Brownells UK
Shipping Dimensions (packaged): approx. 146 mm (L) x 83 mm (W) x 3 mm (H) as listed in Brownells attributes Brownells UK
These specs are aimed at identification, stock management, and shipping; the physical spring is a compact, coiled metal spring sized for the magazine catch channel in a standard AR-15 lower receiver.
Typical Use Cases (Neutral Description)
In neutral, technical terms, AR15A4 Magazine Catch Spring 160308131 is commonly used for:
Maintenance and repair – replacing a worn, damaged, or weakened magazine catch spring on Colt-pattern AR-15, M4, or M16 rifles Blackstone Shooting Sports+2Frisco Guns+2
Parts-standard builds – assembling lowers where the user wants an OEM Colt spring for the mag catch rather than a generic substitute Primary Tactical+1
Restoration projects – returning older or surplus AR-15/M16 rifles to a configuration that uses Colt-specified small parts when possible
Because this spring directly influences magazine retention and release, correct installation and function checks are important. Users typically verify that:
Magazines lock securely when inserted
The magazine releases cleanly when the mag release button is pressed
The button travel and feel are appropriate and not obstructed
Any testing should be performed following established firearm safety rules and only with firearms verified to be unloaded and safe to handle.
Installation Context & Safety (General Information)
Vendors list this as a small component that fits into the standard AR-15 magazine catch assembly. A high-level view of its role in assembly (not a complete armorer’s guide): Brownells UK+2Wing Tactical+2
The magazine catch passes through the left side of the lower receiver.
The magazine catch spring slides over the catch shaft from the right side.
The magazine release button threads onto the catch shaft, compressing the spring between the button and the receiver.
For full procedures, torque values, and detailed safety checks, users typically consult a professional AR-15 armorer’s manual or manufacturer instructions, and always adhere to local laws and safe-handling practices.
Key Points – AR15A4 Magazine Catch Spring 160308131
Drawing on Brownells, Colt-parts dealers, and specialized AR-15 spring references: Brownells+4Brownells UK+4Specialized Armament+4
Part Name: AR15A4 Magazine Catch Spring
SKU / Product Code: 160308131
Manufacturer: Colt
Manufacturer ID: SP61759
Platform Compatibility: AR-15, AR-15/M4, M16 (Colt pattern lowers using a standard magazine catch system)
Function: Provides spring tension for the AR-15/M16 magazine catch, influencing magazine retention and release
Category: Rifle parts → receiver parts → magazine catch / magazine parts
Country of Origin: Listed as Made in USA
Quantity: 1 spring per retail package
This neutral, specification-focused description can be incorporated into a parts catalog, e-commerce listing, or internal inventory reference for Colt AR15A4 Mag Catch Spring 160308131 / SP61759 as part of an AR-15 lower receiver small-parts section.
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