ARS NOTES
AK. MISC.
(updated 10-06-2009)
Page Outline |
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Side-Mount Scope Rail | |
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There are several types of side-mount scope rails. Some share the center support rivet, some share one of the rear trunion rivets. I prefer this Russian (Belarus) one because it shares no rivets. It is the easiest to mount on an already-built receiver. Leapers (UTG) makes a clone that is actually nicer machined than the original Russia. |
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For repeatability, I made a marking fixture from a piece of angle iron, but you can do the same with a note-card or thick paper. I had to weld in and re-drill my front hole when I discovered that the three holes are not in line with each other - the forward one is 1.5mm higher. |
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The top edge of the rail should be approximately 10.5mm below the top edge of the receiver. It is important that it be parallel and and provide adequate clearance for the heads of the trigger and hammer axle pins. If you want to be really anal, you can align off the bore instead of the receiver, but most ComBloc optics have enough adjustments for the minor variations in front trunion and receiver angle. Using the rear most hole as "0", the middle hole is 30.8mm, and front hole is 75.8mm AND 1.5mm higher. |
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To insure the receiver lays flat on the bottom of the mill vise, I use a flat plate with holes drilled to clear the rivets. |
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While it is easiest to put the scope rail on before mounting the barrel, you can do it afterwards with adequate barrel support. |
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This image shows how I hold the receiver in the mill vise for drilling. Because the NDS receiver is hard, a regular drill tends to walk. I use a 1/8" 2-flute chisel point center drill to start the hole and then I can finish it manually with a 5/32" cobalt bit. |
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I use the pneumatic squeeze to install the rivets, with a flat inside piece, and an outside form turned to fit inside the scope rail recess. I put the rivets in a hand drill and spin them against a belt sander to match head profile to the recess in the rail. |
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I prefer the ease of installing the FAL -type trigger and hammer axle pin retaining plate instead of the traditional wire shepherd's hook. Unfortunately, the rear scope rail rivet interferes with the plate. Shown is an original and a plate unable to clear the rivet. |
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using a smaller rivet in back, I could flex the plate over the rivet, but it would still make the selector lever a little tight. |
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the small clearance cut I made on the retaining plate. |
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installed, it clears the rivet |
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Once I had my first plate modified, it was easy to clamp a bunch together and cut them all at once.
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Selector Markings | |
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Most of the NDS receivers do not come with selector markings, and even in those cases when the workload at NoDak Spud allows for custom markings, they do not include the detents. You can put both the full-auto and semi-auto positions on for authenticity, as the rifle will fire semiauto from both. First, install a selector and make a rub mark on the receiver showing the curved selector path. |
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Place the selector stop plate on the receiver to mark the point of lowest travel. I use a scrap selector with the detent drilled out so I can mark it. |
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draw a line through the bottom position, and a second parallel line 10mm higher. Draw two vertical lines 3.5mm apart so that the two positions are equidistant from the edges. |
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On some models, the lines correspond with the selector angle, but this requires more complex fixturing of the receiver. There are many other variations where the two grooves are parallel with the top of the receiver, and thats what I use. This is a 3/32" carbide ball end mill about .007" (0.18mm) deep. |
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finished grooves for the selector detent. |
Pistol Grip Plate | |
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When fired with the stock folded, greater force is applied to the receiver under the pistol grip. Some models using a folding stock have the receiver reinforced in this area with a spot-welded plate. |
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The plates I have used do not come with the 5 holes for spot-welding, so they will have to be drilled. The small hole matches the alignment hole on the bottom of an NDS receiver and is useful for obtaining the proper alignment. |
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I use a copper backing plate on the inside of the receiver and keep the amperage relatively low - around 60-65, so I don't burn through when TIG welding. Here is the plate installed.
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Triangle Side-Folding Stock Rear Trunion | |
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There are some differences for installing the rear trunion on a triangle side-folding stock model than on a standard fixed stock. Two of the rivets are flat to clear the stock weld when folded, and as the top rear rivet is very close to the hinge, you will need to bevel the end of the receiver clamp (or make a second one) to clear it. Also, the bottom support plate will have recesses for the flat rivet heads. REMEMBER - the front trunion has a hole in it for the latch axle - if using a standard front trunion, you should drill this hole through it before installing the barrel. It is a lot more difficult to drill the hole afterwards, and there is a risk of drilling into the barrel. |
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procedure is the same, even with the slightly different parts. First insert the alignment pin, then tighten the clamp to keep the receiver from shifting. You want it a little less tight than normal so the clamping screw doesn't mar the receiver - the top support plate cannot be used because of the hinge. |
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Insert the flat ram and partially compress the rivet. You must either shorten the rivet before hand, or make them round-head and mill/file the rivet flat afterwards. I removed from fixture so you can see - leave in the fixture if possible to insure maintaining proper alignment. |
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finish compression with either a flat form or a round form, depending on whether you are going to file the head afterwards. If you are only doing one, it is probably more time efficient to make the rivets standard round head and file afterwards, as it takes some practice to calculate how much to shorten the rivet to get a head symmetrical to the other side |
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finished rivets |
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closeup of bottom support plate |
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closeup showing why the clamping screw has to be beveled to clear hinge |
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here you see the clearances milled on the weld for the flat rivet heads. You also can see the receiver sticks out slightly past the hinge. This small flange will bind on the top part of the stock hinge and has to be trimmed. |
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Another view of the area needing trimming. |
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I use the side of a small rotary cut-off wheel and finish with a file. |
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this gap is typical of an NDS-2KP receiver. You haven't done anything wrong, and I don't have a cure for it. It is because the rake, or angle of the receiver fold is off from normal by around 1/2 degree - it doesn't show with a standard stock, but it does with a folder.
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Triangle Side-Folding Stock Installation | |
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here are some tools I made made to ease the assembly of the stock springs. The spring squeezer is a cheap pair of needle-nose pliers with washers welded to the end. The pry tool is a small nail puller with the inside opened up to clear the spring guide. The third from right is a small screwdriver notched as a spring catcher, and the last is small hook |
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using a screw driver or piece of scrap round stock as a guide, compress the spring |
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insert the spring into the receiver and capture it with a pin or screwdriver. |
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pry the spring away from the left side of the receiver and drop in the retaining pin. |
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This is a small wrench I use to hold the spring - it should be slightly smaller than the spring so that it holds by tension |
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insert from front and capture with pin or small screwdriver |
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use modified screwdriver to push the levering part of the spring back and hold it there |
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insert stock catch. the parts should remain in place by friction withdraw your slave pin and exchange for the button-head retaining pin. |
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withdraw the spring pusher and use the hook to pull against the spring tension on the pin so you can push it all the way in. The groove on the pin may not catch on the arm of the spring that retains it, so you may need to hold it in place and pry the spring arm into the groove.
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