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The firing pin must crush the rim of the .22 caliber rimfire cartridge to detonate it. Thus, the hole for the firing pin in the breech plug must be drilled off center, as shown.
A .38 S&W, .38 Special, and .357 Magnum all have bullet diameters that will fit in 1/4" Schedule 40 pipe. However, in each case the pipe must be drilled out to accept the diameter of the shell casing. See Figure 4-2. A 25/64" fractional drill or a letter size W drill are the bit sizes to use. Drill to a depth of 1 1/4".
A .41 Magnum bullet will fit in 3/8" Schedule 80 pipe. The pipe must be drilled out to accept the shell casing. See Figure 4-2. Use a 7/16" bit and drill to a depth of 1 1/4".
Wifh some calibers, the bullet diameter will fit in the pipe but the shell diameter will not. The necessary clearance can be obtained by drilling oui the pipe ID to the appropriate diameter and depth. The arrow in the illustration points to the potential conflict in clearance.
The .375 Winchester will fit in 3/8" Schedule 80 pipe. No drilling is necessary.
The .44 special, .44 Magnum, .45 Auto Rim, .45 Colt, and .410 bore shotgun will all fit in 3/8" Schedule 40 pipe. No drilling is required. The .444 Marlin is a sloppy fit in this size pipe and I would recommend against its use.
The .45-70 Govt, bullet will fit in 3/8" Schedule 40 pipe and in 1/2" Schedule 160 pipe. Both pipe sizes require drilling with a 33/64" bit to a depth of 2 1/8" for shell casing clearance.
The .35 Remington is a necked cartridge which will fit in 3/8" Schedule 80 pipe with a bit of drilling. Drill with a 15/32" bit to a depth of just over 1 9/16". The depth is fairly critical but is best determined by trial and error. It is critical because the shell is rimless and will be held in place by the shoulder instead of by a rim.
Straight-sided, Rimless Shells
Several shells have straight sides and would lend themselves to the type of firearm described in Chapter 3 except that they lack rims. "Rims" can be added, however, by the use of retaining rings. See Figure 4-3. It may be necessary to file off part of the retaining ring's "ear" to obtain clearance within the gun's collar.
The .30 Ml Carbine and the .32 Auto are both straight-sided shells that will fit into 1/4" Schedule 40 pipe. They are both rimless, but a 3/8" retaining ring can be used to solve that problem.
The 6ulfel of the .380 ACP and of the 9mm Parabellum will fit in 1/4" Schedule 40 pipe. In both instances the pipe must be drilled out with a 13/32" bit to a depth of one inch to accept the shell casing. Use 3/8" retaining rings to create rims.
The .45 ACP and the .45 Winchester Magnum will fit in 3/8" Schedule 40 pipe. No drilling is required. Use 1/2" retaining rings for rims.
Retaining rings and the special pliers with which to install and remove them can be obtained at an automotive supply store. The sizes indicated here can actually be put on with the fingers and do not require special pliers (assuming you have fairly strong fingers, of course).
By employing pipe reducers, it is possible to use necked cartridges in the type of firearm described in Chapter 3. The neck rather than the rim holds the cartridge in place. Therefore, retaining rings are not necessary even on rimless shells. Because gaps are inevitable between the cartridge and the chamber holding it, many hroken shell cases and extraction problems should be expected.
Using adapters for necked cartridges. "A" is the breech plug. "B" is the collar. "C" is the cartridge itself. "D" is the nipple which must be custom cul to length for each caliber and shell sue. "E" is the reducer — the heart of the whole affair. "F" is the space, a kind of headspace, where a potential 6lou;ou( of the shell casing can occur. "G" is the barrel.
When using the following directions, refer to Figure 4-4 to see the role being played by the component in question. These directions deal with diameters, not lengths. It is suggested that the nipple be 3" long to start, sawn to approximate length, and filed to finish length — being assembled and disassembled as needed for tried measurements each step of the way. In each case, the collar and plug required is the same nominal size as the large end of the reducer.
For .22 Hornet and .22K Hornet (pistol shell/, use 1/8" Schedule 40 pipe for barrel; 1/4" Schedule 80 nipple; and a 1/4" to 1/8" reducer.
For .222, .222 Remington Magnum, .223, .221 Remington Fireball (pistol shell/, use 1/8" Schedule 40 pipe for barrel; 1/4" Schedule 40 nipple drilled out with a 25/64" fractional or letter size W bit; and a 1/4" to 1/8" reducer.
For .22 PPC, 6mm PPC, .220 Swift, use 1/8" Schedule 40 pipe for barrel; 3/8" Schedule 80 nipple drilled out to 29/64"; and a 3/8" to 1/8" reducer.
For .225 Winchester: use 1/8" Schedule 40 pipe for barrel; 3/8" Schedule 80 nipple; and a 3/8" to 1/8" reducer.
For .22-250: use 1/8" Schedule 40 pipe for barrel; 3/8" Schedule 80 nipple drilled out to 15/32"; and a 3/8" to 1/8" reducer.
For .250 Savage: use 1/4" Schedule 80 pipe for barrel; 3/8" Schedule 80 nipple drilled out to 15/32"; and a 3/8" to 1/4" reducer.
For .257 Roberts, .25-06 Remington, and 6.5 x 55mm: use 1/4" Schedule 80 pipe for barrel; 3/8" Schedule 80 nipple drilled out to 31/64"; and 3/8" to 1/4" reducer.
For .270 Winchester, 7 x 57mm Mauser, 7mm Express Remington (.280 Rem.): use 1/4" Schedule 40 pipe for barrel; 3/8" Schedule 40 nipple; and a 3/8" to 1/4" reducer. (Note: the .270 Winchester is a sloppy fit and I recommend against using it unless a small powder charge is employed. The bullet can be pulled from a factory-loaded shell, for example, half the powder removed, and the bullet re-installed in the shell.)
For .284 Winchester: use 1/4" Schedule 40 pipe for barrel; 3/8" Schedule 40 nipple drilled out to 33/64"; and a 3/8" to 1/4" reducer.
For .30-30, .32 Winchester Special, and .30 Herrett (pistol shell): use 1/4" Schedule 40 pipe for barrel; 3/8" Schedule 80 nipple; and a 3/8" to 1/4" reducer.
For .300 Savage, .308 Winchester (7.62mm NATO), .30-40 Krag, .30-06, 8 x 57mm Mauser, and 8mm/06: use 1/4" Schedule 40 pipe for barrel; 3/8" Schedule 40 nipple; and a 3/8" to 1/4" reducer.
For .303 British: Use 1/4" Schedule 40 pipe for barrel; 3/8" Schedule 80 nipple drilled out to 13/32"; and a 3/8" to 1/4" reducer.
A quick follow-up shot is often nearly as valuable to a hunter as the firearm itself. The single shot shown in Chapter 3 can be converted to a double barrel with some rework.
The second barrel is mounted on top of the first barrel. The two barrels are fastened together by a short portion of bolt, threaded on both ends, connecting the two collars. To give the bolt, which 1 am terming a "lug," as much seating depth as possible, it is necessary to grind a flat spot on the threads of each barrel, thereby creating clearance for each end of the lug. Doing so makes for much trial assembly, disassembly, and reassembly. The steps follow:
1. On a single shot already constructed, mark the collar with a prick punch where the connecting lug is to fasten. The second barrel is to be on top, remember.
2. Remove the collar from the single shot. Drill and tap for the connecting lug.
3. Re-assemble the collar and barrel so that the shell is seated properly.
4. Mark the barrel threads with a prick punch where a flat spot is to be ground on the barrel threads. See Figure 4-5.
5. Again disassemble the collar and barrel and grind a flat spot on the barrel threads. Another way to create clearance for the end of the connecting lug is to use a large diameter bit and drill a shallow countersink hole. See Figure 4-6.
6. Re-assemble the barrel and collar so that the shell is seated properly and so that the tapped lug hole lines up with the flat spot.
7. Make a second barrel-collar-breech plug assembly in which a shell can be properly seated.
8. Mark, drill, and tap a lug hole; then disassemble and grind clearance for the end of the lug, similar to what was done on the first barrel.
9. Re-assemble the second barrel and collar, making sure the shell seats properly and that the lug hole lines up with the flat spot.
10. Measure and cut a lug. Collar thicknesses vary, so no single dimension can be given. Cut a little over-long then disassemble and re-assemble as necessary, trimming the lug length as appropriate.
11. Assemble the second barrel to the gun as shown in Figure 4-7.
12. Cut and drill a piece of hardwood as shown in Figure 4-8. The distance between the two barrel holes equals the thickness of the two collars at the rear end of the barrels. When drilling the barrel holes, back up the hardwood being drilled with a piece of scrap to prevent splitting. The small holes at the bottom are for wood screws which fasten into the end of the foregrip.
13. Insert both barrels chrough the hardwood and fasten into the end of the foregrip with one screw. That screw acts as a pivot and you can wiggle the barrels back and forth until they are properly aligned (parallel). Then, put in the second screw. See Figure 4-9.
A shallow hole (not penetrating the sidewall) can be drilled for clearance instead of grinding or filing a flat spot.
14. The next step is to make a hammer for the second barrel. Install a longer pivot pin, install both hammers on the same pin, and space them with washers as needed. Attach a spring to drive the second hammer on the opposite side of the gun from the spring which drives the first hammer. See Figure 4-10.
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