Search for a quieter varmint cartridge By tloC54 Attributions Portions Copyright © AmmoGuide.com, used with permission Charts and graphs generated using Helge Peters’ Ballistik shareware Thanks to Homer Powley for the equation behind Computer for Handloaders Thanks to Doug Owen and Mike Haas for suggestions without which the goals and conclusions of this paper might not make much sense All rights reserved Goals The goal of this paper is to find or create a cartridge which will have the drop and wind resistance of a 221 Fireball but which will generate no more noise than a 22 Hornet and also will not move a 12X scope completely off the target upon firing. Desirables Certain desirables are known a priori. A longer barrel will move the muzzle blast farther from the shooter’s ears. Sound falls as the square of the distance. Small case capacity and consequent small powder charge will provide less of what makes the noise in the first place (smaller noise). Lower pressure (arbitrarily 45,000 psi) combined with high expansion ratio will result in lower pressure at the muzzle for a less-sharp noise. Similarly, a faster powder will reduce muzzle pressure. Supersonic bullet noise is distributed over the flight path and is therefore a small component of noise at the ear so bullet velocity won’t be a factor. A look at some existing cartridges 17 HMR 17 grain V-Max, BC = .122 The .17 Hornady Magnum Rimfire (HMR) cartridge was introduced in 2002, designed to offer varmint and pest hunters a faster, flatter rimfire round than the .22 Winchester Magnum Rimfire. The .17 HMR is based on a neck-reduced .22 WMR case. Accordingly, owners of .22 WMR firearms should find conversion to the .17 HMR a simple matter of a new barrel. The higher muzzle-velocity of the .17 HMR combined with more efficient bullets yields a potent round out to 200 yards or so, far exceeding the range of the .22 WMR. Its higher ballistic coefficient means less drop. Its shorter time-in-flight translates directly into less wind deflection. The light, high velocity bullet is also less prone to ricochet. Hornady 17 grain bullets leave the muzzle at 2550 fps. Rifles are available from Ruger, Marlin, Volquartson, NES and others and .17 HMR handguns are also on the market. 22 WMR Introduced in 1959, the .22 Winchester Magnum Rimfire (WMR) is an improved version of an earlier Winchester cartridge, the .22 Winchester Rimfire (WRF). In fact, .22 WRF ammunition may be used in .22 WMR firearms, but the reverse is not true. The .22 WMR is far more powerful than any other currently offered rimfire cartridge, and even exceeds the performance of some of the early .22 centerfire rounds. To quote Cartridges of the World, 7th Edition: "Its ballistics in a 6-inch pistol barrel exceed any other rimfire fired from a rifle" Often, .22 revolvers are sold with 2 cylinders, one for conventional .22 rimfire ammunition, and another for .22 WMR, greatly contributing to the versatility of those handguns. The .22 WMR enjoys a good range of bullet styles, from hollow-point to full jacketed configurations, providing good coverage from varmint to small game, with an effective range out to 125 yards. Currently published factory muzzle ballistics for rifles include a 40-grain bullet at 1,910 fps and 324 ft-lbs. of energy, and pistols (6.5-inch barrel) at 1,480 fps/195 ft-lbs. 22 Hornet Sierra #1210 45 gn Hornet BC = .137, 2000 to 2700 fps Sierra #1455 55 gn BlitzKing BC = .264, 2550 to 3100 fps The .22 Hornet began as a wildcat cartridge in the 1920s. It was developed by Col. Townsend Whelen, Captain G.L. Wotkyns and other researchers at the Springfield Armory, using 1903 Springfield and Martini single-shot rifles for testing. In 1930, Winchester added the .22 Hornet to its product line, ending its days as a wildcat. The .22 Hornet has enjoyed a strong, almost exclusive association with bolt action and single-shot rifles. Accordingly, it earned a reputation for superb accuracy, despite the eventual emergence of both .223 and .224 diameter offerings. For best results, it is prudent to match bore and bullet, but excellent results can be had regardless. The Hornet has also been popular in certain handguns, such as the Thompson/Center Contender. Equally at home in rifle and pistol, the Hornet is a surprisingly versatile cartridge, as the reloader can easily duplicate ballistics of the .22 rimfires, magnum or otherwise. The .22 Hornet propels a 46 grain bullet at 2690 fps with 739 ft-lbs of muzzle energy. 22 Hornet 221 Fireball Sierra #1455 55 gn BlitzKing BC = .264, 2550 to 3100 fps 221 Fireball 222 Rem Mag Sierra #1455 55 gn BlitzKing BC = .264, 2550 to 3100 fps 24” BBL, 25 of 3031, 3300 fps 222 Rem Mag 220 Swift Sierra 9390 80 gn HPBT MK BC= .420 The .220 Swift was introduced by Winchester in 1935 in the Model 54 bolt-action rifle. It was a notable event, being the first factory cartridge to exceed 4000 feet-per-second. When the Model 54 was discontinued 2 years later, the Swift went on to be chambered in the successor Model 70 and became popular. While not encountered frequently today, the Swift holds on to its reputation for high speed, as few cartridges have attained its velocities. In its day, the Swift weathered unjust charges of wearing out barrels faster than other cartridges (it did not) and being ineffective on large game (it never should have been used on large game in the first place). In 1964, Winchester discontinued this exceptionally flat- shooting varmint round, replacing it with the .225 Winchester. 220 Swift ============================================ 6x45 (6mm-223) Sierra #1502 55 gn BlitzKing BC = .225, 2950 fps on up Sierra #1507 70 gn BlitzKing BC = .299, 2600 fps on up The 6mm-223 Remington, also known as the 6x45mm, came into being in late 1965, shortly after Remington introduced the .223 Remington as a sporting round. Various experimenters built rifles for this cartridge for benchrest or varmint shooting. Jim Stekl, then manager of Remington's custom shop, set an IBS 200 yard Sporter aggregate record of .3069 MOA in 1973 using the 6x45mm. For a time, some owners of AR-15 rifles rebarreled their rifles to this caliber for use in NRA National Match Course competition. However, the 6x45mm can not compete successfully with the 7.62x51mm NATO (308 Winchester) round at ranges beyond 300 yards. After its brief flurry as a benchrest and match cartridge, the 6x45mm has now been relegated primarily to the varmint cartridge role, used by those who want more power than the .223 with the added advantage of being able to use cheap military brass for forming cases. Reloading dies are available from RCBS and chambering reamers from Clymer. 6x45 (6mm-223) with 55 grain bullet 6x45 (6mm-223) with 70 grain bullet 6x47 Sierra #1502 55 gn BlitzKing BC = .225, 2950 fps on up Sierra #1507 70 gn BlitzKing BC = .299, 2600 fps on up Introduced in the early 1960s, the 6x47mm was intended as a benchrest cartridge that would equal the accuracy of the best .22 caliber cartridges as well as take advantage of a rapidly expanding market of highly efficient 6mm bullets. The preceding decade had brought a shift of popularity from .25 caliber rounds to the 6mm bore, starting with the .243 Winchester in 1954, and the American shooting public was far from satiated in its pursuit of this caliber. The 6x47mm was formed by expanding the neck of the .222 Remington Magnum to accept .243" bullets, benefiting from the greater ballistic coefficients enjoyed by 6mm vs. 5.56mm bullets of the day. The .222 Remington Magnum had been developed as a military cartridge in competition to become the M16's standard chambering and had sufficient case volume to support a larger bullet. The 6x47mm performed well but had its detractors, most of whom complained that the round was "finicky" and hard to "tune in". Ultimately, like most 6mm wildcats of the period, the 6x47mm would take a backseat to the 6mm PPC when it appeared and began to dominate the benchrest field. 6x47 charts are similar to those of 6x45 6 mm Remington Sierra 1530 85HPBT BC .282 The .244 Remington was introduced in 1955, the same year as its main competition, the .243 Winchester. In the next few years, the .243 would establish a strong foothold with the American public while the .244 would struggle. The most-often suggested reason is that Winchester wisely provided a 1-in-10" twist for the rifling of the .243 barrels, which worked with all available bullets. Remington, however, used a 1-in-12" twist for the .244, which could not stabilize the heaviest bullets (over approximately 90 grains). In 1962, Remington re-released the same cartridge as the 6mm Remington (there is no dimensional difference) but now specifying a faster rifling twist to even the field. Some "re-marketing" success has been achieved as the 6mm Remington has established a significant following. 6 mm Remington 25-20 WCF ====================================== .25 TCU Sierra #1600 75 gn Hollow Point BC = .189, 2600 fps on up Sierra #1610 87 gn Spitzer BC = .293, 2800 fps on up Note: 14” barrel The .25 Ugalde / .25 Thompson/Center Ugalde, was developed by Wes Ugalde of Fallen, Nevada, about 1987. Like the other TCU cartridges, the .25 TCU is based on a necked-up and improved .223 Remington case. Original testing by Dean Grennell was described in the August, 1988 issue of Gun World using a Thompson/Center single shot pistol with a 14- inch heavy barrel made by Wes Ugalde.