Gday Nick
Don't know much about artillery emplacements, but have to agree with Al re the placement of the gun vs. trailer... Unless you depict access, it is hard for someone to view this 'snapshot' in time without wondering how this happened...
The figures look the part though, and I assume there is to be snow laid around...?
As for that jacket, it really would look the part hanging off one of the trailers... I'd get rid of the heavy MG with the ammo belt; just doesn't look right... Also the equipment should be a little more formally organised; if there is to be snow, then they do not want to be laying in it!
Have you thought maybe to raise the gun pit to the same level, and just have a sandbagged emplacement?
These are all just suggestions, so take them as just that
Let us know your actions!
Cheers
Brad