The M109 is an American 155 mm turreted self-propelled howitzer, first introduced in the early 1960s to replace the M44. It has been upgraded a number of times, most recently to the M109A7. The M109 family is the most common Western indirect-fire support weapon of maneuver brigades of armored and mechanized infantry divisions.
M109A6
Early M109 howitzer of the Royal Netherlands Army.
Open breech of a M109A5 howitzer
United States Army M109A1 howitzer in 1982.
155 mm is a NATO-standard artillery shell caliber that is used in many field guns, howitzers, and gun-howitzers. It is defined in AOP-29 part 1 with reference to STANAG 4425.
M107, M795, M483A1 155 mm projectiles
M107 projectile 155 mm projectile being loaded into an M777 howitzer