Barry,
Welcome to Armorama and in particular the Braille Scale Forum.
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For a first attempt in decades you've done a splendid job on this massive "pop-gun."
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From what I've seen, these railway gun kits are quite involved to build, let alone paint. Personally, I feel weathering is often done too excessively and for a first try you should keep it light and it appears in some of the pictures that you have. From what I've read these guns had quite a support crew so they were well maintained.
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Thanks for sharing your work and hope to see more in the future.
Cheers,
Jan