Receiver

I he receiver, or body, of the gun I should be built first because all I other parts and components are I attached to it or fit inside it.

^^ Cut to length (9 1/2 inches) and square both ends of the 1 1/4-inch OD seamless tubing. Determine which end the barrel will fit into; this will be hereafter referred to as the forward end. Three-eighths inch back from the front face, locate and drill four 1/4-inch holes that are spaced at intervals of 90 degrees around the diameter.

Slip a bushing, 1 1/8 inches long, snugly into the front receiver body to a depth of 5/8 inch. This leaves 1/2 inch exposed. Weld shut the four holes previously drilled, securing the bushing in place. The welds are preferably done with a TIG welder, sometimes referred to as "heli-arc." These should be built up above the receiver's surface and dressed back flush with the surface of the metal. Properly done, these welds will be undetectable when the gun is finished-

Now bore or ream the bushing to an inside diameter (ID) of .875, to accept the barrel shank.

Turn the exposed 1/2-inch portion to a diameter of 1 1/16 inches (1.065) and thread it 24 threads per inch.

Locate a centerline along the top of the receiver, with another centerline on the exact bottom side, 180 degrees apart. Lay out still another line on the right side 45 degrees below the top line, or in a nine o'clock position when viewed from the rear. These lines can be located and marked easily by mounting a cutting tool with a sharp conical point ground on it in the lathe tool post, exactly on the centerline. The point is drawn up against the work and drawn lengthwise along it, with the lathe carriage being cranked by hand. After the line is marked, rotate the work 180 degrees and repeat the procedure. Then do it once more for the third line. This will result in very straight and accurate lines, especially if the headstock is locked, or fixed, in place while the carriage is moved along the work.

The extreme front ends of both the ejection port and the magazine opening will be 1 1/4 inches rearward from the front face of the receiver (since the barrel bushing is now welded in place,

250" O.D. seamless 4130 Tubing .065 wall thickness.

1.065"

1.065"

-JCH

.625"

Bottom Side

Sten Mk3 Receiver Template
Upper receiver.

250"

.125 slot .200" deep for Barrel locating Pin

4"

Upper receiver, right side.

its front face will now be considered the front face of the receiver). From this point, on the right side measure to the rear another 1 1/4 inches. This is the rear edge of the ejection port. Then, 3/8 inch to the right of the top centerline, scribe a longitudinal line between these two vertical lines. Next, scribe another 3/4 inch below this line. This forms an outline of the ejection port.

Lay out another opening beginning 1 1/4 inches behind the receiver face and centered over the bottom centerline. If a Sten magazine is used, this opening should be 1 1/2 inches long and 7/8 inch wide (7/161, on each side of the centerline). The corners of this opening should be cut square, without any radius. Material inside these outlines can now be removed, with the milling machine, the hand grinder, or the interconnecting holes method described in Vol. I.

Lay out the cocking-lever slot and cut in the same fashion. Form the slot, 1/4 inch wide by 3 inches long, and enlarge it to 3/8 inch in diame ter at the extreme rear to permit installation or removal of the cocking lever.

Cut an opening to clear the hammer and disconnector in the same fashion along the bottom centerline and to the dimensions shown in the drawings.

Cut two small blocks from some type of steel that will not air harden when it is welded. You can use 1018, 4140, or similar for this The block used to form the front hinge bracket is cut 1/2 by 1/2 by 1/4 inch. Weld this to the receiver on the bottom centerline and just behind the threaded portion. The other block, which is welded in place at the lower rear of the receiver as shown in rhe drawing, is cut 1/2 by 1/2 by 1/2 inch. The edges of these blocks that join the receiver should be beveled to allow proper "filling" with welding wire or rod. The welds should be filed, or milled, back square and flat. This is probably unnecessary, but it looks better, so take a few minutes and do it, even if it doesn't show.

Drilling Upper Receivers

Left: Drill the upper receiver to allow for welding the barrel bushing in place.

Below: Barrel bushing, ready to be installed and welded.

Lower Receiver Milling MachineInch Threaded Bushing

Above: Dress the welds flush with surface. They are undetectable if properly done.

Right: Thread the barrel bushing to mate with barrel retaining nut.

Above: Dress the welds flush with surface. They are undetectable if properly done.

Right: Thread the barrel bushing to mate with barrel retaining nut.

Handgun Milling Milled Pistol Mill

Above: Weld ihe block to the lower side to form the hinge hanger. Weld a similar block at rear to accept the grip bolt.

Right: Openings in receiver are easily cut with milling machine.

Below: It will take a little longer, but the same result can be accomplished using a hand grinder.

Lower Receiver Milling MachineHomemade Receiver 9mm

Left: Cut a slot to accept the barrel locating pin in the receiver using I/8-inch end mill.

Below: Drill a hole for barrel locating pin through the slot, assuring alignment.

Left: Cut a slot to accept the barrel locating pin in the receiver using I/8-inch end mill.

Below: Drill a hole for barrel locating pin through the slot, assuring alignment.

Tool Install Locating Pin Bulk Head

CHAPTER

m Mm

I he bolt, or breechblock as some I insist on calling it, is made from 1 I 1/8-inch-diameter round stock, 6 I inches long. To prevent battering and undue wear, it should be made from material that can be hardened. If commercial steel is available, buy a type that you (or someone with the facilities) can harden to between 35 and 40 on the Rockwell "C" scale. If none is available, automobile axle material will serve admiiably. It will almost always require annealing, as described in Chapter 2, because most of these have an extremely hard exterior surrounding a softer inner core.

Although this book is supposed to describe how to build a submachine gun, I will show two different bolt and trigger assemblies. One will deal with an open-bolt, full-automatic design; the other is a closed-bolt, hammer-fired weapon. The latter is harder to make into a full-automatic weapon.

Whichever configuration you desire, they are made in the same manner and can actually be converted by switching the bolt and trigger assemblies. Be warned again. Don't let the feds catch you with the open bolt and corresponding trigger assembly, even if you don't have the rest of the gun.

At any rate, chuck a suitable piece of material in the lathe with the ends squared and true. Turn the forward end, forming a square shouldered projection .200 inch long by .600 inch in diameter.

This forms the bolt nose, which is bored to a depth of .100 inch with an ID of .400 inch. In the center of lliis, form a fixed firing pin .060 inch to .065 inch in diameter and projecting .050 inch above the bolt face. This should have a rounded, hemispherical tip, which is formed by using a cutting tool ground for this purpose. This is used in the open-bolt gun. The closed bolt is made in the same manner and to the same dimensions, except that where the fixed firing pin was formed for the open bnlr, a hole is drilled instead, using an 065-inch drill. This hole should be started with a number one center drill, which is only used to establish the center, followed by the drill. The hole should be drilled deep enough (at least 1/2 inch) to meet a larger .156-inch hole, which is

Bottom View

.350"

.350"

Turn to a size which slides freely in Receiver

Relieve .C25"to .050" to reduce friction

350"

Turn to a size which slides freely in Receiver

Relieve .C25"to .050" to reduce friction

350"

Machine Pistol Bolt

Open-bolt version.

Bolt face is recessed .100' Firing pin is .065" dia. X .050" long

Homemade Hammer Machine Pistol
upside down for clarity.

drilled from the other end. Extreme care must be taken when using this small drill. It must be fed in very slowly, well lubricated, and cleane d frequently. If overloaded it will almost certainly break off in the hole, which will spoil the work because it will require more time and effort to remove it than to simply start over with another piece of material.

Reverse the bolt in the chuck and drill a hole to accept an M1911 Colt recoil spring. Since these springs measure approximately .435 inch in diameter, use a slightly larger drill to provide clearance. Either a 11.5-millimeter drill measuring .4528 inch or a 29/64 inch that measures .453 inch will suffice for this. The hole should be 2 1/2 inches deep.

The closed bolt must be drilled using three different diameters: one for the recoil spring, which is the same size and depth as for the other bolt; a smaller size to clear the firing pin head; and another for the firing pin body and return spring. These should be drilled to the depths and sizes shown in the drawing.

You can reduce friction by turning the bolt body to a diameter some .025 inch smaller than required, leaving three full diameter bands 3/8 to 1/2 inch wide, one at each end and one in the middle.

Cut a slot to allow installation of the extractor in the right side at the forward end. This will be in a nine o'clock position when viewed from the front. This should be 1/8 inch wide, 1 inch long, and .350-inch deep. Make a 3/16-inch-diameter spring pocket at the extreme rear end of the slot. This slot is easily cut with a 1/8-inch end mill and the spring pocket with a 3/16-inch end mill. It can also be done with the hand grinder or by hand by drilling intersecting holes to lemove the bulk of the material and finishing with files and chisels.

Turn the bolt upside down, with the extractor slot in the three o'clock position when viewed

M240 Cycle Operation

Closed-bolt, right side.

Tip Should Be Hemispherical. Protrusion .060"_

Tip Should Be Hemispherical. Protrusion .060"_

250" Dia.

FIRING PIN, Closed Bolt

Instoll Firing Pin Sten Gun

Recoil spring guide.

125"

.125"

COCKING LEVER

Spring pocket is .187" dia. ..300" deep

Note: Hole for magazine release pivot pin is drilled with Magazine in place and release pushed up against it.

I Magazine release.

from the front. A slot is first cut, 5/8 inch wide, 2 inches long, and 1/4 inch deep, measured from the front bolt face and on the bottom centerline. Then rotate the bolt 15 degrees and make an angled cut down one side of the opening. Rotate 30 degrees in the opposite direction, which will enable the same 15-degree angle to be cut along the other wall. Then, using a 3/16-inch end mill, cut a slot along each side of the bottom, leaving a strip .350 inch wide at the bottom of the bolt face. These are to provide clearance for the ejector as well as the magazine lips. The one on the left side, as viewed from the front and with the bolt upside down, provides clearance for the ejector and should be cut .225-inch deep. This is the one on the inside, on the opposite side from the ejection port. The other slot needs only to be .100 inch deep. The strip between the two grooves should be rounded on the edges and polished as smooth as possible, because this surface contacts and rubs against the top cartridge in the magazine as the bolt reciprocates.

If the closed bolt is used, you must cut a slot 3/8 inch wide and 11/4 inches long, beginning 1 1/2 inches back of the bolt face and extending along the centerline to the rear. The radiused corners of the slot, at least at the forward end, should be filed square. The back edge, at the bottom, should be relieved at a 45-degree angle. The hammer travels in this slot and contacts the firing pin at the front fare. Though not really necessary, if you cut this slot entirely through the top of the bolt, it will make access to the firing pin easier.

It is possible to cut these openings by hand, but it certainly isn't easy. By the time you are finished you'll wish that you had gone out and bought a milling machine or at least paid someone with one for an hour's work to do it for you. But if you must, it can be done.

Locate and scribe a centerline down the bottom side of the bolt. This can be done with the lathe, the same way we did the receiver. Locate and scribe two more lines, 3/8 inch from the centerline, and one on each side. Draw these lines, parallel to the centerline, from the front edge of the bolt to a point two inches to the rear. Draw another line connecting the two. Now, scribe another series of parallel lines 1/8 inch inside these lines.

A template can be made, either by tracing the drawing or by measuring directly off the magazine you intend to use. The template and dimensions shown in the drawings are correct for a Sten gun magazine. An outline of the opening to be made should be scribed on the bolt face.

The material inside these scribed lines must be removed by some means. If done with the milling machine, as already described, it isn't much of a job. If, however, you are required to do it by hand, you can figure on most of a day's work, several blisters, some sore muscles, and assorted cuts and bruises. You will probably decide that it can't be done several times before you finish. But don't give up; it can be done. The reason I am sure of this is because I had to do it on the first gun of this type I made.

Some type of depth stop is needed to prevent your drilling deeper than required. If a drill press is used, there will be no problem. Simply use the depth stop on the drill press. However, if a hand drill is the only kind available, some sort of stop must be attached directly to the drill bit. A collar can be made from a piece of tubing that is epox-ied or soldered in place, or from a nut or washer that will just slip over the drill. Make up both a 1/8- and 1/4-inch drill in this manner by securing a depth-limiting collar in place on each.

Center punch marks are made 1/4 inch apart around the inside scribe lines and drilled on the punch marks using the 1/8-inch drill first and then the 1/4-inch drill. The holes parallel to the centerline must be angled inward, toward the center, at an angle of 15 degrees. The included angle of the finished sides will be 30 degrees.

After these are drilled along both sides and the end, stand the bolt on end, face up, and drill another series of holes two inches deep. Enough material must be left to form the radiused portion as shown in the drawing. If you have to cut this opening in this fashion, I strongly recommend that you obtain a drill press with a good vise for the job.

With all the outline holes drilled to the proper depth and correctly spaced, there will be very little surplus metal remaining in the cavity that we want empty. To remove any remaining material, just slide a small chisel under one corner and hit it with a hammer. The entire slug of surplus material should fall free.

All that remains now is to remove enough additional metal to form an opening in the shape of the template. This will enable the bolt body to slide freely over and around the loaded magazine, allowing the radiused portion to pick up a cartridge and chamber it. Put a sturdy handle on a 10-inch file and wrap several layers of tape around the 4 or 5 inches adjacent to the handle. Then, by using both hands near the handle end, the forward end of the file can be used to greater advantage, together with chisels, to properly form and smooth the opening.

Make the extractor, as shown in the drawing, from 1/8-inch flat stock. Don't try to use common sheet metal for this. It will batter and deform at the hook end. Use high-grade material even if it means cutting a piece of car spring to the correct thickness or sawing a thin slice from the end of an axle to make it from. When cut to the shape and dimensions shown, put it in place in the extractor slot and drill the hinge pin hole. Place a close-fit-ting coil spring in the spring pocket and pin the extractor in place. It should open far enough at the front for the hook to snap over a case rim without binding. If the open-bolt version is used, you must use an unprimed case to test it.

,250"

Extractor

.100

When using the closed-bolt version, a firing pin must be made to the dimensions shown. A hole is drilled in the location shown for a cross pin to retain the firing pin. A close-fitting plug should be inserted in the firing pin hole to support the drill as it starts through the opening. If unsupported, the drill will deflect, or crawl, to the unsupported side and probably break. The firing pin must have a slot cut on one side to clear the retaining pin. It is assembled by putting the return spring in place over the firing pin body and inserting it in the bolt where it is held in place by the cross pin. The firing pin protrusion should be from .050 to .060 inch. This can be checked by holding a flat object flush against the end of the firing pin and opening. This will cause the tip to protrude from the bolt face, just as it would if pushed forward by the hammer. The firing pin should be made slightly longer than specified and cut to length after assembly and trial.

With the bolt inside the receiver and in its correct closed position, indicate the location for the cocking lever by marking through the slot in the receiver. The cocking lever must not contact the end of the slot. Remove the bolt from the receiver and drill the hole, first with a 1/4-inch drill, which can go all the way through the npen bolt but must stop at the hammer slot in the closed bolt. The hole is enlarged to 3/8-inch diameter for the first 1/4 inch. This will provide a shoulder to keep the cocking lever at its proper depth.

Make the cocking lever to the dimensions shown, at least for the end that fits into the bolt. The portion that protrudes outside the receiver can be of any shape or length desired. When assembled, the bolt must move back and forth freely, without binding.

Shape Bolt Drawing

.650"

.250"

Ejector

.650"

Shape Bolt Drawing

H i p JSu.J^^ JB mtre^ m

■ '

I

Above: Make magazine clearance cuts with milling machine.

Right: Angle sides of bolt cuts by using end mill.

Below: Make ejector and magazine lip clearance cuts by using end mill.

CAPTIONS FOR DRAWINGS ON FACING PAGE.

Extractor: Cut from 1/8-inch flat stock. Pivot pin hole is drilled through bolt body and extractor simultaneously. Hook end should be left slightly oversize-fitted to snap over cartridge rim during assembly.

Ejcctor: Cut from 12-gauge material. Semicircular cutout at rear to clear hammer spring. Horizontal leg is left oversize-fitted during assembly to almost contact bolt slot. Silver-soldered in place, flush with the inside left front edge of trigger housing bent as shown for alignment.

Bsp Smg Bolt Drawing

Top Left: Front view of bolt, showing relationship to magazine.

Top Right: Right side of finished bolt.

Upper Middle Right: Bottom view of finished bolt.

Middle Left: Bolt, front view.

Lower Middle Right: Bolt, top view with cocking handle.

Bottom Left: Closed bolt shown with recoil spring, guide, and cocking lever.

Bottc/m Right: Open bolt (lower) shown with closed bolt. The same recoil spring and guide are used on both versions.

9mm Bsp Machine Gun9mm Bsp Machine Gun

Was this article helpful?

0 0
Woodworking Tools and Installation Tips

Woodworking Tools and Installation Tips

There are a lot of things that either needs to be repaired, or put together when youre a homeowner. If youre a new homeowner, and have just gotten out of apartment style living, you might want to take this list with you to the hardware store. From remolding jobs to putting together furniture you can use these 5 power tools to get your stuff together. Dont forget too that youll need a few extra tools for other jobs around the house.

Get My Free Ebook


Responses

  • thomas martin
    How to layout a taper intersecting a taper at 30 degree angle?
    8 years ago

Post a comment