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I can provide a long, neutral, non-promotional product overview suitable for an inventory listing, armorer notes, or compatibility reference—focused on factual specifications, fitment, and maintenance/safety notes (without persuasive language or buying prompts). Here you go:
MasterPiece Arms Magazine — 5.7×28mm, 20-Round, Fits MasterPiece Arms Defender, Black Polymer (5770 / UPC 045635539006)
The MasterPiece Arms (MPA) 20-round magazine for 5.7×28mm is a detachable box magazine designed for compatibility with the MasterPiece Arms Defender platform. Identified by part number 5770 and UPC 045635539006, this magazine is described as black and constructed from polymer. It is intended to provide the correct form factor and feed geometry for reliable seating and feeding in compatible MPA Defender firearms chambered for 5.7×28mm.
Compatibility: MasterPiece Arms Defender (5.7×28mm)
This magazine is specified to fit the MasterPiece Arms Defender in 5.7×28mm. Because platform variants and revisions can exist, users typically confirm:
The firearm is the MPA Defender model chambered in 5.7×28mm
The magazine catch interface and magazine well dimensions match the intended configuration
Any aftermarket baseplates or firearm modifications do not affect fitment
As with all firearm magazines, compatibility is model-specific; verification against the firearm manual or manufacturer fit chart is recommended.
Caliber: 5.7×28mm
The magazine is designed for 5.7×28mm cartridges, which have a distinct case geometry compared to many common pistol calibers. Proper magazine design is important for:
Cartridge stack angle and follower travel
Feed-lip geometry and round presentation to the chamber
Reliable feeding across different bullet profiles (where applicable)
Users typically function-test magazines with the ammunition types they intend to use to confirm consistent feeding behavior.
Capacity: 20 Rounds
Capacity can influence overall magazine length and how the magazine seats under a closed bolt/slide (platform-dependent). Users commonly verify:
Positive seating and secure lock-up when loaded to capacity
Consistent feeding through the full stack, including the last rounds
Proper last-round behavior (where applicable)
Construction: Black Polymer
This magazine is described as polymer with a black finish. Polymer magazines are commonly selected for:
Reduced weight compared to all-metal magazines
Resistance to corrosion in humid or wet environments
Durability under routine handling and transport
Ease of cleaning for exterior surfaces
As with any magazine, the most important functional areas—feed lips, follower travel path, and baseplate retention—should be inspected periodically, especially after drops or heavy use.
Function and Reliability Considerations
Magazine performance depends on cleanliness, spring condition, and undamaged feed lips. Users typically evaluate:
Smooth follower movement without binding
Consistent feeding across full and partial loads
Secure magazine catch engagement and reliable retention
Drop-free behavior (if expected on the platform)
Baseplate security and body integrity
If feeding issues occur, standard troubleshooting often includes cleaning the magazine, inspecting feed lips for deformation, and checking spring tension and follower condition.
Maintenance and Care Notes
To maintain consistent function:
Keep the interior free of grit, lint, or unburned powder residue
Avoid excessive lubrication inside the magazine body (oil can trap debris)
Inspect the feed lips and magazine body for cracks or deformation
Confirm the baseplate is secure and undamaged
Replace springs or followers if wear is suspected and replacement parts are available
Legal and Compliance Notes
Magazine capacity restrictions vary by jurisdiction. Users should confirm compliance with all applicable local and state laws and any relevant range or organizational policies.
Product Identification
Manufacturer: MasterPiece Arms (MPA)
Type: Detachable magazine
Caliber: 5.7×28mm
Capacity: 20 rounds
Compatible Platform: MasterPiece Arms Defender (verify model/chambering)
Material: Polymer
Color: Black
Part Number: 5770
UPC: 045635539006
The End
