Baixe 50cal Rifle Construction Manual e outras Manuais, Projetos, Pesquisas em PDF para Engenharia Militar, somente na Docsity! THE .50-CALIBER RIFLE CONSTRUCTION MANUAL WARNING Although at the time this book was published it was perfectly legal for an individual to manufacture a firearm for personal use, exper- imental purposes, or research and development, it is possible that new laws have been enacted since then. It is the reader's responsibility to carefully research all pertinent laws before any firearm construction is attempted. Technical data presented here on the construction, use, adjustment, and alteration of firearms inevitably reflect the author's beliefs and experiences with particular firearms, equipment, and components under specific circumstances that the reader cannot duplicate exactly. The information in this book should therefore be used for guidance only and approached with great caution. Neither the author, publish- er, nor any distributor assumes any responsibility for the use or misuse of information contained in this book. This book is presented for aca- demic study onhy. TABLE OF CONTENTS Introduction 1 Receiver 3 Barrel 7 Barrel Accessories 13 Bolt 17 Trigger Assembly 29 Butt Stock 41 Scope Mount 43 Bipod 43 Muzzle Brake 47 Assembly and Firing 61 vii INTRODUCTION Some time ago when Paladin and 1 made The Home Workshop -50-Caliber Sniper Rifle video, we opened a can of worms that nei- ther of us had anticipated. This video was never intended as a construction guide whereby one could simply look at it and build a gun; rather it was simply to show methods used to fabricate the component parts. It never occurred to me that anyone would actu- ally expect to build such a gun simply from a video. However, shortly after the video was released both Paladin and I were deluged with requests, even demands, for a set of drawings and dimensions to allow the building of such a gun. I began the project, but since 1 am now 72 years old, almost blind, and afflict- ed with Parkinson's disease, my work went rather slowly. But here itis, finally, and I apologize for any distress or problems the delay may have caused anyone. Many people seem to feel that the .50 is an awesome small cannon that is dangerous to shoot and only good for criminal operation. In truth, this gun, just like any other, is no more dangerous than the person shooting it, and if any serious crimes have been committed with one, the news has been kept awfully quiet. I have never heard of an incidence. Actually, the only thing more dangerous about a .50-caliber than any other rifle is its greater range. As long as a suitable backstop is used and the shooter knows where the bullet is going, even this complaint is nullified. As of this writing it is legal to build such a gun for one's own use, provided the maker's name and address and a serial number are stamped on the receiver. Keep your eyes and ears open on this though. There has already been at least one bill introduced in the U.S. Congress trying to make .50-caliber rifles illegal. This bill did- n't get anywhere, but rest assured there will be more attempts. Sooner or later the politicians will sneak a bill through to outlaw the .50-caliber rifle—and they probably won't even tell us about it until they come to seize the weapons. So stay alert. Please remember that since we have no control over the mate- rials or workmanship used in the project, neither Paladin nor I can accept any responsibility whatever regarding the safety or condi- tion of a gun that someone else makes. However, if proper materi- als are used and heat-treated correctly, a decent chamber is cut, and the firing pin is set at the right protrusion, there is no reason why your gun should not be safe to shoot. Mine is. Jt is recommended that you obtain a copy of The Home Workshop .50-Caliber Sniper Rifle video before you attempt to build THE .50-CALIBER RIFLE CONSTRUCTION MANUAL Barrel and receiver. Front end of receiver. RECEIVER Receiver, showing ejection port É Trigger mounting bracket and middle threaded section for barrel-retaining nut. THE .50-CALIBER RIFLE CONSTRUCTION MANUAL Breech end of barrel with locking lug section in place. arma lag aBrs” 4.250" —-w—l sw nim 250” Dia, 4875” 1.250" + 6 ROWS OF TWO EACH RIGHT SIDE WELD A ese SCALE 1/1 RECEIVER BOTTOM RIGHT SIDE RECEIVER BOTTOM BARREL The barrel can be turned from a commercial blank or made from a surplus military barrel. M2 barrels are presently available from Oyster Bay Industries (31 South Street, Oyster Bay, NY 11771). These are new barrels, and their biggest drawback is that they have enough Cosmoline on each one to protect a tank. On the other hand, they contain enough surplus material to allow making up most of the other barrel paris. Incduded in the barrel assembly are the barrel proper, barrel extension, barrel support sleeve, muzzle brake, and barrel-retain- ing nut. The M2 barrel is sawed into sections large enough to make the designated parts. The barrel sections, as well as all other parts, are squared on the ends and turned to size. All threads are 12 threads per inch (TPI). Both the barrel section, which contacts the barrel retainer, and the retainer are turned with a matching 4-dégree taper. This causes a solid, in-line lock-up and support for the barrel at the breech end. The barrel extension must have three locking lugs (which mate with the bolt lugs) machined into it. This is best done with some sort of dividing head. But if none is available, don't give up. Wrap a length of masking tape around the diam- eter of the part, measuring the length precisely. This is then divided into three parts and rewrapped, and their positions are marked on the barrel extension. These marks are then used as centerlines to cut the lugs with the milling machine. Some file work may be required in the shaping of these. If care is taken, a precise fit will result. When smaller lathes are used for this, it will be necessary to tum the barrel one-half length at a time (assuming that a large enough hole to accept the smaller portion exists). If the end with the smaller diameter is pushed through the headstock, the larger end can be turned to size and threaded. Do not attempt to cham- ber the barrel until the barrel extension and bolt ate made. The bar- rel is then reversed in the spindle and the smaller portion tumed. The threads for the muzzle brake and barrel-retaining nut are cut at this time. The military surplus barrels from Oyster Bay are heat-treated to a hardness that is slower and harder to machine than that of com- mercial barrels. However, the barrels are tougher and will usually wear beiter arfá last longer than their commercial counterparts. THE .50-CALIBER RIFLE CONSTRUCTION MANUAL | Ti ] 1.220" 1.300" LENGTH AS DESIRED . 7 FROM BARREL NUT TO MUZZLE —— meme Death 10 ' ' ! BARREL, FORWARD END BARREL ACCESSORIES The barrel-retaining sleeve is made from 4:40 or 4340 material. This should be a ship fit inside the receiver tube. The inside of this part isleeve) should be closely fitted by tapering to the same dimensions as the barrel shank (I used 4 degrees) so that when pulled into place inside the receiver, and with the barrel nut tight and under a slight amount of tension, a solid installation results. In many cases this enhances accuracy. The muzzle can now be crowned and the threads cut for the muzzie brake installation and the barrel nut. Both are cut 12 TPI. The barrel extension, which contains the locking lugs that mate with the bolt lugs, is made from a close-fitting section of good- quality steel, preferably 4140 or 4340. A lúinch hole is bored through the center of the part The hole is then enlarged to 1 1/2 inches (1.500 inches) inside diameter by 1 3/4 inches (1.750 inches) in depth. The shoulder remaining at the bottom of this enlarge- ment should be smooth and square since the bolt lugs lock against this. The front end is now threaded to fit on the barrel tenon. This is 12 TPI pitch by 1 1/2 inches diameter by 1 1/4 inches (1.250 inch- es) deep. This thread joint should fit snugly, with some effort required to screw it home. The barrel should ence again be placed in the lathe and the chamber cut. 1 recommend that a roughing reamer be used first, followed by the finish reamer. Accurate headspace gauges should also be obtained and used because there is sometimes quite a bit of difference between cartridges obtained from differ- ent sources. Clymer Manufacturing Company is an excellent source for these gauges. It should be emphasized here that ammunition obtained from different sources would not even fit into a standard chamber. US. military and Istaeli ammnunitions are fairly consistent, but those from some other countries may not even allow the bolt to close. Ammunition must be made to fit a standard chamber, not vice versa. THE .50-CALIBER RIFLE CONSTRUCTION MANUAL 120º pl dr he THREAD 12 TPI RR | 10” 1.500" I BARREL EXTENSION 16 E ee ” aa BOLT The bolt, constructed from the same material as the barrel extension (4130, 4350), is only slightly more difficult than those built for smaller actions. It's just larger and takes longer. However, several drill extensions must be made up to drill the firing-pin hole through the bolt. With the ends of the blank squared, a small hole is started through one end using a &2 center drill. This is then enlarged and lengthened with a 3/32-inch (.087-inch) drill. This will provide the opening in the bolt face for the smaller end of the firing pin. Drill this to a depth of 3/4 inch or so. The drill used here, as well as all the others used in this bolt construction, should be new and sharp. Whenin use, they should be withdrawn frequently and cleaned and relubricated. A counterbore, two hundred thousandths of an inch deep and to a diameter that will just accept a case head, is machined in the bolt face, The bolt face so formed must be very smooth. While chucked in this position, the bolt body should be turned to a diameter of 1 1/2 inches (1.50 inches), as shown in the draw- ing, and the groove should be cut to form the flange that forms the locking lugs. The rear side of “his groove should be very smooth and square with the bolt body. The rest of the bolt body could be kept at a constant 2-inch diameter. But tuming it as shown and adding the outer sleeve establish clearance for the sear and loading ramp, as well as reducing friction considerably. At this point, the bolt is reversed in the chuck (preferably a four-jaw one) and centered using a dial indicator. You cannow pro- ceed to drill and bore the inside to the dimensions shown. You will need to add extensions to some of the drills. Drill the holes as deep as possible, using new, sharp drills before using the extended ones. With luck and all possible care, this hole will meet and center on the small hole started from the other end. A slot must be milled, as shown, to provide clearance for the sear, and the locking lugs must be machined to mate with the lugs in the barrel extension. With the barrel in place and the bolt in a forward position, ready to close but unlocked, the bolt handle position is scribed “hrough the opening in the receiver slot. The bolt is removed from ihe receiver, and the handle is welded in place. This should be made up slightly oversized and fitted by removing material to the point that the bolt works freely. That is, it opens and closes and moves forward and back without effort. The extractor should be machined and installed in the upper sight-hand bolt lug. When the bolt is opened, this pulls the empty THE .50-CALIBER RIFLE CONSTRUCTION MANUAL case to a point where a finger can be hooked over the mouth of the empty case and the case pulled free. No ejector is used in this design since, as a single shot, it is desirable to save the empty case for further use with as little detormation as possible. The cocking cam is located and marked through the receiver slot and cut as shown. As in other instances, this should be fitted during construction and assembly and may not conform exactly to the dimensions shown. The firing pin is turned from 1/2-inch (.50-inch) material. This is best done in three stages: (1) forming the front portion, (2) reversing the pin and tuming the rear section to size, and (3) threading the rear section, with the front portion formed first. The bushing, which holds the firing pin in place is made as shown. The cocking piece also is made from 2 1/4-inch-diameter material (2.250-inch-diameter) and, again, fitted as assembled. A hole is drilled through both the bolt body and the firing pin bushing to hold the assembly in place. This should be done in one operation, with the parts assembled and in place. The entire assem- bly is now fitted and polished until smooth operation is achieved. The three bolt-lug openings are laid out on the face of the bolt, an equal distance apart, using a dividing head or spacer of some sort. If neither of the latter is available, this spacing can be accom- plished by wrapping a piece of masking tape around the diameter and marking the exact diameter on the tape, which is then removed and marked off in three parts. It is then again wrapped around the bolt, whereby each line becomes the centerline of each lug. The openings can now be cut, 1/2-inch wide and 1/4-inch deep, using a 1/4-inch end mill. The radiused corners can be made square, if desired, with the use of a small square file. No attempt should be made to chamber the barrel until both the bolt and barrel extension are finished. The barrel-retaining nut is a straightforward lathe job. It is threaded inside to match the barrel threads. The outside is turned to the same diameter as the receiver tube, and one end is turned to just fit inside the tube. Bolt with firing mechanism removed. Firing mechanism. THE .50-CALIBER RIFLE CONSTRUCTION MANUAL Es Lam] | 8.250" 1.0" k [ 800" prT E e as = [1 | so” 750" pela 750" | BOLT 22 BOL recreio + ro efesepa o om adere gde sr obum he D+ A + JT|IT THE .50-CALIBER RIFLE CONSTRUCTION MANUAL BOLT, END VIEW 26 BOLT SLEEVE TRIGGER ASSEMBLY A mounting bracket for the trigger and sear to hinge from is made by milling a slot through a piece of 5/ B-inch (.625-inch) square material that is contoured on the upper side to fit closely against the receiver body. It is then silver-soldered or welded in place. Both the trigger and sear should be cut to the approximate shapes and dimensions shown. Some fitting may be required before these parts work as desired. Itis a good idea to drill the pivot pin holes through the mounting bracket first and then put the trigger and sear in place and mark the hole locations through the previously drilled holes. This can save some fitting, The trigger housing is made by forming 14-gauge sheet metal around a block and welding the ends and trigger guard in place. 2a The trigger guard could be bent to shape from a sheet-metal strip and welded in place, but the milled-steel guard, made similar to the one shown, looks quite a lot beiter. There are those who would have you believe that a safety is not necessary on a single-shot firearm. If you ate of this mind-set, then by all means leave it off. I£, like me, you want to be pretty sure that the sear won't slip off and cause the rifle to fire as the bolt closes or otherwise fire when you don't want it to, then you should take a little extra time and add a safety. The grip is made from a hardwood block and can be left in its natural color with a clear finish or painted black, whichever suits you best. THE .50-CALIBER RIFLE CONSTRUCTION MANUAL Trigger housing, bottom view. Grip. Er] TRIGGER ASSEMBLY Grip and trigger housing assembled. 33 E .SO-CALIBER RIFI LE CONSTRUCTION MANUAL TRIGGER ASSEMBLY + | 700” 1.375” TRIGGER HOUSING PATTERN peido 6.350" 37 2.450" THE .50-CALIBER RIFLE CONSTRUCTION MANUAL WELD TRIGGER HOUSING ASSEMBLY SHAPE TO TASTE 38 TRIGGER ASSEMBLY a de 2 A, Em fre ss po al co pe S.750" GRIP, SHAPE OPTIONAL 39 THE .50-CALIBER RIFLE CONSTRUCTION MANUAL WELD A NL” — ( BUTT PLATE 42 SCOPE MOUNT A base to mount the scope on (which will raise the sight line approximately 1 inch higher than is usual on a standard rifle) must be constructed. Even though this .50-caliber rifle generates no more recoil than most other large-caliber rifles, this base should be solid and sturdy. Two short steel sections should be contoured to fit against the receiver tube and silver-soldered in place atop the receiver in the location that the bases will occupy. These simply add thread area as they are drilled and tapped through both these and the receiver. Two steel blocks are contoured to fit the receiver tube, and a slot is cut down the center of each to fit over each of the reinfore- ing bars described above. Depending on the scope bases you intend to use, a connecting 43 bar is made to accept it and silver-soldered to the top of the ele- vating blocks. The one shown in the drawing is for use with Weaver-type rings; if the steel rings used are of the same type as those made by Redfield and others, a sturdy mounting system is ensured. If other types of rings are used, they can simply be screwed to the blocks as they would be on a standard rifle. This base should be drilled to accept four screws and clamped in place and the mounting screw holes drilled through the receiv- er. They are then tapped to accept proper screws. 1 recommend using 10 x 32 screws for this. Be sure that you have enough eye relief to avoid being hitin the eye with the scope when firing. Try to mount the scope as far for- ward as possible while retaining a complete field of view. THE .50-CALIBER RIFLE CONSTRUCTION MANUAL Scope and mount in place on rifle. A rifle such as this produces quite a lot of torque, or twisting, to the right when fired, so a sturdy bipod is in order. It would be nice if one could simply obtain one vf the ready-made ones and mount it in place. The trouble is, there are simply no satisfactory ones available-—at least not that I know of. The center section, which mounts at the front end of the receiv- er and is held in place with screws, is machined from 2-inch round stock, This should be contoured to a close fit with the receiver and a bar silver-soldered over the mounting position and drilled and tapped just like the scope-mount screw holes were. The hinged ends of the legs are made from the same 2-inch round stock, with the legs made from .065-inch-wall-thickness 47 seamiess tubing welded in place. The lower ends can be shaped as shown or modified as desired and pinned or welded in place. A template should be made to locate the locking pin holes. To be effective these holes must line up exactly. If they don't, there is a good chance that the bipod will collapse when the rifle is fired. The spring-loaded detent, or locking, pins are made from dríll rod with the push buttons silver-soldered in place. In use, the button is pushed in and the leg extended or fold- ed against the receiver, where it will lock in place when the hole and pin line up and the spring forces the detent pin into place. This process is repeated on the other side to place both legs in the same position. THE .50-CALIBER RIFLE CONSTRUCTION MANUAL Bipod ready for mounting. z B 2 ê £ E E z Q ê a Lower end of bipod leg. THE .SO-CALIBER RIFLE CONSTRUCTION MANUAL Finished bipod. 250" BIPOD 1.125" R THREAD 1/4 x 28 -250" DIAMETER 4.500" atm meme T =. 700" + BIPOD, CENTER SECTION 53 THE .SO-CALIBER RIFLE CONSTRUCTION MANUAL . THREAD TO MATE WITH | 10, OUTER LEG —- 500" 10º . ——— , sitio — % r O + 5º TAPER o 7.500” L 750" 625" BIPOD, INNER LEG 54 THE .50-CALIBER RIFLE CONSTRUCTION MANUAL The exit hole must be bored slightly larger than the bullet diam- eter (.510 to .520) inch. To ensure concentricity, this is done while the barrel is still in the lathe, If any misalignment is present, the bullet may rub one side of the exit hole, resulting in poor accuracy. Tt is also possible to fabricate a fairly efficient brake by welding a plug in each end of a length of seamless tubing and boring the small exit in one end and threading the other. It may not look quite as good, but it is easier and faster to build than the one described. Please note that the length and diameters shown are not absolute. You can probably build one shorter or longer or smaller in diameter with no ill effects, The sizes shown work for me, and | have never had occasion to change them. Side view of muzzle brake. MUZZLE BRAKE End view of muzzle brake, 59 2.00"