Many countries with tiny defense budgets and no real need for the latest high-tech stuff are finding older weapons, often World War II (1939-45) era stuff, still gets the job done. Some of these older weapons are brought back into service because they are still available, very cheap and get the job done. Thus World War II era aircraft and armored vehicles, some of which served until the end of the century, but by then had become too expensive to maintain. Obtaining spare parts was especially difficult. Firearms have far fewer problems and many of them are still in service.
One of the more recent revived World War II weapons is the American M3 .45 (11.4mm) submachine gun (nicknamed the “grease gun”). It was quickly developed in 1942 to give American troops something similar to German 9mm and Russian 7.62mm submachine guns. Everyone seemed to have a submachinegun except the Americans. Actually the United States had developed an 11.4mm Thompson submachine gun for World War I but this weapon arrived too late to see combat in World War I. The M3 was a hurried upgrade of the Thompson that saw service in 1944 and 1945. Only about 700,000 were made. They were cheap, costing less than $300 (in 2016 dollars) to make and very durable. The M3 weighed 3.61 kg (8 pounds) empty and had a 30 round detachable box magazine. Rate of fire was 450 rounds a minute (7.5 a second). Thus each magazine provided 4-5 short bursts of fire. Effective aimed range was about a hundred meters. Each loaded magazine weighed 955 gr (2.1 pounds).
With all that in mind the Philippines Navy reintroduced the M3 in 2004, mainly for use by boarding parties. These M3s were fitted with a suppressor (to keep the flash down in dark areas inside a ship) and a Picatinny rail for mounting night sights or modern close range aiming deices and flashlights. The compactness of the M3 was a big plus. The M3 was 579mm (23 inches long) and fired a heavy, hard hitting round. Just what you need if there is trouble inside a ship. The U.S. also recognized these features and kept using the M3 until 1992.
This type of weapon, called the submachinegun, is popular with police, gangsters and those who make violent movies and TV shows. Equipping troops (especially infantry) with lightweight automatic weapons began as a German innovation during World War I (1914-18). In doing that, the Germans also took the lead in developing submachineguns, like the MP 18, a weapon that would eventually evolve into the modern assault rifle. By the end of World War I, about 30,000 MP 18s were in use. The MP 18 demonstrated the devastating effect of automatic weapons in the hands of infantry. The MP 18 fired the standard 9mm pistol round at the rate of 6-7 bullets a second, and used a 32 round drum magazine. The basic need was for a compact weapon that could quickly fire a lot of bullets to deal with an emergency situation, like a trench full of armed and angry enemy troops. This gave the MP18 user a big edge in combat. The Germans kept developing this type of weapon and by World War II they had the MP 38 and MP 40. The short range (50-100 meters) of the 9mm pistol round prevented the Germans from attempting to rearm all their infantry with this weapon, because the troops often had to hit targets farther away.
It wasn't until they saw the Russians use similar weapons on a mass scale during World War II that the Germans realized that the short range of the 9mm pistol round was not as great a shortcoming as they thought. The Russians understood that for an attack, arming all the troops with submachineguns gave you so much firepower that the enemy had a hard time shooting back at your advancing infantry. This was particularly useful in urban or trench warfare, where there were a lot of small scale (a dozen or fewer attacking troops) operations at short ranges.
Russia produced over five million of their 3.6 kg (8 pound) PPSh submachineguns. It used either a 35 pound box magazine (weighing 680 grams/1.5 pounds) or a 1.8 kg (four pound) drum holding 71 rounds. That was 7-8 seconds worth of firing. The bullet used was a 7.62mm (.30 caliber) pistol round that moved at only about 516 meters (1,600 feet) per second. Catch one of these in the head and you were dead. Anywhere else, and you would probably live. But with so many of these bullets flying around, multiple hits were more likely.
It’s not just old automatic weapons that are still in use. Police and paramilitary forces in poor areas of the world still use one of the first modern infantry rifles; the single-shot Lee-Enfield. This bolt action rifle is adequate for arming local voluntary security units. Since many of these volunteers belong to tribes out in the countryside, they like having a fine, if elderly, hunting rifle like the Lee-Enfield. Many other countries still have lots of Lee-Enfields which police like to use as a sniper or sharpshooter weapon.
The Lee-Enfield is one of the oldest, and still widely used, rifles on the planet. Over 17 million were manufactured between 1895 and the 1980s. While there are more AK-47s out there (over 20 million in private hands), these are looked down on by those who use their rifles for hunting, or killing with a minimum expenditure of ammunition. The 4 kg (8.8 pound) Lee-Enfield is a bolt-action rifle (with a ten round magazine) noted for its accuracy and sturdiness. The inaccurate AK-47 has a hard time hitting anything more than a hundred meters away, while the Lee-Enfield can drop an animal, or a man, at over 400 meters.
There are millions of Lee-Enfields still in use throughout India, Afghanistan, Pakistan, and even Iraq and other Persian Gulf nations. These are largely World War II leftovers. In the early half of the 20th century, the British gave out millions of these weapons to allies, or those being courted. Noting the accuracy of the Lee-Enfield (.303 caliber, or 7.7mm), the locals came to prize the rifle for hunting, and self-defense. There are still many gunsmiths throughout the region (and at least one factory in India) that will refurbish century old Lee-Enfields to "like new" condition. Ammunition is still manufactured, with the high quality stuff going for a dollar a round, and lesser quality for 25 cents a round. These rifles sell in the west for $500-1,000. Non-firing replicas can be had for a few hundred bucks, and for about twice that you can buy deactivated (cannot be fired) originals. So the Lee-Enfield will carry on well into the 21st century.