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SKS optic mount: scoping a SKS carbine can be a worthwhile gunsmithing project.

Not every old military rifle is readily adaptable to scope mounting but a little ingenuity will get the job done on quite a few of them. So it is with the SKS carbine. The Samozaryadnyj Karabin sistemy Simonova (Self-loading Carbine, Simonov system) is a Soviet semi-automatic carbine designed in 1944 and chambered for the 7.62 x 39mm cartridge. It was quickly surpassed by the AK-47 but continues to see service and became a popular surplus export in the civilian market.

An avid hunter presented me with his SKS carbine, typically used with open sights, with thoughts of having a scope mounted for deer hunting. He really didn't want to put a lot of money into the gun so some serious improvising would be in order. With the removal of a small strip of stock wood to expose additional receiver surface and the addition of a spacer between mount and receiver, a very attractive and sturdy mounting job was possible. I used a side mount I had on hand, which had a one-piece integral Weaver base attached. This mount base was for a Model 1100 Remington shotgun. Standard Weaver quick-detachable rings fit this base.

The basic tools needed include a drill press or electric drill, #18 and #29 drill bits, an 8-32 tap, small rasp, fine-tooth hacksaw, flat file, machinist's rule, a screwdriver and Allen wrench. The only materials required are two 8-32 x l/2-inch socket-head screws, two 1/2-inch number 8 round-head sheet metal screws, and a length of flat metal stock 9/16 x 3/16 x 4 3/8 inches in length. This piece of metal is used as a spacer between the side mount and the flat surface at the side of the receiver to hold the base flush with the gun stock.

Checking Scope Fit

Before removing the action from the stock, attach the scope and rings to the base and carefully lay the mount exactly in position where it will later be permanently mounted. The scope is checked for sufficient clearance for clear viewing and that the objective lens clears the lowered rear sight. It is also important to check that the bottom of the extended scope base is positioned approximately 1 1/4 inches above the lower portion of the cartridge ejection port. This clearance will permit ample room for cartridge ejection.

If the center of the mount flange is positioned about three inches from the rear of the receiver, screw application will be very workable and optimal scope eye relief will be attained. With the mount placed and held where you want it, carefully mark the outer borders of the mount on the side of the stock.

As the photos show, approximately 3/16 inches of wood will later be cut out at the top left side of the stock to square things up and expose a bit more receiver metal for a very rigid mounting. But first, with the scope base aligned and held temporarily in position, carefully mark the screw-hole positions so the through-holes will be located as required on the side of the receiver. Ideally, the tapped holes should be located 1/4 inches below the square surface of the top of the receiver. It's ideal if the rear screw hole is centered 1 3/8 inches forward of this hole. There is some margin for variation in screw-hole location, but not much, as you will later see as you look inside the receiver. The gun can now be disassembled.

Field stripping the action and removing the action from the stock on the SKS carbine is simple. Just lower the trigger assembly by depressing the lock located at the rear of the trigger guard and pull downward on the trigger guard. With the trigger assembly removed, pull down on the magazine assembly and remove it as it pivots out of the front cam-lock position. The barreled action is now floating in the stock and can be removed.

Removing the bolt assembly is accomplished by lifting and pulling outward on the receiver cap lock pin located at the very rear right side of the receiver. The receiver cap, which covers the bolt thrust spring and plunger, is then slid off for removal of the bolt and spring assembly. The inner receiver is now exposed and free of parts and can be worked on. Assembly is just the reverse of take down and takes but a minute once you've done it.

The spacer used as an interface between the scope mount flange and the receiver should be made now. Cut a piece of 3/8-inch-thick aluminum or steel to a width of 7/16 inches and to a length of 4 3/8 inches. After the spacer is rough cut, mill or file the piece to uniform dimensions.

The spacer can now be mortised into the stock so the upper surface of the spacer is exactly flush with the top of the receiver. This can be checked by laying the spacer at the side of the stock with the barreled action in place and sighting along the top of the receiver rail. Then, carefully remove enough stock wood to fit the spacer so it lies correctly in place with its upper surface at the same height as the receiver rail. With the spacer in position, I used a small C-clamp to hold it in place and drilled the holes through the spacer to a depth sufficient to just mark the receiver metal to indicate screw hole position. Here I used a #29 drill and later enlarged the spacer holes to a size 18 body drill to fit the 8-32 screws for mounting.

Drilling and tapping the receiver should be done with care. While the receiver does not appear to be case hardened, it is made of fairly hard metal. Care should be exercised to drill and tap slowly to avoid breaking a drill or tap. Use a good quality, sharp drill and tap with proper lubricant. The receiver wall is fully 0.110-inch thick where it is tapped, providing sufficient screw thread depth for hardened socket-head screws. I started with screws a bit over length as the mount and spacer were tightened in position and later cut the screws to exact length.

Having drilled and taped the mount and receiver holes, clean the inside of the receiver and replace the barreled action in the stock. Do not replace the bolt and receiver cap yet as you'll want to check how the scope base and spacer fit. Tighten the screws with enough torque to see they don't protrude further than flush with the inside of the receiver wall. Screws should be fitted to exact length.

With the scope base attached, a look inside the open receiver shows a perfect place where two additional sheet metal screws can be effectively used to hold the scope base flange to the stock. A close look at the side mount shows the two holes normally used to attach this base to a Remington Model 1100 shotgun. The smaller (front) of these two holes is ideally located to place a 1/2-inch number 8 metal screw into the stock wood. Then, exactly 113/16 inches forward of this existing hole, drill another hole through the base flange using the #18 drill for the second metal screw. As a lead hole into the wood, use a #29 or #30 drill for a perfect screw fit.


Though the recoil on this little rifle is light, the addition of two extra screws into the stock wood really provides a solid mount and it looks good. I would advise the use of a thread-bonding material on the two socket-head screws on final application of the mount. The scope mounts perfectly over the bore line to enhance the aesthetic appearance of the gun.

The SKS is well made with few shortcuts in workmanship. Scoped, this little rifle can provide a lot of sporting and recreational shooting pleasure at low cost.
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Title Annotation:BENCHWORK
Author:Johnson, Norman E.
Publication:American Gunsmith
Date:Feb 1, 2016
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