The U.S. Department of Defense recently revealed that a U.S. Marine artillery battalion (1st Battalion, 10th Marines) fired more rounds (35,000) in a single campaign (Syria June-October 2017) than any American artillery battalion (army or marine) since the Vietnam War. The individual marine 155mm howitzers also fired more round per gun and fired the largest number of GPS guided rounds per gun in one campaign. Moreover, there were never more than six of the marine 155mm howitzers in action at any one time.
The marines rotated artillery batteries in and out of Syria to allow for maintenance on the guns and rest for the crews. During the five months of the fighting, the Marines were mainly supporting Kurdish led rebels fighting to take the ISIL (Islamic State in Iraq and the Levant) capital of Raqqa. Thus each of the marine 155mm guns averaged 39 155mm rounds a day. But the marine 155mm howitzers fired over a hundred rounds on some days and only a few on others, usually on days they were changing position to keep up with the Syrian rebels.
A Marine Corps battery (six guns) of M777 155mm howitzers was sent to Syria in early 2017 to support the SDF Kurdish militia as it advanced towards the ISIL capital of Raqqa in eastern Syria. The marines fired a lot of M1156 GPS guided shells and often did so at extreme ranges. In the course of the five months, the marines wore out the barrels on two of their howitzers. Normally the M777 barrel can fire up to 2,500 shells before wearing out but barrel life depends on what type of shell your fire. If you fire the longer range shells (which the Marines did) barrel life is much reduced (to about a thousand rounds). While the GPS guided shells reduced the need for firing a lot of shells, the Americans also noted that fewer howitzers were required to provide accurate artillery support when using GPS guided shells and even in Afghanistan some isolated artillery units (usually a battery or just a section of two guns) fired a lot of GPS guided shells and provided timely and accurate fire often at extreme range.
At some points during the Raqqa campaign, the marines fired non-GPS shells at area targets (where GPS precision was not a factor) to pin down the enemy forces and prevent them from moving. In Syria, the marine 155mm howitzers, which can be moved (via a sling) by a helicopter, often operated in smaller detachments (usually two guns) to provide support for more rebel units. Most of the fighting inside Raqqa did not require the 155mm guns (and the tons of ammo they had to have with each gun) to be dispersed. The marine 155mm shells provided most of the firepower for the battle of Raqqa because airstrikes delivered less than half as many smart bombs and missiles compared to the marine artillery shells fired.
Releasing the data on the number of 155mm shells fired by this one marine artillery battalion revealed that the battalion fired more rounds than were fired during the 2003 invasion of Iraq (when many more 155mm howitzers fired 34,000 rounds or 261 rounds per gun). In 1990-1991 campaign to drive Iraqi troops out of Kuwait 730 army and marine 155mm howitzers fired 50,000 rounds, or 69 rounds per gun. In both those campaigns, no single battalion (each of 18 guns) fired more than a few thousand rounds.
The marine artillery effort in Syria also demonstrated the sturdiness and reliability of the M777 towed 155mm howitzer. The manufacturer has use and maintenance data from the Syria operation and with that can make more improvements. To deal with the barrel wear problem a new full-bore chrome-lined barrel had already been developed. This more expensive barrel lasts about 50 percent longer than current howitzer barrels. The marines were only scheduled to get about a hundred of the new chrome lined barrels but the Department of Defense is re-thinking that because the marine M777s most frequently end up in situations like the Raqqa campaign. The marines were to receive their first chrome lined barrels in 2019 but that may happen sooner.
All this is the price of progress. In 2007 the U.S. Army and Marine Corps received their first M777A1 lightweight 155mm howitzers. The M777s cost $1.9 million each and the U.S. has bought about a thousand of them so far, for use by the army and marines (who received nearly 400 of them). The manufacturer, BAE, has also received a contract to refurbish dozens of M777s that returned from service in Afghanistan. This cost $91,000 per howitzer. Many of the M777s used in Syria will undergo refurbishment because of such heavy use during a short period.
The British designed howitzer is also used by Canada and Britain. The army uses M777s in airborne and Stryker brigades while for the marines all their field artillery is towed. A five ton truck is used to tow the guns, but a special, 4.5 ton LWPM (Lightweight Prime Mover) is available to do that as well. The M777 is, at four tons, the lightest 155mm towed howitzer ever fielded. A crew of five fires regular rounds to 24 kilometers and RAP (rocket assisted projectiles) rounds to 40 kilometers. M777 fire control is handled by a computerized system that allows faster response time and more accurate shooting. Even before the Syria operation users reported that the M777 was accurate and reliable.
All this played a large role in the heavy use of the M777 in Syria. Most of the fire missions were called in by American fire control teams attached to the rebel units. These forward observers used GPS and laser range finders (usually combined in one binocular-like device) to provide the marine artillerymen with a precise location of the target. Inside Raqqa the targets were often small and close to friendly troops. While a "dumb" artillery shell will land within 75 meters (more or less depending on range) of the aiming point, the GPS guided one lands within a ten meter (31 foot) circle around the aiming point. In Raqqa if the troops were facing a small target (like one or more snipers in a building), two GPS guided 155mm shells fired nearly simultaneously (from up to 40 kilometers away) would usually eliminate the problem. This not only speeds up the conquest of Raqqa but kept casualties down among the attacking troops. This does wonders for morale and keeps your most experienced troops in action until the battle is won.