American "Bunny Gun" - Rook Rifle Concept
May 12, 2020 11:20:45 GMT -5
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Post by coltnewservice45 on May 12, 2020 11:20:45 GMT -5
The attraction for me of the British "Rook Rifle" concept is that low-powered handgun rounds, when fired from a rifle are relatively quiet, like firing standard velocity .22 LR, but they hit MUCH harder than a rimfire, being useful on larger game or varmints.
The .360 No. 5 and .380 Rook Rifle cartridges were used for culling "park deer" in Britain before WW1. These particular black powder Rook Rifle cartridges were similar in dimensions, velocity and energy to the .38 Short Colt or .38 S&W cartridges and were popular in pocket and Constabulary revolvers of their pre-WW1 era.
The .38 S&W cartridge dates from that same era. When fired out of a rifle you have a modest gain in velocity, but the potential for adiabatic expansion is limited by its tiny powder charge and the greater expansion ratio of the longer barrel. The result is that standard-pressure revolver loads, operating at black powder pressures, with fast-burning powders like Bullseye, deliver ballistics from a rifle-length barrel very much like a .38 Special wadcutter fired from a 6-inch revolver. The .38 Special wadcutter performs on small game out of proportion to its kinetic energy, depositing about the same energy into a gelatin block before exiting that .45 ACP hardball does. My .38 S&W hand loads utilize cast bullets which are heavy for the caliber, 190-240 grains, having a large meplat, because any expansion is absolutely NOT in the cards at the 700-800 fps velocities we are talking about.
I have no interest in trying to see how powerful a load I can assemble for my .38 S&W Lettuce Protector. I have barrels of other calibers which do that. The design intent is a small capacity cartridge having ballistics approximating a large-caliber air rifle. Heavy, blunt, slow bullet, low velocity, low noise.
The .38 S&W case is ideal in this application. Because my goal was to use as heavy a bullet as possible, launched as slow as would reliably exit the barrel, I used a 1:10" twist 9mm Parabellum barrel to adequately stabilize bullets as heavy as 240 grains, at the lowest velocity which would reliably exit the barrel. The goal was a stealthy, hard hitter, capable of shooting clear through both shoulders of deer at garden ranges, or lengthwise for a Texas Heart Shot, if that was all that presented, but would not require a tax stamp for a "can." John Taylor fitted a Green Mountain "Gunsmith Special" 9mm Parabellum barrel blank and chambered it with a Manson .38 S&W "Rook Rifle" reamer having a 3 degrees Basic forcing cone, with a major diameter of .363" at the case mouth, which engraves the nose of the bullet upon chambering, like forcing Eley Tenex in your old Winchester 52 match rifle.
The resulting "Lettuce Protector" is 34-1/2 inches long and weighs 4-1/2 pounds and is capable of inch 5-shot groups with simple open sights at 25 yards.
The Accurate 36-240H bullet attains about 720 fps from the 20-inch barrel with 3 grains of AutoComp.
In field use of handgun-caliber rifles shooting subsonic loads, I have found it best to utilize the "optimum trajectory" in which maximum bullet rise does not exceed about 4 inches. With iron sights you take a 6:00 hold on a typical small game animal until the front sight bead about covers the critter, and then blot him out and shoot. With the .38 S&W cartridge this works out to a 75 yard zero and a 90-yard "point blank" at which the path of the trajectory drops 4" below line of sight. The 240-grain bullet arriving downrange with almost no noise to help the target identify where the shot came from would be an unpleasant surprise to any intruder, either 2-legged or four-legged. Penetration of the heavy, well-stabilized bullet is astounding, penetrating straight through a stack of gallon water jugs with zero yaw, like a laser, finally stopping in the EIGHTH gallon jug!
Just the thing for those BIG Texas-sized Wabbits!
The .360 No. 5 and .380 Rook Rifle cartridges were used for culling "park deer" in Britain before WW1. These particular black powder Rook Rifle cartridges were similar in dimensions, velocity and energy to the .38 Short Colt or .38 S&W cartridges and were popular in pocket and Constabulary revolvers of their pre-WW1 era.
The .38 S&W cartridge dates from that same era. When fired out of a rifle you have a modest gain in velocity, but the potential for adiabatic expansion is limited by its tiny powder charge and the greater expansion ratio of the longer barrel. The result is that standard-pressure revolver loads, operating at black powder pressures, with fast-burning powders like Bullseye, deliver ballistics from a rifle-length barrel very much like a .38 Special wadcutter fired from a 6-inch revolver. The .38 Special wadcutter performs on small game out of proportion to its kinetic energy, depositing about the same energy into a gelatin block before exiting that .45 ACP hardball does. My .38 S&W hand loads utilize cast bullets which are heavy for the caliber, 190-240 grains, having a large meplat, because any expansion is absolutely NOT in the cards at the 700-800 fps velocities we are talking about.
I have no interest in trying to see how powerful a load I can assemble for my .38 S&W Lettuce Protector. I have barrels of other calibers which do that. The design intent is a small capacity cartridge having ballistics approximating a large-caliber air rifle. Heavy, blunt, slow bullet, low velocity, low noise.
The .38 S&W case is ideal in this application. Because my goal was to use as heavy a bullet as possible, launched as slow as would reliably exit the barrel, I used a 1:10" twist 9mm Parabellum barrel to adequately stabilize bullets as heavy as 240 grains, at the lowest velocity which would reliably exit the barrel. The goal was a stealthy, hard hitter, capable of shooting clear through both shoulders of deer at garden ranges, or lengthwise for a Texas Heart Shot, if that was all that presented, but would not require a tax stamp for a "can." John Taylor fitted a Green Mountain "Gunsmith Special" 9mm Parabellum barrel blank and chambered it with a Manson .38 S&W "Rook Rifle" reamer having a 3 degrees Basic forcing cone, with a major diameter of .363" at the case mouth, which engraves the nose of the bullet upon chambering, like forcing Eley Tenex in your old Winchester 52 match rifle.
The resulting "Lettuce Protector" is 34-1/2 inches long and weighs 4-1/2 pounds and is capable of inch 5-shot groups with simple open sights at 25 yards.
The Accurate 36-240H bullet attains about 720 fps from the 20-inch barrel with 3 grains of AutoComp.
In field use of handgun-caliber rifles shooting subsonic loads, I have found it best to utilize the "optimum trajectory" in which maximum bullet rise does not exceed about 4 inches. With iron sights you take a 6:00 hold on a typical small game animal until the front sight bead about covers the critter, and then blot him out and shoot. With the .38 S&W cartridge this works out to a 75 yard zero and a 90-yard "point blank" at which the path of the trajectory drops 4" below line of sight. The 240-grain bullet arriving downrange with almost no noise to help the target identify where the shot came from would be an unpleasant surprise to any intruder, either 2-legged or four-legged. Penetration of the heavy, well-stabilized bullet is astounding, penetrating straight through a stack of gallon water jugs with zero yaw, like a laser, finally stopping in the EIGHTH gallon jug!Just the thing for those BIG Texas-sized Wabbits!
