Firearms Alchemy | Stonewall Krebs SBR AK


Turning Krebs Yugo AK pistol into an SBR makes it a more practical firearm.

Turning Krebs Yugo AK pistol into an SBR makes it a more practical firearm.

Certain weapons evolve over time as users search for their best utility. Previous experiences with other AK-type pistols led Bill Randolph, co-owner of Stonewall Arms LLC, to an appreciation of the handling and performance enhancements gained by converting the AK pistol into an SBR by adding a stock.

Bill Randolph is behind the rather unique AK SBR featured here, which started as a Krebs Custom Yugo AK pistol. I hesitate to use the term Krinkov to describe the weapon because it’s not totally accurate. The weapon went through various transformations and stands distinct in its own right.

This is something Bill is very familiar with, considering that Virginia-based Stonewall Arms has been in business for several years handling Class III items for individuals, law enforcement and commercial customers. Stonewall Arms is also a successful FFL dealer specializing in long guns, pistols, accessories, and ammunition in the tactical and personal defense realms.

KREBS CUSTOM YUGO AK PISTOL

Almost immediately after acquiring the Krebs Custom Yugo AK pistol, Bill viewed it as a viable candidate for a personal SBR project—one of the perks of being a gun shop owner. SBR rifle kits in 7.62x39mm are currently scarce, and the Krebs Yugo AK pistol seemed a perfect alternate. After all, it came from Krebs Custom and thus benefits from Marc Krebs’ years of experience working with the AK platform.

Yugo SBR handled as expected, due to shortened barrel and AK reliability. EVTC 360-degree range allows vehiclebased training scenarios.

Yugo SBR handled as expected, due to shortened barrel and AK reliability. EVTC 360-degree range allows vehiclebased training scenarios.

Even without firing a live round, the benefits of the Krebs Custom Yugo AK pistol could be detected in the smoothness of the action, trigger pull, quality of re-finish, and overall weapon feel. Test firing it could not be resisted while waiting for the BATF to approve the paperwork to convert it into an SBR.

While interesting, the Yugo AK pistol lacked much in terms of accuracy past normal handgun ranges, with the added negatives of weighing nearly six pounds and having the muzzle blast of a rifle round. While definitely categorized as a fun firearm, the AK in its pistol form is limited in its effectiveness.

Turning the Krebs Yugo AK pistol into an SBR makes it a more practical firearm. Yes, the ten-inch barrel sacrifices some performance versus 16-inch barrels, but this is the price for any SBR. Increased handling and portability more than compensate for any velocity lost.

The ten-inch barrel length is longer than an 8.5-inch barreled Krinkov, but this is a viable compromise considering alternatives are slim when searching for a 7.62x39mm Krinkov kit. The Yugo AK has a unique front gas block and sight compared to other full-size AKs, and the rear sight is modified for shorter ranges.

PERFORMANCE UPGRADES

Certain performance upgrades were sought in converting the Krebs Custom Yugo AK pistol into an SBR configuration. The first, and most important, involved modifying the Yugo’s rear trunnion to add a stock.The lack of a rear stock associated with the Yugo AK pistol nestled in the shoulder definitely impacts effectiveness.This is based on multiple points of contact represented by a shoulder stock as compared to a handgun. This consists of shoulder, cheek, and hands spread farther apart for more stability compared to a handgun.

Yugo surplus ammunition produced little flash signature. Egyptian ammo provided a pyrotechnic show at times.

Yugo surplus ammunition produced little flash signature. Egyptian ammo provided a pyrotechnic show at times.

Bill had the Yugo’s rear trunnion modified and added a clubfoot AK stock. This type of stock pattern is more typically found on the RPD/RPK family of light machine guns. A clubfoot buttstock is designed to allow the user to fire from the prone position more comfortably as typical of a light machine gun. However, the shorter length of pull and profile proved no detriment with the Yugo SBR, especially if loaded up with chest rig or other gear.

Bill sought further enhancements to the Yugo AK SBR conversion besides just adding a rear stock, in an effort to get the most out of the Krebs Custom AK pistol build. A way to mount a red dot optic—a vast improvement over the standard open sights—on the Yugo AK was explored. I urged Bill to go with a Krebs Custom forend rail, as I have this arrangement on two different rifles. Bill took a different path due to his intention of having the rifle “dip” coated (more on this later).

A StormWerkz scope mount was drilled and tapped into the Yugo’s top cover, fitting in between the rear sight and hinge mechanism. The StormWerkz mount was simple to install securely to the top cover, as clear instructions were provided.

StormWerkz scope mount was drilled and tapped into Yugo AK SBR’s top cover. Trijicon RMR was chosen for Yugo based on its lack of reliance on battery power and compact size.

StormWerkz scope mount was drilled and tapped into Yugo AK SBR’s top cover. Trijicon RMR was chosen for Yugo based on its lack of reliance on battery power and compact size.

A Trijicon RMR was the sight chosen for the Yugo AK SBR based on its reputation for hardiness, lack of reliance on battery power, and compact size that takes nothing away from the AK SBR’s handling and feel. The Trijicon RMR offered the capability of engaging multiple targets in rapid sequence as compared to open sights. The RMR’s large field of view, especially with both eyes open, and single focus plane are far superior to the Yugo SBR’s iron sights.

AESTHETIC UPGRADE

Bill’s last modification was more aesthetic than functional in nature. He decided to take an already special AK and “dip” it with camouflage pattern to create something truly unique.

Bill turned to a local water transfer printing company, Virginia Hydro Designs, to have a Desert Tiger Stripe camouflage pattern installed on the Yugo SBR’s stock and forend.

Virginia Hydro Designs imparted Tiger Stripe Desert camouflage pattern on Yugo SBR’s stock, forend and magazine.

Virginia Hydro Designs imparted Tiger Stripe Desert camouflage pattern on Yugo SBR’s stock, forend and magazine.

Virginia Hydro Designs’ water transfer method allows for the application of printed patterns onto three-dimensional objects. A chosen film design is laid in a specially designed dipping tank, and an activator chemical is applied to the film. This activator dissolves the film into liquid ink, which stays afloat on the surface of the water. Then an object, in this case the Yugo SBR’s stock and forend, is dipped slowly through the floating ink and the pattern is transferred to the object. The finish is protected with a professional-grade clear coat. The clear coat that protects the finish is just as durable as an automotive paint finish and provides UV protection.

RANGE EVALUATION

The Yugo AK SBR was evaluated at Echo Valley Training Center (EVTC) in West Virginia. This private facility has multiple 100-yard enclosed bays and a 360-degree drive-in range, all capable of handling many students conducting square-range drills or more dynamic types of training. In conjunction with the individual training bays, EVTC features multi-stepped target berms that are strewn with reactive steel targets from TacStrike, fluid-drained automobiles, and moving targets at ranges varying from 150 to 350 yards.

After verification of 25-yard zero, evaluation commenced with a function test involving firing several magazines in rapid succession.After verification of 25-yard zero, evaluation commenced with a function test involving firing several magazines in rapid succession.

After verification of 25-yard zero, evaluation commenced with a function test involving firing several magazines in rapid succession.

The range evaluation followed an established protocol for combat rifles. After a quick verification of 25-yard sight zero, evaluation commenced with a function test involving firing several magazines in rapid succession at various TacStrike steel man targets and vehicles dotting the range.

While not scientific, this is a good way to establish a baseline for reliability. If an AK-type weapon does not have pristine reliability, its major attribute is nullified. A more comprehensive 100- yard sight zero confirmation took place after functionality had been established.

Variety of drills, including shooting on the move, reloading, and engaging multiple targets, helped put Yugo SBR through its paces.

Variety of drills, including shooting on the
move, reloading, and engaging multiple targets,
helped put Yugo SBR through its paces.

AMMUNITION

Brass-cased Egyptian and Yugoslavian 7.62x39mm surplus ammunition acquired from Century International Arms was used for the bulk of the testing, with Wolf Ammunition Polyformance 122-grain and Military Classic 124-grain loads also used.

Accuracy was acceptable for an AK, or any other combat rifle using iron sights or non-magnified optics, with groups of three to four inches at 100 yards. The muzzle device did a decent job of minimizing flash, but every so often a ball of flame would jet out from the cylinder-shaped muzzle device.

I say muzzle device because what is fastened on the Yugo’s muzzle is neither a true brake nor flash hider, but rather a gas expansion chamber to ensure reliable functioning on full-auto—not an issue with the semi-auto SBR under review here.

Paying attention to ammunition types paid dividends in terms of flash signature from the SBR, with the Yugo surplus producing little signature, while the Egyptian ammunition provided quite the pyrotechnics at times.

One downside of most surplus ammunition is that it utilizes corrosive primers, which the Russians and other ex-Soviet bloc states and clients insisted on due to concerns with cold-weather ignition and the long-term storage capabilities of corrosive primers. The Egyptian ammunition is labeled as noncorrosive, but was handled as if it were corrosive to take no chances.

As long as proper cleaning methods are followed to remove elements left over from the primer residue, corrosive ammunition is not the destroyer of rifles that many will lead you to believe. During several range visits in both its pistol and SBR forms, the Krebs Custom/ Stonewall Yugo SBR sent several hundred rounds downrange. The weapon was cleaned between range visits due to the use of corrosive ammunition.

OTHER RANGE TESTS

Further range testing of the Krebs/ Stonewall Yugo SBR consisted of repeating numerous drills and exercises experienced via training with Norone Corp, Jason Falla’s Redback One, Storm Mountain, and Tactical Response. Firing while moving as well as behind cover, reloading drills, transitions between shoulders depending on cover orientation, and engaging multiple targets arranged around no-shoot targets all helped put the Yugo SBR through its paces.

While not as subtle or tame as an AR-15 or AK-74, the Yugo SBR’s muzzle blast and recoil were not prohibitive and allowed for fast double and triple taps on selected targets, especially at CQB distances. The club foot stock performed well. Its downward cant and shorter length of pull were assets.

The Trijicon RMR assisted in engaging targets at close distances, with the red dot easy to pick up rapidly while still permitting more than enough accuracy out to about 200 yards.

The Yugo SBR handled as expected, benefiting from the shortened barrel combined with AK reliability. Krebs Custom tuning could be detected in the smoothness of the manually operating action and slickness of magazine changes.

The EVTC 360-degree range allows vehicle-based training scenarios. This is a situation where the Yugo SBR comes into its own, with potent firepower contained in a compact and reliable package. Targets of opportunity located around the range, such as car hulks, manhole covers, and TacStrike steel targets, were engaged repeatedly.

TACTICAL WEB GEAR

Tactical web gear from BlackHawk and Velocity Systems/Mayflower was utilized to help test the customized Yugo SBR. The Mayflower 7.62 Hybrid Chest Rig is a low-profile vest built to be used in law enforcement and military environments when a small, lightweight package is necessary for climbing over obstacles or maintaining a low profile.

The Mayflower Chest Rig is designed to carry three 7.62mm magazines in an integral pouch with an adjustable shock cord retention system closure. The front of the magazine pouch has three general- purpose pouches sized to carry the tools of the trade, such as mini binoculars, mini laser rangefinder, GPS, cell phone, and PDA.

The sides of the Chest Rig have three rows of PALS webbing to tailor the remainder of the Chest Rig for the mission. The H-style harness features loops to route antennas, comms wires, and hydration bladder tubing. All buckles are ITW-Nexus IR and materials and workmanship are 100% made in the USA. The Mayflower Hybrid Chest Rig works well with Velocity Systems plate carriers if the mission dictates.

Some will question if the hassle for an SBR is worth it. The answer, as with most things related to firearms, is personal preference. The Krebs Custom Yugo AK pistol turned into an SBR by Bill Randolph combined with enhancements turned out to be a good investment of time and money due to its increased shootability and reliability.

Not much more can be asked from a rifle.

Stonewall Arms
(540) 535-2190
www.stonewallarms.com

Krebs Custom Inc.
(847) 487-7776
www.krebscustom.com

BLACKHAWK!
(800) 694-5263
www.blackhawk.com

Century International Arms
(800) 527-1252
www.centuryarms.com

Echo Vall ey Training Center
(540) 450-7998
www.echovalleytrainingcenter.com

TacS trike Systems Inc.
(540) 751-8221
www.tacstrike.com

Velocity Systems
(703) 707-5280
www.velsyst.com

Virginia Hydro Designs
(540) 877-5585
www.virginiahydrodesigns.com

Wolf Ammunition
(888) 757-9653
www.wolfammo.com

About Author

Todd Burgreen

Todd Burgreen has been a freelance writer for the last 20 years with articles appearing in numerous publications. He has attended numerous personal defense, team tactics, firearms, and driving courses over the years from some of the most influential training personalities and schools in the country.

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