Although the U.S. Army began replacing the M203 40mm grenade launcher with the M320 in 2009 progress has been slow. Many soldiers still prefer the older M203. The other services are still buying new M203s and the manufacturer has made some popular improvements to the elderly M203 design which keeps it popular with many army troops as well. Part of that continued popularity is the fact that the M203 is ten percent lighter and more compact. However the new M320 was popular when it was introduced and named one of the top ten new systems for 2010. There was one complaint, however. When not attached to the rifle the M320 was simply carried via a sling and got bounced around a lot. Because the M320 had more features and gadgets included there was more stuff that could get broken. After years of troop complaints the army is finally developing a “holster” for the M320.
The M203 was a big breakthrough because it was a 40mm grenade launcher designed to fit under the barrel of the M16 rifle (and similar weapons). Before that the only way to fire these popular 40mm grenades was with a separate weapon (looking like a large, single shot shotgun). The M320 is similar to the M203, but is easier to use, has its own pistol grip, is more accurate, can use more powerful ammo and can be used separately from an M16 with the addition of a stock.
The biggest improvement with the M320 was its sighting system, which featured a laser range finder. At night, an infrared range finder enables a soldier wearing night vision goggles to see the light beam. In over a year of testing, the M320s sighting system was seen to make the weapon much more accurate than the older M203. This was particularly the case with new users. With the M203, you got better after you had fired a hundred or so rounds. That took time, and was expensive (the 40mm grenades cost over $30 each). The 40mm grenades weigh 545 grams (19 ounces) each and have a range of about 400 meters. The grenade explosion can kill within five meters, and wound up to ten meters or more.
What the U.S. actually did was adopt a version of the German designed AG36 40mm grenade launcher, as the M320. The British did the same, calling their version the L17A1. The German developer and manufacturer of the AG36 is now the main producer of the M320.