The requirements of a police marksman are very different from those of a military sniper. Most police use of precision fire is at much shorter ranges, usually under 100m. On the other hand the need for accuracy is if anything more pressing. Police have had to shoot criminals that holding on to hostages. If lethal force must be used, it needs to be used with minimal risk to the innocent. Headshots are usually mandatory and over penetration and overshoot are real concerns.
Some police departments are very aware that the 7.62x51mm is too powerful for many of the situations that precision fire is required for. In the past rounds such as the .22 Hornet have been used by some police forces. A more common choice these days is the 5.56x45mm. To reduce range and gain flatter trajectories lighter bullet weights such as the 55gr tend to be favoured over heavier rounds. The 5.56mm is not without its problems, however, and its light bullets can be sometimes prone to insufficient penetration, premature break up and deflection.
Soon after the US adopted the 55gr M193 5.56mm round the UK began to experiment with their own microcalibre round. What was done was rather interesting. Essentially the Brits took the M193 round and increased its sectional density while retaining its original weight. In practice this means that instead of a .224 55gr round they used a .198 56gr bullet. The 4.85mm Experimental Round, as it was to become known, used the same case as the M193, although in the final round case length was increased from 44mm to 49mm.
There have been many attempts to create the ideal military rifle round. What exactly constitutes ideal has varied. Engineers working after the Second World War were using different criteria to their Victorian and Edwardian counterparts. As I discuss elsewhere, the quest for the ideal military rifle round is in actuality a false trail, the real requirement being a machine gun round that also performs adequately in assault rifles. Of the various microcalibre solutions tried, the 4.85mm probably came the closest to being an ideal rifle round.
One of the things that contributes to accuracy is a short time of flight (TOF). The less time a bullet takes to reach a target, the flatter its trajectory. Shorter flight time means a moving target needs less lead. Shorter flight time also means less time for the wind to push the bullet off course.
To reduce flight time a bullet not only needs a high initial velocity but must keep this velocity. Retaining velocity is determined by the bullets aerodynamic shape and its weight, and this is expressed by its ballistic coefficient. One of the things that contributes to a good ballistic coefficient is a good sectional density. The effect of this can be seen when the performance of the 4.85mm was compared to the M193 which had a similar weight and velocity, but lower sectional density.
The 4.85mm cartridge was based on a lengthened (49mm) and necked-down 5.56 case drawn with a 23-degree shoulder. The .19 caliber pointed boattail bullet weighed 56 grains. It had a lead core and a copper-washed steel jacket. Velocity from a barrel with a fast 1.5 twist was 3,117 fps.
Because of its excellent sectional density, the 4.85mm bullet proved to have superior penetrating qualities when tested against American 5.56 M193 ball ammunition. During the final NATO trials at Meppen, Germany, the 4.85mm bullet at a range of 550 meters, penetrated a German steel helmet and NATO 3.4mm mild-steel plate. The 5.56 M193 round utterly failed to penetrate the helmet, succeeding only to crack it at 475 meters.
NATO instead adopted an improved version of the 5.56mm, the 62gr SS109, which is known in American service as the M855. The M855s longer range and lower velocity make its use as a police precision round questionable. This article on the Firearm Blog shows that the 4.85mm was ballistically superior to the M855 too.
James Leahy of James Callhoon Mfg became interested in the British experiments and has produced a series of bullets based around a .19 calibre projectile. The round that interests us is the .19-223 aka 19-223 Calhoon, which is based on a 5.56mm/.223 case. Unlike the British round Calhoons version has a 30 degree shoulder and a 44mm case length.
|Bullet weight/ type||Muzzle Velocity||Muzzle Energy|
|32 gr. (2.1 gm.) HP||4,100 ft/s (1,200 m/s)||1,194 ftlbs (1,619 joule)|
|36 gr. (2.3 gm.) HP||3,800 ft/s (1,200 m/s)||1,154 ftlbs (1,565 joule)|
|40 gr. (2.6 gm.) HP||3,700 ft/s (1,100 m/s)||1,216 ftlbs (1,649 joule)|
|44 gr. (2.9 gm.) HP||3,600 ft/s (1,100 m/s)||1,266 ftlbs (1,716 joule)|
Some calculations of sectional density prove interesting. A 55gr 5.56mm round has a sectional density of around 0.157. A 44gr .19 bullet has a sectional density of 0.160 but has a 400+fps advantage in velocity. Calhoon doesnt appear to currently offer .19 bullets heavier than 44gr, but a 56gr bullet at 3,117fps mimicking the 4.85mm Experimental would have a sectional density of 0.204, very close to the .221 of a 146gr 7.62mm NATO round at 2,756fps. A 50gr .19 round would have a sectional density of 0.182, exceeding the 0.177 of the M855.
It is pretty clear the .19-223 offers shorter flight times, better penetration and flatter trajectories than the 5.56mm. Zeroed to 100yds the 44gr at 3,600fps has a mid-range trajectory of less than an inch and falls 1¾ at 200yds.
For police marksman use of the 19-223 seems to have much to recommend it. It will shoot flatter than a 5.56mm or 7.62mm without the excessive range of heavier bullets. Its penetration performance is better than that of 5.56mm round of similar or even heavier weight and the bullet has sufficient size and energy to be effective when used for head shots. Existing 5.56mm weapons can be adapted to its use with just a barrel change. The smaller calibre of the round will mean the barrel walls will be thicker than those of a 5.56mm barrel for the same external dimensions. Thicker barrel walls mean a more rigid barrel and this is likely to contribute to increased accuracy.
Cartridges of the World, 12th Edition, Gun Digest Books, page 164, comments about the 19-223:
It offers less recoil and a flatter trajectory than the .223 Remington, and is a superb long-range, flat shooting varmint cartridge with abundant terminal energy.
Hunters report the .19-223 to be highly effective against animals such a coyote and that it has the added advantage that the small entry wound causes little damage to the pelt.
According to the Wikipedia Article on the .22-250: Both the British Special Air Service and the Australian Special Air Service Regiment used Tikka M55 sniper rifles chambered in .22-250 for urban counter-terrorism duties in the 1980s, in an attempt to reduce excessive penetration and ricochets.
By the Author of the Scrapboard :
Attack, Avoid, Survive: Essential Principles of Self Defence
Available in Handy A5 and US Trade Formats.
Crash Combat Second Edition with additional content.
Epub edition Second Edition with additional content.
Crash Combat Third Edition
Epub edition Third Edition.