A new handgun has reignited the debate over which type of bullet is best: small and fast, or big, heavy, and therefore, slower. The MP7 personal defense weapon (PDW) seems to embody the small and fast paradigm. Devised by Heckler & Koch Inc., (www.hecklerkoch-usa.com), it fires a 4.6 30-mm round (equivalent to .18 caliber) weighing about 26 grains. It leaves the muzzle at 2,461 fps and has a maximum effective range of 200 m, according to H&K. But the arms maker also manufacturers a submachine gun, the UMP45, that falls firmly in the other school. The gun fires 230-grain .45-caliber bullets that leave the muzzle at 853 fps. Each side has points in its favor. But is one bullet really best?
Some weapon experts insist bigger bullets are better because they are more likely to hit a vital organ, the central nervous system, or a large bone, and bring an opponent to a halt. They also say the greater mass of the bullet lets it carry more kinetic energy and momentum, other factors in downing an opponent. Just comparing cross sections, a .45-caliber round creates a 0.16-in.2 hole, while the .18 caliber round leaves just a 0.025-in.2 hole.
The difference becomes greater with soft and hollow-point rounds that expand inside the target. "That's why police in the U.S. use controlled expansion ammo," says Neil Burchel, leader of the Army's Medium Machine Gun team within TACOM, Rock Island, Ill. "They dump all their energy in the target and don't overpenetrate or harm people on the other side of the target."
A .45 hollow-point can expand to 0.5 in.2, while PDW rounds don't expand at all. This means a .45 round destroys up to 20 times as much tissue as a .18 PDW bullet.
Frangible rounds that burst apart inside the target provide the ultimate stopping power and tissue destruction, but are outlawed by the Geneva Convention.
The main reason for faster, therefore lighter, bullets is to overcome body armor, which has become commonplace in modern armies. "A Kevlar vest will stop most older small-arms rounds," says Burchel. "But you can take an ice pick and drive it right through the vest. Turns out, the smaller and faster the round is, the better its chances of defeating Kevlar, titanium sheets, or even homogenous armor on tanks. That's why modern antitank rounds are long-rod penetrators. They are very thin, travel extremely fast, and go through tank armor like it's butter."
The MP7 round, for example, was designed in conjunction with the weapon to defeat the NATO's Crisat test target, 20 layers of Kevlar covered with 1.6-mm titanium plate. Crisat simulates Soviet-style body armor. And indeed, the MP7 4.6-mm steelball round goes through a Crisat target at 100 m, and defeats two such targets at 50 m. H&K provides other types of ammo for the MP7, including blanks, tracers, frangibles, and low-cost training rounds.
Another factor in going to lighter bullets is to reduce recoil and make the entire gun lighter and less bulky, which should make the weapon more accurate. After all, it doesn't matter what kind of bullets are fired if they don't hit the target.
Recoil on the MP7 is 50% that of a 9-mm NATO round, and the folding stock allows shoulder-firing it like a rifle, which also improves accuracy. And the weapon sports a 7-in. barrel, longer than those on most other handguns. Longer barrels translate into more accurate, consistent shooting. The gun is also lighter and easier to carry in a holster than other handguns and pistols, so a person is more likely to carry it while doing other duties.
WHAT'S THE TARGET?
In the end, it's the target and situation that determines the best bullet or gun. Will action be at close quarters or will targets be hundreds of meters away? Will dedicated warriors fire weapons or will ancillary support staff with little weapons training? And are targets wearing flak jackets and helmets or ordinary clothing?
"If you are shooting at a soft target, such as Taliban who don't wear bullet-proof vests, small, high-velocity rounds will give you over-penetration," says Burchell. "You may put a tiny hole in the person, but if you don't strike something vital, that person will continue fighting.
"There have forever been arguments among firearm enthusiasts about whether a 9-mm round is better than a .45," says Burchell. "Newer rounds that are smaller but faster, it seems, will continue that debate."