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Questions & Answers
I am not seeing anywhere that shows how to install on the Kuna. The back of the Kuna is 1913 which is much different than the brace.

This doesn’t mount to the 1913 Picatinny on the back of the Kuna, this removes that entirely. If you look at the take apart guide in your Kuna’s manual you’ll see that that part is removable. This stock inserts into that section of the upper receiver instead, so it’s actually better in that it shrinks the overall length of the weapon when mounted. That being said there also is a version of this stock that is sold with the ability to mount to 1913 picatinny, but it’s not worth it for the Kuna since direct mount will be a more solid connection.

by CasualOutlaw, Verified Owner, March 14, 2026
Customer Reviews
Helpful Positive Review
Perfect stock for the kuna by Cobra man, Verified Owner, May 4, 2026
So far this stick has been perfect for the kuna. It’s well built, the metal frame really helps make it feel like premium product. The cheek riser is placed in the perfect spot and it has plenty of adjustability.
1/1 found this helpful
Most Recent Reviews
Probably the best by Mike Jones, Verified Owner, April 8, 2026
Saw this on YouTube by the guys at classic firearms mention it as one of the best if not the best it was their favorite so I got it. I’ve been trying it out. It’s been about a month now and I would say this thing is as advertised. It’s probably the b...
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Product Info for A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock

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. 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.image

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 for A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock:

Manufacturer: A3 Industries
Gun Type: Rifle
Gun Make: Springfield Armory
Gun Model: Springfield Armory Kuna
Length: 7.9 in
Condition: New
Stock/Brace Material: Polymer

Features of A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock

  • Aluminum Extruded Spine
  • 3 Position Adjustable Cheek Riser
  • Rubberized Buttpad
  • 7 length of pull adjustments
  • HD Steel folding hinge

Package Contents:

  • A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock

A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock Orderable Models

List of Orderable Models

  • A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock, Black, HDA3-KUNA-A3-S-LF-BLK , MPN: HDA3-KUNA-A3-S-LF-BLK , UPC: 810151875248 , Code: 69H-RSF-HHGB1-HDA3-KUNA-A3-S-LF-BLK
  • A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock, Flat Dark Earth, HDA3-KUNA-A3-S-LF-FDE , MPN: HDA3-KUNA-A3-S-LF-FDE , UPC: 810151875255 , Code: 69H-RSF-HHGB1-HDA3-KUNA-A3-S-LF-FDE
  • A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock, Grey, HDA3-KUNA-A3-S-LF-GRY , MPN: HDA3-KUNA-A3-S-LF-GRY , UPC: 810151875279 , Code: 69H-RSF-HHGB1-HDA3-KUNA-A3-S-LF-GRY
  • A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock, Olive Drab Green, HDA3-KUNA-A3-S-LF-ODG , MPN: HDA3-KUNA-A3-S-LF-ODG , UPC: 810151875262 , Code: 69H-RSF-HHGB1-HDA3-KUNA-A3-S-LF-ODG

A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock Unavailable & Discontinued Models

List of Unorderable Models

  • DEMO, A3 Industries Hda3 Hybrid Polymer Springfield Kuna, Folding Rifle Stock, Flat Dark Earth, HDA3-KUNA-A3-S-LF-FDE , MPN: HDA3-KUNA-A3-S-LF-FDE-DEMO , Code: 69H-RSF-HHGB1-HDA3-KUNA-A3-S-LF-FDE-DEMO-OB-A
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Last updated 2026-07-29 UTC.