Just to encourage people to think about building the GPF model....
The original manual is on line for this gun at:
Règlement de manoeuvre de l'artillerie. Titre Vh, Description et entretien du matériel et des munitions de 155 G. P. F. / Ministère de la guerre | Gallica
It has many drawings of the equipment and what the projectiles looked like
for diorama makers. I have a set of the drawings which have been processed to get rid of the brown "foxing" of the old paper and enhanced somewhat - just drop me a PM if you want a set.
Regards,
Charlie