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Showing content with the highest reputation on 06/15/2020 in all areas

  1. 1 point
    T-90Ms and BMPTs being moved to Moscow Other vehicles
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    L to R: .224 Zoomer Magnum, .22 Rapier, .237 Antidote, .257 Flap, .283 Fudd.
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    CONFIDENTIAL AN EVALUATION OF CANDIDATE RIFLE CALIBERS FOR THE SIOUX SCOUTS STANDARD SEMIAUTOMATIC RIFLE (SSR) THUNDER BASIN PROVING GROUNDS September 25th, 2222 -cartridges for five candidate calibers and several chambered barrels each were received for testing during the week of July 7th, 2222. These were from teams lead by Curler, Neelam, Flapper, and Tockson, and two projectiles with a shared case from a team led by Griffin. The measured characteristics of their respective rounds were as follows: .224 cal (Curler): Case Length: 1.875 Base Diameter: 0.408 Case Taper: 0.5 deg Shoulder angle: 25 deg Neck length: 0.233 Rim thickness: 0.049 Rim height: 0.123 Groove angle: 36 Bullet diameter: 0.224 Bullet length: 1.1298 Cartridge overall length: 2.576 Proposed case capacity: 38.56 grs H2O Measured case capacity: 38.67 grs H2O Proposed bullet weight: 76.07 Measured bullet weight: 76.07 Proposed i7FF: 0.853 Measured i7FF: 0.796 Proposed G7 BC: 0.254 Measured G7 BC: 0.278 .224 cal (Neelam): Case Length: 2.00 Base Diameter: 0.400 Case Taper: 0.80 deg Shoulder angle: 25 deg Neck length: 0.220 Rim thickness: 0.060 Rim height: 0.139 Groove angle: 45 Bullet diameter: 0.224 Bullet length: 1.260 Cartridge overall length: 2.71 Proposed case capacity: N/A Measured case capacity: 37.61 Proposed bullet weight: 83.3 Measured bullet weight: 84.0 Proposed i7FF: 0.801 Measured i7FF: 0.682 Proposed G7 BC: 0.296 Measured G7 BC: 0.351 .243 cal (Griffin): Case Length: 1.85 Base Diameter: 0.4 Case Taper: 0.5 deg Shoulder angle: 25 deg Neck length: 0.237 Rim thickness: 0.060 Rim height: 0.1274 Groove angle: 45 deg Bullet diameter: 0.243 Bullet length: 1.422 Cartridge overall length: 2.8 Proposed case capacity: 35.75 grs H2O Measured case capacity: 35.86 grs H2O Proposed bullet weight: 85.75 Measured bullet weight: 84.65 Proposed bullet weight: 103.2 Measured bullet weight: 106.0 Proposed i7FF: 0.78 Measured i7FF: 0.618 Proposed G7 BC: 0.266 Measured G7 BC: 0.331 .257 cal (Flapper): Case Length: 1.975 Base Diameter: 0.473 Case Taper: 0.50 deg Shoulder angle: 25 deg Neck length: 0.244 Rim thickness: 0.0539 Rim height: 0.152 Groove angle: 36.44 deg Bullet diameter: 0.257 Bullet length: 1.374 Cartridge overall length: 2.8 Proposed case capacity: 52.22 grs H2O Measured case capacity: 52.20 grs H2O Proposed bullet weight: 128 Measured bullet weight: 129 Proposed i7FF: 0.849 Measured i7FF: 0.773 Proposed G7 BC: 0.326 Measured G7 BC: 0.361 .283 cal (Tockson): Case Length: 1.8898 Base Diameter: 0.473 Case Taper: 0.34 deg Shoulder angle: 25 deg Neck length: 0.241 Rim thickness: 0.054 Rim height: 0.1615 Groove angle: 33 deg Bullet diameter: 0.283 Bullet length: 1.5 Cartridge overall length: 2.8 Proposed case capacity: 49.34 grs H2O Measured case capacity: 50.81 grs H2O Proposed bullet weight: 122 Measured bullet weight: 124 Proposed i7FF: 0.824 Measured i7FF: 0.717 Proposed G7 BC: 0.264 Measured G7 BC: 0.308 CONCLUSIONS: All candidate rounds met the requirements while eking out substantial margins in cost, weight, and recoil versus legacy calibers of comparable capability (e.g., .308 Winchester). No candidates tested showed any concerning deficiencies in critical metrics like penetration, or retained energy. Every single candidate round tested at a lower i7 FF than proposed. No candidate round tested at a higher i7 FF than 0.8. All candidate rounds produced test velocities close to their proposed velocity. Some candidate rounds had marked (>1gr) deviations from their proposed projectile weight, but this was deemed a byproduct of manufacturing and not considered critical. No candidate round had less than 800 yards range with at least 700 ft-lbs striking energy, which is considered exceptional performance, even considering the small caliber of some of the rounds. Pine penetration for all rounds substantially exceeded the minimum specification, indicating suitability for hunting large game at medium to long distances. Trajectory and wind drift for all candidate rounds was excellent. In each metric, the rounds were ranked, shown by the tables below. Velocity: 1. Neelam 2. Griffin (106) 3. Flapper 4. Griffin (85) 5. Curler 6. Tockson Energy: 1. Flapper 2. Griffin (106) 3. Tockson 4. Neelam 5. Griffin (85) 6. Curler Trajectory: 1. Curler 2. Neelam 3. Griffin (85) 4. Flapper 5. Griffin (106) 6. Tockson Wind Drift: 1. Griffin (106) 2. Neelam 3. Flapper 4. Griffin (85) 5. Curler 6. Tockson Pine Penetration: 1. Flapper 2. Griffin (106) 3. Neelam 4. Curler 5. Griffin (85) 6. Tockson Materials Cost: 1. Neelam 2. Griffin (85) 3. Griffin (106) 4. Curler 5. Tockson 6. Flapper Weight: 1. Curler 2. Neelam 3. Griffin (85) 4. Griffin (106) 5. Flapper 6. Tockson Recoil: 1. Curler 2. Griffin (85) 3. Neelam 4. Griffin (106) 5. Tockson 6. Flapper All competitors were very close in all metrics except cost, weight, and recoil. From these, it is immediately evident that the 106gr projectile proposed by Griffin's team was the most cost-effective round of all tested, scoring first or second in all performance metrics besides trajectory, where all rounds were extremely close anyway. In addition, this proposal's projectile possessed several key attributes which were decisive in its selection: A very high sectional density (second-highest among projectiles tested), unprecedentedly low drag, and an economical expanding projectile which remains front-stable during penetration. Most other proposals used steel full metal jackets, or were made entirely of pressed steel, which are designs that, while they provide excellent penetration characteristics, do not remain stable throughout their path and often deviate from the shot line, and which also do not provide any expansion to widen the wound cavity. These characteristics are considered acceptable, but those of an expanding, front-stable bullet are certainly preferred. Griffin's other proposal was an 85gr bullet of novel construction that, while very interesting, was considered far riskier, while possessing less desirable ballistic characteristics anyway. It could, however, form the basis for a promising armor piercing projectile, and so funding for further study of this design is recommended.
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