I don't know if there are any differences, Lang. I can't explain why they go onto 25pdr wheels but not CMP wheels, if they are the same. There must be small but significant variation somewhere?!?! The gun wheels did have some rust scale that I knocked away before having them sandblasted. I wonder if that worked in my favour. Whatever the case, I'm happy.
Of course, when I say they 'don't' go on CMP rims, I really mean that
tyre fitters can't do the job. My friend, the seller, can get them on. In fact, when I get back home again at the end of the week, I'll be taking my remaining wheels to him (5hr round trip) and he will fit the tyres to them all, while I wait!
From the photo of tyre on CMP wheel previously posted, you can see the equipment he used for the task. I will watch him fit the remaining tyres, ask questions, and most importantly....take photos. If I understand correctly, all you need is tyre fitting grease, some threaded rod and nuts, and a compressor. It sounds pretty straight forward actually. The tyres are definately 9.0 x 16", and they were the replacement batch for the ones that supplier sent of incorrect size (7.5 x 16").
I'll be buying enough tyres to put a set on the grey (for now) CMP, a couple for spares, and another full set for a future project.