Tuesday, December 16, 2014

Up Gunning the SKS: The Shernic Bullpup Stock andPride-FowlerRR-Evolution BLK Optic

One of my pet thoughts is that many older firearms designs are often underestimated by the fads of the moment.  One should bear in mind that the designers of weapons did the best they could to come with a tool that would get a job done; for the designers of military weapons, that job could very well have meant the very survival of their country's way of life.  In my early career as a military analyst I always respected the way the mission dictated the machines.   I think it's fun to learn to understand what the strengths and limitations of the solutions they came up with were; because they are so instructive about what solutions would be needed tomorrow.

A Proud History

The SKS-45.  This one's a Chinese Type 56. One of the many that entered the U.S. in the 1980's

The Samozaryadnyj Karabinsistemy Simonova or SKS was originally designed as a closing engagement weapon for the infantry element of mobile tank armies.  In this role, foot troops were in the role of security for tanks and not fully committed until the end game of an attack.  It was a solution designed to compete with the threat of the other massive mobile tank army that fought the Soviets, the armies of Nazi Germany.  It competed in this mission role with the very similar German Stg 44 and, in the USSR, gave way after the war to the AK-47.  It is a 500 meter and under battle envelope system who's concept carries on today in, among other things, the U.S. M-4 version of the M-16 series weapons system.

The SKS did not serve in the Soviet armies for very long.  It proved more susceptible to dirt than the AK-47 but, like so many rifles of it's time, soldiered on being supplied to and manufactured by allies and client states in massive numbers.

The SKS is today considered to be somewhat of a "poor man's" rifle.  They were rare in the 1960's with just a few samples making their way to the United States as Southeast Asian war trophies. Following the end of the Vietnam War, as America knew it, in 1975, a rather odd period of animus broke out between the Vietnamese and Chinese.  The Chinese realized that their southern neighbor and Russian ally now had the most technologically advanced tank army on the Asian mainland since the Imperial Japanese Army of World War II.  For a time, age old regional tensions dating from the age of iron escalated enough that the Chinese began to stockpile weapons on their southern frontier.

Eventually these tensions subsided and the era of economic trade with the West began.  In the late 1980's, one of the things the new breed of Chinese entrepreneurs began to ship to America were SKS semi-automatic rifles.  They sent them in such quantity at prices so low that US manufacturers began to clamor for import controls.  Later on, after the end of the Cold War, SKS's from Warsaw Pact and former Soviet war reserve arsenals began to arrive as well.  They remain low priced semi-automatic alternatives to the .30-30 Winchester for short range hunting and a good value solutions versus the late-comer .300 AAC Blackout rifles that fire a cartridge ballistically identical to the 7.92x39mm Soviet.  If you really want to, you can even make a subsonic 7.62x39mm round using pistol powders in charge weights in the .45 ACP range and heavy .303 British weight 0.311" bullets; that's pretty much all a subsonic .300 AAC Blackout is.  In guns, there's no such thing as magic but you sometimes have to pick up an old musty reloading manual to find the potion recipes.

Up Gunning the SKS

A Yugo SKS with an as-issued fixed magazine repackaged into a bullpup stock configuration.

The main weakness of the SKS and it's AK-47 cousin versus the M-16 systems platform is perceived accuracy potential.  The accuracy potential is actually there but you have to make some changes to the packaging of the gun.  Several years ago, I experimented with this with an iron sight solution for the SKS and found out that the spring held rear sight is to blame for the SKS's meandering behavior reputation.  The rear sight can move as much as 6 to 8 MOA side-to-side randomly as the gun is fired. That is greater movement than the width of a standard bullseye.  It's literally pointing at a different place shot to shot.  Changing the sight system to a less jittery one reveals the rifle can hold between 1 to 2 MOA or about the same as a rack-grade M-1 Garand.  That should not be surprising given that both rifles are military designs from the same battlefield era.  The axiom that mission drives engineering remains intact.

Better sights do wonders for the SKS but until recently, getting an optical sight mounted on an SKS has been rather problematic.  Solid durable bases suitable for current generation rifle scopes that do not lose zero and still allow proper dis-assembly for maintenance had been missing from the market. This is now beginning to be addressed.  Firms like RPC in Texas have begun to market replacement receiver covers with Picatinny rails that tie solidly into the action. These solutions work well but they do raise sight height above bore line.  You should plan to put the SKS into an aftermarket stock designed to provide good cheek weld with an optic if you go this path.

Another firm that has tackled the systems solutions problem is Shernic Gun Works in Alhambra, CA with their Bullpup Stock solution.  The assembled SKS reminds one of a .30 caliber Tavor. The trigger linkage mechanism delivers similar feel to the original donor rifle. It allows for stripper clip loading which is great if you elect to keep the original 10-round military magazine. And it has a top rail for mounting pretty much any sight system you'd also care to mount.

Note the gun is now an inline barrel configuration similar to the M-16, Steyr AUG, FN 2000, FAMAS, Tavor, et al.  The trigger operates via a linkage connected to the orginal trigger.  Sighs are mounted around 2.75" above bore axis, same as the M-16 series system.  Rails allow use of a bipod creating a compact and stable firing solution.

The SKS sits snugly in the bullpup stock.  The scope rail top cover joins to the stock via eight mating screws.

The trigger linkage is ingenious and when properly adjusted feels pretty close to the original trigger which, while it doesn't come even close to what can be done with an AR-15, is still manageable enough to deliver good shots.
This particular Bullpup rifle has an SKS with a fixed 10 round magazine in it that can be fed by SKS stripper clips.  The stock cover removes with one pin then allowing removal of the SKS receiver cover and easy access to clean the barrel inserting brushes and patches from the breech.   Most of the other scope mounting designs are not as convenient for accomplishing field maintenance.

This gun installed in this stock is a Yugoslavian model.  They are more prone to gas leak short stroking than the simpler and more robust Chinese variant.  Replacing the gas cutoff plug helps as this part takes the brunt of the erosion coming out of the barrel hole.  Surplus guns have seen a lot of hot gas.  Greasing the piston grooves helps too.  The concept is much the same as lubricating the gas rings on an AR to help keep the seal to function the action. 

The Shernic product does have some quirks at this stage in its development.   The Picatinny rail on the top piece is comes out of a mold that, due to heat shinkage, is about 0.030" narrow of a military specification rail.   It's a bit loose which is not good for accuracy.  Fortunately 3/100th's of an inch is easily shimmed.   Shernic does have plans to build a new mold in the future that will produce mil-spec rails but currently recommends using a shim made from cut up plastic gift cards to establish firm contact for mounted optics.  I found three or four layers of masking tape work too at which point you've got a solid mount.   Because the stock's rail is made from plastic, I recommend using a 1/2" aluminum riser to build a more durable rail to attach the scope rings to.  You have to do it anyway because a riser is required with most in-line - meaning the barrel is in line with the shoulder - stock designs.

The Shernic design is a work in progress.  This image shows the use of layers of masking tape to build up material to make up for an 0.030" too thin top rail due to plastic shrinkage tolerances in the mold.  The company has made incremental improvements to the design in the past and says it plans to offer a replacement mil-spec rail top cover in the future. 

Optics: Let's go All the Way to a Ballistic Compensating Reticle

As I said earlier, the 7.62x39mm cartridge is the ballistic twin of rounds like the .30-30 Winchester and .300 AAC Blackout.   The numbers tell the story.  From zero to 600 yards, a modern ballistic compensating scope with an etched reticle for the .300 Blackout supersonic rounds will be within 1 MOA of point of aim; that's within 6 inches point of impact holding on the same aim point for either round out to 600 yards.

.300 AAC Blackout7.62x39 mm
RangeVelocity, fpsDrop, MOAVelocity, fpsDrop, MOA

It turns out there is such a scope available.  The people at Pride-Fowler Industries released a .300 Blackout 1.25-4X first-focal plane etched reticle optic just over a year ago that sells for about $350.00.  I'd taken a look at a 7.62/.5.56 NATO version of scopes from the same OEM factory source when they came out and mentioned I had this SKS Bullpup Tavor'ish thing I had put an old Weaver El Paso K3 with a post reticle on and was having fun with to John Pride.  He said "well that's really interesting" and then a package showed up with one of these PFI Blackout scopes in it with a hand written note saying "Give this a try and tell me if it works."

The Pride-Fowler RR-Evolution BLK mounted on the SKS.
And so off came the Weaver K3.  I digress to report it did not wind up in some junk box but instead went on a Lee-Enfield No.4 Mk1(T) sniper rifle clone to shoot a CMP Vintage Sniper match.   Back to the SKS,  When I first tested it I was disappointed in the performance.  I had attached the Weaver K3 using mounts that were narrower on their footing so they were solid with the Shernic stock's top rail but I used mil-spec Picatinny monts with the PFI scope.  That's how I discovered the undersized rail width and the need to shim later confirmed to me by Shernic Gun Works.

Left side view of the scope mounting showing the use of the 1/2" aluminum riser.  This raises the scope to the proper height for the eye with a straight line stock and provides a more durable metal versus plastic contact point to attach the rings.  In this photo, a PFI Combat Red Dot sight is also attached.  It's actually the most expensive thing in the photograph. :)
The scope works like other ammunition matched ballistic compensating such as the military's ACOG and RCO combat optics for the M-16 and PFI's RR-900 model for M-14 based Designated Marksman 7.62x51mm NATO and the PFI/US Optics collaboration 1-6X scope designed for the FN-SCAR also in 7.62x51mm NATO.  All of these scopes incorporate both target range estimation and ballistic holdover compensation into their etched glass reticles.  Most are based on the flight curve of NATO specification ammunition which is remarkably the same for both the 5.56x45mm and 7.62x51mm ammunition.  STANAG standards equals mission definition equals engineering performance remember?

The PFI BLK scope differs from the NATO spec scopes in that its etched ranging reticle traces the Soviet intermediate ammunition flight curve.  As far as I know, it's the only one available to the U.S. market that currently does.  That's significant because the 7.62x39mm and it's ballistic cousins represent a sizable under addressed market segment.  Just saying.

The PFI RR-Evolution BLK optic.  Notice it has both subsonic and supersonic range markers to the left and right of the vertical axis.   You use the supersonic marks with the 7.62x39mm Soviet round. 
Does it work?

You bet it does.  With the scope base now shimmed tight to the top piece,  I re-zeroed the scope for the 200 yard hack in the reticle on a 6"x 6" steel plate.  Then I leap frogged to a 12" x 12" target at 300 yards and refined the zero there while firing a checkpoint round now and then to affirm the 200 yard reticle mark still connected with its target.   Then out to another 16" x 20" plate at 600 yards holding on the 600 yard maker and making final elevation adjustments.   After that, firing sets of 200 --> 300 --> 600 shot sequences at will was easy as can be.

Give it a try.  The old SKS will surprise you with what it can do.

Note:  If you want to look them up,  Shernic Gun Works is at http://sgworks.com/  and  Pride-Fowler is at http://rapidreticle.com/

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