Modernizing the SKS part 3: in part 2, (11/10 issue), Coffield fabricated a rear magazine latch, installed a U.S.-made trigger and fitted the stock. This time he installs a spring-loaded firing pin and a recoil buffer to finish the SKS.
Sometimes these changes or modifications might be very minor as in adding a recoil pad or swapping out the sights. In other instances as we have so often seen here in. the pages of SGN, the modifications can be pretty drastic.
This SKS project is definitely a good example of a major modification. I had owned a cheap Chinese-made SKS for many years. It was an interesting rifle but I never really cared for it. The machine work was just too darn rough and crude and the stock looked like it was made from a pine two by four..;
It was definitely a gun designed to be used by a peasant army. Although I have to admit the darn things worked and worked well under some incredibly rough conditions.-I saw numbers of SKSs in Vietnam that had been carried by the Viet Cong and had seen some really rough use. No matter how rusted or beat up they were they still worked! Ultimately you have to admit that it was a darn good design for its intended use.
One of the major problems I had with my SKS was the use of an integral 10-shot magazine. To load the SKS you had to use a stripper clip. The magazine was not designed to be removed from the rifle. It was not like the detachable box magazine on the Ml6 or M14 rifle. You could never carry an additional loaded magazine to quickly insert when the original magazine in the gun was emptied.
Keep in mind that this idea of charging a fixed or semifixed magazine was not new to the SKS. The British Lee Enfield bolt action used the same basic concept. Yes, you could remove the 10-shot box magazine on the Enfield but soldiers were not trained to do so nor were they issued additional magazines. Instead, like the SKS, they were issued ammo in stripper or charger clips to refill the magazine while it was still in the gun.
Another example of the use of an integral magazine was the FN Model 1949. This was the predecessor of the FN FAL. Years ago I owned a FN Model 1949, and unlike my Chinese SKS, it was a beautifully made firearm. Later, when the FAL came out, the integral magazine of the Model 1949 was eliminated and a detachable magazine used instead.
And of course, the AK-47 that replaced the SKS also used detachable box magazines. The more you think about it, the more you wonder why anyone would want to use anything other than a detachable box magazine on a military rifle. It just never made sense to me. Consequently, I was never really happy with my old SKS and seldom took it from the gun safe to use. It just lived a lonely and neglected existence at the back of the pile.
Evidently I wasn't the only one who disliked the integral magazine. Not too long after the SKS made its appearance a commercial detachable magazine was developed and sold. Basically this magazine replaced the original integral magazine. It employed a projection on the front of the magazine box that hooks into the stock. It works but it's awkward to carry and use and I just never cared for it. The front projection was always getting in the way. It definitely wasn't user friendly.
I wanted to use the AK-47 magazine. Those magazines are designed for the 7.62x39mm cartridge, readily available, tough, durable, and inexpensive. The problem was I wasn't quite sure how to adapt the SKS to take 'em.
Well over a year ago, I happened to run across a little booklet at a local gun show that showed how someone had done this. It looked interesting and I bought it. Later as I did more research on the conversion I learned the procedure described by the unknown author of my booklet could get you into a lot of trouble with Federal law enforcement and the BATE
What the author didn't tell you was that by converting the SKS to take an AK-47 magazine you were produc ing a firearm that was banned from importation and was therefore breaking the law! The things folks don't tell you can get you in a whole lot of hot water.
Fortunately I contacted the BATF and got some great help in the form of very detailed instructions on what I would have to do to avoid breaking the law. The BATF requires that a specific number of parts used in the modified firearm must be made in the U.S. In the case of this project, I had to use at least four U.S. made parts from a list of 14 components of the SKS. The other 10 parts could be foreign made or original SKS components.
This was relatively easy to do. In fact, I ended up using more U.S.-made parts than the minimum required. All of these U.S. made parts were commercially available and most of which I ordered from Brownells. I actually ended up using six U.S.-made parts; the gas piston, trigger, hammer, sear, buttstock, and handguard. That was technically more than needed but it's always better in a situation like this to do too much rather than not enough and end up in a very bad place!
In the previous parts of this series I modified the receiver to accept the AK-47 magazine. This entailed opening up the receiver and cutting away part of the feed rails. I also installed a front magazine seat and modified the original SKS mag latch to fit the AK-47 magazine. The trigger housing was also shortened and the Choate stock opened up to allow insertion of the larger AK magazine. Finally, the bottom portion of the bolt was narrowed a bit to allow it to pass between the lips of the AK maga-zine when feeding rounds into the chamber.
The next major portion of the project was the installation of a new firing pin and firing pin return spring. While it's not required by the BATF for the magazine conversion, I wanted to do this for safety reasons. My Chinese SKS had a floating, non-spring loaded firing pin. It just floated around inside the bolt.
The problem with this shows up when the bolt slams forward against a loaded round in the chamber. Inertia causes the firing pin to move forward until it's stopped by the primer! Yeah, it actually hits the primer and that's the problem. Under some conditions, the impact from the firing pin can actually ignite the primer and fire the cartridge. This is the classic slam fire.
By the way, if you have a chance to fire an SKS you might want to look at this firsthand. Load just two rounds and fire one round as normal. Now after the gun has automatically chambered the second round, open the bolt and eject the unfired round. Put the rifle aside and examine the ejected unfired round. I would be willing to bet you'll find an indent on the primer from the tip of the firing pin.
As I understand, the original early production Russian SKSs made prior to 1950 used a spring-loaded firing pin to prevent this. However this feature was omitted in later production Russian and European guns as well as Chinese-produced SKSs. My guess is that this was not a significant problem when the SKS was used by the Chinese or Russian military because they use relatively hard primers. That can change here in U.S. with commercial or handloaded ammo. The commercial primers can be quite sensitive compared to the military primers and this can possibly lead to a slam fire.
It's also interesting to note that the original military firing pin has a tapered shape that matches the tapered hole inside the bolt. The problem with this is that with the addition of some grease, crud, dirt, or carbon fouling the firing pin could possibly stick in the forward position! Again, that could lead to a slam fire which is definitely not a good thing.
To deal with these issues, I opted to install a Murray's spring loaded SKS firing pin. Murray Gunsmithing, 12696 FM 2127, Bowie, TX 76230, telephone 940-928-0002, www.murraysguns.com offers these pins for $39 each, including two return springs. He also has a number of other products including U.S.-made SKS hammers, sears, and triggers. If you're thinking about modifying your SKS in any way, you really should check out the Murray Gunsmithing web site.
The Murray firing pin is made of 420 stainless steel and is quite, a bit lighter than the original military firing pin. Using my old Lyman powder scale, I found the Murray firing pin weighed only 107.8 grains, while my original Chinese firing pin weighed in at 130.4 grains. That's quite a bit more and this alone may explain part of the reason for the dimpling of the primer on the unfired round.
The heavier firing pin has considerably more energy as the bolt slams forward and thus the firing pin can have a more significant impact on the surface of the primer. It can have enough of an impact under some circumstances to possibly cause the primer to ignite.
The Murray firing pin also has a very distinct and different shape than the Chinese pin. There is significantly more clearance on the firing pin body to allow for any foreign matter that might get inside the firing pin hole in the bolt. This can help prevent the firing pin sticking or jamming forward with the tip protruding through the bolt face. Also, the rear of the pin has a shoulder to stop forward movement. As received, the firing pin tip protrusion was right at.051" which is very appropriate for this rifle. The Chinese pin, by the way, had a bolt face protru-sion of 055.
The installation was simplicity itself. You just drive out the firing pin retaining pin, remove the Chinese firing pin, install the Murray firing pin and spring and then replace the retaining pin. Nothing could be simpler or easier! Of course, you'll want to check to make sure the new firing pin moves easily back and forth and that the return spring is properly engaged. All in all, there was not much to it, and it was a great way to upgrade a critical component of the SKS.
With the firing pin taken care of, the next step was to do a little cosmetic work. Because I used the Choate stock, there was no longer any opening in the forearm for either a bayonet or cleaning rod. Quite frankly, I saw no need for either of these items on this conversion. While I could have just left those components off, I would still have had the base for the bayonet and the seat for the cleaning rod on the barrel, and that just looked out of place.
It was a simple matter to cut off most of the extraneous material with a hacksaw and then finish contouring or shaping with a file. When doing this you'll end up shortening the rear attaching pin. Be. careful that you don't file away so much material that you cut into the body of this pin.
After the base was shaped and polished, I used Brownells T-4 cold blue to blacken the exposed metal. This cold blue was a good match for the original black metal finish and went on very easily. I also took the time to touch up the exposed metal inside the receiver where it had been opened up for the AK-47 magazine. While you could leave the metal bare, it just looks better and more professional to have it blackened. This also applies to the forward magazine seat.
The final modification was the installation in the top cover of a Buffer Technologies recoil buffer. The idea behind this buffer is to help reduce the force of the impact of the bolt carrier as it slams into the rear of the receiver. I'll be the first to admit that I'm not 100% sure just how much good this buffer will do over the long haul, but I'm willing to give it a shot.
The only concern I have is its durability. According to the manufacturer, the buffer should be good for at least 5,000 rounds or more before it'll need to be replaced. I seriously doubt I'll fire anywhere near that many rounds in this SKS. But I still have questions as to the effect time and the repeated battering from the bolt carrier will have on its life span. Frankly, I don't know, so this will be as much a test as anything.
The Choate stock is nicely made and fit well. Due to manufacturing variations on the many different SKSs that have been brought into the USA, there is always a possibility a particular gun will not fit the stock perfectly. Choate recognizes this and addressed that issue in the instructions provided with the stock. In my case, there was a slight gap between the rear of the recoil shoulder and the stock. While Choate had supplied a synthetic spacer to fill this gap, I opted to make my own steel spacer. I figured it would be more durable and would more effectively transfer the recoil forces to; the stock.
My spacer was nothing more than a piece of steel sheet that measured 11/2 inches by 5/8" by about.061" thick. I made it wide enough so it was held firmly in place by the sides of the stock opening around the recoil lug. Because there is absolutely no place for the spacer to work loose and go once the stock and action are assembled, you really don't have to even glue or attach the spacer to the stock although that would be a darn good idea.
Once the spacer was completed and installed, I assembled my newly modified SKS. There were a few places were I needed to do just a bit more fitting. I had to remove just a bit of metal from the sides of the bolt where it was rubbing against the magazine lips. I also filed off a few thousandths from either side of the rear hook on my magazines to provide just a bit more clearance with my modified magazine latch. All in all, these were very minor issues.
Speaking of spacers, one of the really nice features of the Choate stock is the fact that you can alter the length of pull. The stock comes with two 1/2" spacers you can remove or leave in place between the recoil pad and the stock. I like my stocks to be a bit on the long side so I left both of my spacers in place for a length of pull of 14 1/2 inches. By the way, if you hear something rattling around in the stock, it's the extra screws Choate supplies for attaching the recoil pad and spacers.
The Choate stock also includes a detachable cheekpiece. The cheekpiece is normally needed only if you mount a scope on the SKS. If you leave it in place and only use the iron sights as I did, you may find that the comb is a bit too high. With the Choate stock and the other work that was done, the old SKS definitely had a new look. In a way, it looked a lot like a smaller version of the Russian 7.62mm SVD Dragunov sniper rifle. I kinda liked it! There was one aspect of this conversion that I did not care for and had not anticipated. I no longer had a bolt hold open function after the last shot was fired. Because of this, I have to keep track of my rounds as I'm shooting if I don't want to try to fire with an empty chamber. I don't like that but I can live with it.
With the rifle assembled, I once again checked functioning and feeding using some Brownell 7.62x39mm action proving dummies. There were no surprises; it fed: flawlessly from both of my AK-47 magazines. With that completed, I needed to head to the range for test firing.
At 50 yards, using some military ammo of unknown background, my SKS would give me a five-shot group of about 3 inches when fired from a bench rest. Out at 100 yards, the five-shot groups opened up to close to 6 inches. While it's not great, realistically it's not all that bad for an iron-sighted gun with questionable ammo that was loaded back in 1963!
As for the functioning of the AK-47 magazines, they all worked just great in the SKS. During my test firing I did not have a single failure to feed. The magazines locked up securely and fed flawlessly. The only problem I had were several rounds that failed to fire but I attribute that to the fact that the ammo was so darn old.
This was an interesting project and it allowed me to finally do something with a gun I never really liked all that much. This project also pointed out the importance ot doing research relating to the legality ot any modification you might make and especially so when dealing with an imported firearm. Never rely solely on what you see or' hear at a gun show or what your buddy might tell you. If there's any question about what you can and can not do legally, contact the BATF for specific, factual information. You can never be too careful about this and ultimately only you will bear the legal responsibility for any violation of the law. That's definitely the most important point to be learned from this exercise.
The next time we get together I'll start on a very interesting and unusual Mauser carbine project.
Until then, good luck and good gunsmithing!
SGN GUNSMITHING PROJECTS
Want to read even more about home gun building? Get Shotgun News Gunsmithing Projects, a 448-page compendium of a decade's worth of gunsmithing stories from Reid Goffield, Steven Matthews and other SGN writes. Whether the project is restoring a doublebarrel or building a semi-auto Bren gun, you can read about the skills, tools and materials you'll need to make it a gun you'll be proud of!
Visit: www.shotgunnews.com or call (800) 260-6397
In Part.2, (11/10 issue), Coffield fabricated a rear magazine latch, installed a U.S. made trigger and fitted the stock. This time he installs a spring loaded firing pin and a recoil buffer to finish the SKS. By Reid Coffield
|Printer friendly Cite/link Email Feedback|
|Date:||Dec 10, 2011|
|Previous Article:||Mil dot mania: they've become essential for military snipers, but what do these complicated reticles offer for the civilian shooter?|
|Next Article:||Ask the gunsmith: stones for sears.|