Product Description
The HDA3 is a modular stock/brace system developed from a collaboration between Haga Defense and A3 Industries. The HDA3 was designed specifically to integrate seamlessly across dozens of firearm platforms without sacrificing strength or aesthetics to do so.
The HDA3 fills a footprint that the gun industry has already come to love while providing a level of quality, modularity and durability that has never been offered in a similar package. The HDA3 is designed, manufactured and assembled in the USA.
FEATURES:
- Folding Steel Hinge: The HDA3 utilizes a steel hinge assembly, ensuring a strong lockup in the straight and folded position that will not degrade with use. The HDA3 will by default fold to the left side canted at 3.5 degrees. Right side folding variants will be available at a later date.
- Strong Bones: The HDA3 is designed with all metal internal components for maximum durability. An aluminum cheek riser button and length adjustment latch both interface with an extruded aluminum spine that ties into the steel hinge.
- Stock & Brace Configurations: The HDA3 is available as a stock with an injection molded extension and rubber buttpad or as a brace with an injection molded extension designed to accept a variety of arm braces. See below for brace compatibility.
- Adjustment: The HDA3's length can be adjusted in .5" increments between 7 positions. The cheek riser can be used in three positions. In the lowered position, raised .25" or raised .5". Both adjustments can easily be manipulated one-handed.
SPECIFICATIONS:
- Mounts to SIG SPEAR LT & MCX
- 6061 hardcoat anodized aluminum adapter
- Adapter dimensions: 2.5" Tall by 1.25" Wide
- Will NOT fit .308 SPEAR
- Will NOT fit AR15s with SIG MCX Adapter (2401191-R)
- Length:
- Stock configuration: 7.84-10.84"
- Brace configuration (without brace): 8.16-11.16"
- Weight:
- Stock configuration: 1lb 3.3oz
- Brace configuration (without brace): 1lb 1.8oz
- Heavy duty Locking Hinge
- Nitride coated 17-4 stainless steel
- Folds to the left side canted at 3.5 degrees
- 7 Position extrusion with length adjustment in .5" increments
- 6061 aluminum extrusion with 7075 aluminum locking latch. Hardcoat anodized
- 3 Position Cheek Riser (0, +0.25" & +0.50")
- Polymer construction with hardcoat anodized 6061 aluminum adjustment button
- Textured Butt-pad (stock) manufactured from injection molded "rubber-like" Santoprene TPE
- High-Strength Polymer: All polymer components are injection molded 30% glass fiber reinforced nylon.
- Sling Mounts: There is a sling loop as well as two steel QD mounting points at the rear of the HDA3. There is one additional QD mount machined into the aluminum adapter.
- Color: Available in Black, FDE, ODG and Gray.
- Designed, manufactured and assembled in the USA
SPEAR LT - MCX NOTES:
This HDA3 variant is exactly the same as the 1913 variant but includes a nylon plug(s) that will fill the unsightly gap created between the bottom of the stock and the lower receiver. There are two plugs included. One will work with the factory SIG grip and the other is designed to work with flat top style grips. The photo below shows the two options.
NOTICE: You WILL NOT be able to operate the charging handle if the cheek riser is raised. The cheek riser can be quickly moved out of the way but know that pulling back the charging handle all the way will not be possible in the middle or top position. See image below. 
PISTOL BRACE CONFIGURATION:
When purchasing the pistol brace configuration the HDA3 will be shipped with a brace mount not a butt-pad. The brace mount will accept tube mount style (1.195" Dia.) pistol braces which are NOT included.
Braces that are compatible with the HDA3 are listed below and can be purchased separately
- A3 Steady Brace (click here)
- Gear Head Works Tailhook MOD1 (click here)
- Gear Head Works Tailhook MOD1C (click here)
- Midwest Ind. Arm Brace Hook - modification required (click here)
DISCLAIMERS: Customer is responsible for being aware of local, state, and federal laws regarding the use of this product.
ADJUSTABLE CHEEK RISER
LOCKING STEEL HINGE
ADJUSTABLE LENGTH
PISTOL BRACE VARIANT
BUILT-IN QD SLING MOUNTS
RUBBER BUTTPAD
OPERATION (VIDEO):
INSTALLATION:
1. Physically and visually check that the firearm is unloaded and that the magazine and ammo have been removed.
2. Slide the stock into position on the rear mounting rail. Ensure that the top of the stock is flush with the top of the receiver and make sure that the charging handle will not strike or catch on the top of the stock.
3. Before tightening the stock insert the desired nylon plug into the stock's mounting channel.
4. Using a 4mm hex wrench or bit, tighten the adapter screws evenly until the stock is tight on the mounting rail. We recommend starting at about 30 in-lbs. Adjust accordingly but do not overtighten.
