Yooper John's SKS - Battle rifle of many nations

The following is an article that was reprinted with permission from  GONZOSKS1 from Survivor's SKS Boards................THANKS!!

. Differences evident in SKS-M rifles . . ... as compared to the regular SKS.

I REALLY like the SKS-M model. It has all the things I love about the regular SKS, plus cheap full capacity magazine availability. Dressed in the Monte-Carlo stock and sporting 5 round mags (converted to hold 10 rounds by installation of the TAPCO followers), they are handsome guns and don't have quite the "evil" look at the range as, for example, an AK variant might have.

I thought it might be informational if I posted all of the "differences" I've notice as compared to a regular Norinco SKS. I may update this post with pictures once I get a new digital camera to replace the one I no longer own. (Have I mentioned that divorce sucks?)

This post speaks only to the rifle commonly known as the "SKS-M" model, which is the post-89 import approved version. Its found with both a nice monte-carlo stock and (generally regarded as lame) wood thumbhole stock. I've never owned (or fondled) an SKS-D and I understand they handled some things differently, so that variety isn't addressed here.

General Specs:

Before getting into the "differences" and enhancements, lets talk general specs. The SKS-M rifle is of Chinese origin, and sports a 16" barrel. Its claim to fame, of course, is that it has the ability to accept standard AK-47 magazines. It does not have a bayo lug, but only a "nub" with a spring loaded mechanism inside where the lug would normally be. This allows retention of a cleaning rod, a function ordinarily provided by the bayonet itself. All SKS-Ms that I've seen utilize "stamped" trigger groups and pinned barrels. I've seen these stamped "SKS-M" or "SKS SPORTER" or just "SKS" on the receiver. The serial number is usually prefixed by a two figure manufacture year indicator. Generally, the receiver, bolt, and carrier are serialized to match. The trigger groups on these do not have serial numbers. In the rifles I've seen, nor do the gas pistons or tubes. The monte carlo style stocks are generally "blonde" with middlish to sloppy application of the finish. The thumbhole versions are blonde as well, and can be found with and without "grip tape." Like most Chinese SKS rifles, the wood is softer than most would prefer. Thumbhole variants have been seen with both "wide" and "narrow" handgrip areas. The mag well is lined with a steel liner secured by two screws through the side and one screw into the wood at the front. The front of the mag well liner is steeply angled, and one is best advised to duplicate this angle on insertion of the front of the mag to ensure quick and reliable mag changes. Neither of the "stock" SKS-M stocks will accommodate a Norinco "drum" magazine without grinding/inletting.

Now, onto the differences as compared to "regular" SKS variants. We'll go by categories:

1) Receiver:

a) Magwell. The most significant change to the receiver is that it is extensively machined to allow the AK-mags to fit. The machining occurs on receiver walls, up through one of the bolt rails (looking down from the top, you'll see a semicircular "cut out" on the right one of these). There is also some machining at the area under where the barrel meets the receiver. This "recess" is to allow the front of the mag to latch in. The machining is very extensive and in my view is the reason (other than the serious legality issues) that one should always be skeptical of "homemade" versions of an AK-mag capable SKS.

b) No bolt hold open. On the SKS-M's, the pillar just to the rear of the magwell doesn't even have the channel for the bolt hold open mechanism. For obvious reasons.

c) Pillar not machined to accept regular mag In a related distinction, the pillar behind the mag well is not machined to accept a regular SKS magazine. It won't fit without substantial grinding on the magazine or receiver.

d) Trigger housing attachment pillar. As discussed below, the trigger group pin (the one that holds the front of the group in place) is located differently on the -M variant. As such, on the pillar to which it attaches, the cut outs for the pin are not as deep. A standard SKS trigger group simply will not fit unless it is reconfigured with the pin at the "new" location.

2) Barrel Assembly/Gas System

a) Mag attachment point ground off of rear sight. This is self explanatory. Since a regular SKS mag would not fit in one of these, they've ground off the little "lip" under the rear sight.

b) Shortened gas system. A major difference. The SKS-M has a gas tube significantly shorter than the regular SKS. Apparently this was done due to the shorter distance between the gas block and the end of the barrel. In operation, that shorter distance changes the kind of impulse that goes into the system. In shortening the gas tube and piston, they allow more "barrel" travel time for the bullet after the gas block, which should help reliability. On the other hand, the piston now has a shorter "throw" before it bottoms out in the tube, which is probably addressed by the next item.

c) Larger Gas Port Hole If you look at one of these closely, the size of the gas port is much larger than on a regular SKS. I would guess this is to deal with the shorter impulse time and shorter throw of the piston. Bottom line: its dumping a lot more gas into the system for a shorter period of time. Mine have always functioned reliably, except when I've tried to add a recoil buffer. My theory is that the changes to the gas system seriously increase the velocity of the bolt carrier and bolt, and that with a recoil buffer the carrier rebounds forward so fast as to cause feed issues. I know a number of folks who have had problems with buffers on -M variants.

d) Barrel Length As noted above, these have 16" barrels.

e) Bayo Lug As noted above, its modified to simply hold the cleaning rod and cannot accept a bayo.

3) Trigger Group

a) Location of Front Pin Because of the where they have to weld on material for the AK-mag catch and because of the length of most back catch areas on the mags themselves, the front pin on the trigger group (the one that sticks out on the sides and holds the group to the receiver) is located further back on the group.

b) overall length The SKS-M trigger group has a shorter overall length from the back of the tang to the front of the mechanism.

c) Mag Catch Well, duh. The SKS-M has an AK-style mag catch and mounting area added. The Mounting area appears to be welded onto the front of the group during the conversion. The mag catch itself has two circular cuts hear the top so that when it pivots back it does not hit the cross-pin. A piece of metal replaces the original mag latch, and serves as the rebound point for the sear spring. The AK-mag catch is riveted in, and for this reason, trigger jobs on SKS-M rifles are more difficult. (Its also a pain in the backside to get the STIFF STIFF STIFF) mag catch spring back in place).

d) Different Trigger This is one not many people notice. The trigger on an SKS-M is angled differently as it sticks down through the trigger guard. As compared to other variants, the "at rest" position is much further to the rear. This helps with accuracy, as there is less over travel. As far as other reasons for this difference, I have my suspicions but am not really sure.

4) Bolt and Carrier

1) No Stripper Clip Guide Since the AK mags cannot function with a bolt hold open (even regular AKs don't have one), the stripper clip guide area on the bolt carrier is non-existent on an SKS-M. SKS-M owners should get used to the "bang bang bang, click" syndrome, just like AK owners.

2) Bolt Machined to accommodate AK Mags. Most people know this one. The two edges below the bolt rail slots on the bolt are machined away to allow the bolt to travel forward without interference from the magazine. The underside of the bolt is ALSO machined away in part, so as to allow the bolt to tilt down into battery without impacting either the magazine or causing stoppage when attempting to pivot down against a fully loaded mag. (If the bolt weren't so machined, it would "bottom out" against the rounds in a fully loaded mag -- i.e., the rounds would be pushed all the way down with no more room to go -- before the bolt went into battery).

3) Extractor Surface Rounded The lower portion of the face of the extractor is rounded off on every SKS-M I've seen. The reason for this is that if its not rounded off, the edge of the cartridges tend to hang up as the bolt strips rounds from the right side of the mag.


Well, that's what I've come up with so far. Let me know if this was helpful.