Spuhr Collapsible Stock Assembly


Bringing the HK G3 into the 21st Century

The HK G3 is still soldiering on more than 50 years after its introduction. Cheap and reliable, the G3 is the western parallel to the AK47. However, its WWII heritage means its ergonomics sorely require updating. The length-of-pull is too long when employing body armor and the modern squared-on stance. The comb was set low for the iron sights, and one can only obtain a chin weld with optics. The two-position collapsible stock of the G3A4 shortened the rifle for transport, but it is uncomfortable to shoot for the author and still does not address the length-of-pull concerns. The Spuhr collapsible stock assembly addresses all these concerns and will equip the AK4B (locally produced G3) of the Swedish Armed Forces.

The Spuhr stock assembly is comprised of the buffer tube, stock and cheek riser. To install, one removes the metal back plate and buffer from the original stock. The buffer tube assembly is then secured to the back plate by the buffer and its countersunk screws. A long spacer (for a standard G3 buffer) or a washer-thin spacer (for a long pneumatic buffer found on HK21/23 and AK4B) is used along with a bolt to secure the buffer to the buffer tube assembly at the rear. The stock is then attached along with the check riser. The Spuhr product fit perfectly on the author’s PTR91 GIR, an American manufactured G3 “clone.”

Spuhr stock assembly and optical front rail. Optic is a Trijicon TA44 1.5x ACOG.


The six-position stock can be adjusted from 40cm to 32cm (trigger to buttpad) to suit various statures and shooting positions. For example, the 1.8m (5 ft 10 ¾ inches) tall author preferred the stock one detent from fully closed for use with body armor, but needed to extend two more detents for a sling-supported prone position. At the lower front of the stock, a spring-loaded lever is pulled down for adjusting length. While different than an AR15 stock, this can be adjusted with one hand after some practice.

The cheek riser is attached at the front via a screw, and the stock slides along a key on its underside. This keeps the cheek riser stationary and independent of stock position. It also helps reduce play between the stock and buffer tube. The author found the standard riser to work well with his Trijicon TA44 ACOG on a high mount. The resultant 50mm offset between optical center and cheek riser is similar to that of an AR-15. Risers in 8mm and 12mm are also available to accommodate large objective scopes and their taller mounts. Note that iron sights are not usable with the stock assembly due to height mismatch, but the improved check weld with optics is more than a fair tradeoff.

A G3 equipped with the R-401 G3 Optical Front Rail is shown next to an AR-15 for sizing reference.

Sling Attachment

The Spuhr product provides two HK hook attachment points on the castle nut endplate. This allows one to convert a two-point sling into a one-point by attaching both ends onto the endplate. This attachment location duplicates the Swedish Armed Forces-issued vapenfäste kolv strap system that wraps around the G3A3 stock just aft of the “hump.”

Shooting Impressions

The Spuhr stock assembly noticeably reduced felt recoil by improving fitment and by placing the stock in-line with the barrel. The adjustable length-of-pull better fit the rifle to users of all stature and allowed the squared-on stance. This imparted better recoil management and protection when using armor. The serrations in the buttplate prevented slippage even against a plate carrier or slick clothing. A rubber pad, to be released in the future, will undoubtedly further improve handling. In contrast with the concave buttpad of the G3A3 fixed stock, the Spuhr product allowed the user to place the rifle higher or lower on the shoulder according to shooting position and preferences. And unlike the convex buttpad of the G3A4 collapsible stock, the Spuhr product did not concentrate recoil into one point.

The original stock had the shoulder contact point below the recoil vector, and that height induced additional muzzle rise that hindered follow-up shots. The in-line positioning of the Spuhr product was well proven in designs like the FG-42 to mitigate such effects, and the result on the G3 was notable.

Note the pull down adjustment for length-of-pull, as well as the HK-style sling attachment eyelet on the castle nut endplate.


Spuhr collapsible stock assembly brought the G3 into the 21st Century with improved ergonomics and recoil management. The six-position adjustable stock improved fit for various statures and shooting positions. The cheek riser improved cheek weld with optics. Lastly, the in-line design of the stock assembly improved recoil management. This reduced both fatigue and time for follow-up shots. These improvements are well worth the consideration of any G3 user.