Here is some data on the guns taken to Spain by the French.
For the Army of the Coast of the Ocean, Napoleon ordered on 18 February to organise three artillery trains at Bayonne using each of, 4x 12-pdr, 4x 8-pdr, 6x 4-pdr, 4x howitzer using the guns the storehouses and arsenals of the Empire. 400 train horses were attached. The 12-pdr and 8-pdr were to have double ammunition allocations and the 4-pdrs triple. The personal for the train was to come from the 6e bis compagnie train d'artillerie.(Clarke to Gassendi 20th February 1808)
A siege train comprising 12x 24-pdr short with 500rounds per gun, 12x 168mm howitzers with 500rounds each and 6x 220mm mortars again with 500rounds are listed in August 1808 as in service in Spain (Clarke 18th August 1808). Of these guns, 5x short 24-pdrs being used in the siege of Madrid in December 1808 (kellerman 21st December 1808).
The new year of 1809 saw a new siege train being prepared for service in Spain, consisting of 12x 24-pdr short, 6x 220mm mortars and 6x 324mm mortars Clarke 11 Jan 1809). King Joseph's Army had 12x 24-pdr short drawn by oxen for the lack of horses (clarke 11 Jan 1809).
After the Siege of Ciudad Rodrigo 10 July 1810 (Ciudad Rodrigo fell to the French on 10 July 1810, after being under siege of 72 days), the following ordnance was in action, some of which had been fired beyond a point of safe use: 10 24-pdr, 7 16-pdr (1 consumed), 12 12-pdr (1 consumed), 8 Howitzers, 4 12-pdr mortars, 3 8-pdr mortars, 4 6-pdr mortars and 2 Perriers.
At the first Siege of Saragosa (June to August 1808), 6x 16-pdr, 6x 12-pdr, 12x 8-pdr, 4x 4-pdr, 8x 220mm howitzers, 8x 168mm howitzers and 5x 324mm mortars were used. The only siege guns being the 220mm howitzers, the 324mm mortars and 16-pdr (reintrodcued to the army in 1807). For the second siege 6x 24-pdr were added to the siege train. 4th January 1809 at the second siege of Saragosa, 6x 24-pdr, 6x 16-pdr, 10x 12-pdr, 6x 168mm howitzers, 4x 220mm howitzers, 2x 220mm mortars and 6x 324mm mortars being used3. It is likely that the 8-pdr and 12-pdr were field pieces as no long 12-pdr or 8-pdr are listed for service in Spain. 8x 3-pdr were also in service at the siege.
On 14th October 1809 Napoleon ordered the formation of another siege train for Spain, consisting of 30x 24-pdr, 30x 12-pdr, 15x howitzers, 4x 324mm mortars, 8x 220mm mortars and 8x 160mm mortars. Each 24-pdr had 12 vehicles assigned to it, one to carry the gun tube, the carriage, 8x ball wagons carrying 80balls and 2x powder wagons. The 12-pdr had half this number, showing the gun tube was carried on the carriage. The 24-pdr was evidentially the long 24-pdr, its weight necessitating its transportation off the carriage, thus showing the AnXI carriage was not in use. (Clarke 15th October 1809)
hope this helps