Description
HDA3 Stock and Brace System for HK MP5, SP5
The HDA3 is a modular, USA-made stock and brace system developed by Haga Defense and A3 Industries. Built for strength, adaptability, and cross-platform compatibility, it delivers premium rigidity, smooth adjustability, and long-term durability without compromising aesthetics.
Features:
- Heavy-duty steel hinge locks solidly open or folded. Folds left at a 3.5° cant.
- All-metal internals, including an aluminum cheek-riser button and length-adjustment latch tied into an extruded aluminum spine.
- Choose the stock version with molded extension and textured Santoprene buttpad, or the brace-ready version compatible with 1.195″ tube-style arm braces.
- Seven length positions in 0.5″ increments. Three-position cheek riser at 0, +0.25″, and +0.50″. Both adjust one-handed.
Specifications:
- Made in the USA
- Adapter: 6061 hard-coat anodized aluminum
- Adapter dimensions: 3.0″ H × 1.84″ W
- Includes rubber buffer
- Stock length: 8.6″–11.6″ (from takedown-pin center)
- Brace mount length: 8.9″–11.9″ (without brace attached)
- Weight:
- Stock weight: 1 lb 6.2 oz
- Brace mount weight: 1 lb 4.4 oz
- Nitride-coated 17-4 stainless steel, left-folding hinge
- Extension: 7-position 6061 aluminum extrusion with 7075 locking latch
- Cheek Riser: 3-position polymer riser with anodized aluminum button
- Materials: 30% glass-fiber reinforced polymer components
- Textured Santoprene TPE buttpad (stock only)
- Sling mounts: rear sling loop, two steel QD points, one QD point on the adapter
Compatible With:
- MP5, SP5
- In-spec clones and custom builds
