I present my own cartridge in this competition, the .224 Zoomer Magnum, also known as the 5.7×47mm. In order to increase the number of rounds that each individual Sioux Scout can carry, I felt that a small caliber, high velocity cartridge would be in order, one that would have light recoil while also meeting (if not exceeding) the requirements set forth. I originally started off with a 1.775" case length (said case was designated as "No. 1"), but the case capacity was found to be woefully insufficient for the desired muzzle velocities. A second cartridge case (designated "No. 2"), with the length increased to 1.875", was found to be just the right amount of capacity needed. Two projectiles were also to be designed. The Type A projectile would be lead-cored with a thick, gilding metal clad steel jacket to prevent fragmentation in soft tissue, enhancing its penetration and preventing lead contamination in wild game taken as food. A small cup would seal off the lead core to prevent it from being squeezed out of the base of the projectile. A more ambitious, cost-reduced Type B projectile was also conceptualized, consisting of a gilding metal clad steel jacket, a mild steel core, and an overall reduced weight compared to the Type A. However, the Von Karman ogive required for this projectile proved to be an real pain in the ass to model with what limited tools were available, and for the sake of my own sanity, the Type B was dropped in favor of the tangent-ogived Type A.
Type A projectile, cross-sectioned. Projectile weight was calculated to be 79.5 grains, with a G7 BC of 0.265. Note the metal cup sealing off the lead alloy core.
Complete cartridge, Type A projectile, No. 2 case. The case itself is lacquered steel. Total cartridge weight is approximately 13.66 grams, and the total materials cost is about 5.04680378 cents.
Load data. Recoil is approximately 3.38 ft-lbs from a 10 lb weapon.
External ballistics, with nominal muzzle velocity. Penetration into pine is approximately 16.52 inches at 600 yards, rounded down to the nearest hundredth of an inch.
External ballistics, with muzzle velocity reduced by 200 ft/s. Penetration into pine is approximately 15.40 inches at 600 yards, rounded down to the nearest hundredth of an inch.