November 3, 2015:
South Korea recently sold a hundred of its locally designed and made K9 155mm self-propelled howitzers to India for about $7.5 million each. South Korea has already sold 350 K9s to Turkey and 120 to Poland. While superficially similar to the American M109 the K9 is a heaver (46 tons versus 28 for the M109), carries more ammo and has twice the range (up to 56 kilometers in part because of a barrel that is a third longer). There is more automation on the K9, so it has a crew of five versus six on the M-109. South Korea thus joins Germany in their effort to build a suitable replacement for the elderly M109 design. To get the Indian sale South Korea had to agree to have the K9s assembled in India from South Korean components. This sale gives South Korea an edge in obtaining an even larger contract to supply India with several thousand towed 155mm howitzers. Because of corruption and political problems the Indian Army has not been able to buy any new artillery since the 1980s. The chief competitor for the Indian contract was Russia which offered its similar 42 ton 2S19. The K-9 won on the basis of technical capabilities, field tests and a South Korean reputation for quality and reliability.
The K9 and 2S19 are examples of the kind of system the United States sought to build to replace its 1960s era M109. The United States sought to build the 56 ton Crusader to replace the M109s. Crusader was very similar to the K9 but was too complex and expensive and the heavier weight was seen as a disadvantage for a country that has to ship its armored vehicles overseas to use them. For South Korea, Turkey and Poland that is not a problem and more heft (and protection for the crew) is an advantage.
One American innovation K9 users will probably adopt is the GPS guided Excalibur shell. This smart shell entered service in 2008 and changed everything. Excalibur has worked very well in combat, and this is radically changing the way artillery operates. Excalibur means 80-90 percent less ammo has to be fired to destroy a target and this results in less wear and tear on SP artillery, less time needed for maintenance, and less time spent replenishing ammo supplies and more time being ready for action.
Because of Excalibur (and other precision munitions) since 2001 operations in Iraq and Afghanistan provided very little work for the M109. The lighter, towed, M777 has proved more useful, especially when using the Excalibur shell. Currently, the army plans to keep newly upgraded versions of the M109 around until 2050. The army plans to acquire at least 551 upgraded M-109s by 2027, reflecting the impact of the Excalibur shell, and the number of older M109s that are still fit for service. The M109 was a solid design, which is pretty clear from how difficult it's been to come up with a replacement. So, in the end, the army replaced the M109 with another M109 upgrade and is still seeking a replacement for that.