Hi RecyMech
I was a fitter-gun with LAD 47 Fld Regt, when they had 105 mm Light Guns in the late 70s. I worked on both the L118 (which the regiment was equipped with) and the L119 when 3 Bty borrowed some for a while. The L119 is a different beast compared to the L118. Not only are the breaches different so are the muzzle brakes, and the muzzle brake clamp when towing the gun (due to the shorter barrel). The L118 has an electrical firing box, where the L119 has a firing lever. Sights and things like the air pressure in the recuperator where not the same. I am not too sure if the balance springs were of different length again because of the shorter barrel.
Note about the firing platform. Firing platforms are placed directly on the spot the Battery Surveyor and GPO had selected, the gun is then wheeled on to the platform and fixed by the steel cables to the platform. This ensures the gun remains in the same spot when being given a new target. Not too sure if it is as important today with the on board gadgets but it was when the laying of the gun was done by using the coordinates from the CPO and TARAs in the Command Post it was. Traversing the gun was a lot easier using the firing platform, especially on an anti-tank shoot. I trick of mine was to pick the gun up by the gun spike and traverse it a full 360 degrees on my own. The new gunners to the battery were amazed that the skinny gun fitter could do this, none figured out that I had elevated the gun so it was balanced on its wheels.
The gun could be moved on sort tows using the A frame under the cradle. This was the main support for the barrel when being transported by Puma helicopter. It was introduced when the RAF still had the Wessex. The gun had to be split in two, cradle and recoiling masses in one load and the saddle and trail on the second lift.
To get the gun into the travelling position the right hand wheel had to come off. To keep the gun within the width to load on to one of the then RAF transports the saddle would have come into contact with the wheel when turning the barrel round. The whole trail would have had to be redesigned after the RAF only had Hercules left. I spent most of my time sorting out wheel knock from this wheel and found if the crews kept the face plates of the wheel and brake drum clean then there was less knock. We had some boffins from Woolwich come and investigate the wheel knock with our guns. When I told them that my batteries guns had less knock after we started to keep the face plates clean they poo pooed it and said I was lucky not to have as many problems as others were having. After leaving REME one of the chaps I worked with was in a TA gunner unit and he was moaning to me about the wheel knock so I suggested that they cleaned the face plates. He came back to work after an exercise and said that my method worked.
Lastly personal a note about the ammunition. As I had to be on the gun position when they were firing them I would often join a crew if they were sort of gun numbers. Spending a day lugging the semi fixed US ammo was more knackering than what appeared to be twice the effort with the British separate ammo.
If you feel I might be able to answer any questions please do contact me.