http://www.army-guide.com/eng/product3729.html
The main change on the M109L is the replacement of the existing 23 calibre barrel with a 39 calibre barrel. Externally this is configured to the M109 mounting, but internally it is ballistically similar to the FH-70 configuration and can thus fire existing M107 ammunition or FH-70 ammunition. Firing L15 HE projectiles the M109L has a maximum range of 24,000 or 30,000 m with assisted ammunition.
In addition to the installation of a new ordnance, the following have been modified:
(1) recoil buffers and run-out buffer
(2) cradle to fit the new ordnance
(3) replacement of the equilibrator and elevating cylinder
(4) barrel clamp to fit new barrel.
The new 155 mm 39 calibre barrel is fitted with a revised muzzle brake, with the maximum recoil increase on the M109L being only 100 mm. The existing breech and breech ring of the original M109 have been retained.
The elevating mass, as modified, is interchangeable with that on the basic M109, furthermore the mechanical interface between the elevating mass and saddle, as well as the mountings of the optical device, do not require any modification.
To reduce operator fatigue and increase rate of fire, a rammer can also be fitted to the M109L system.
