I do like armoured trains. I have for many years.
These days there are numerous kits available for both armoured trains and railroad guns.
There many available in G scale or G gauge. They come from the static model companies. like Trumpeter.
However, not only are they non-running but they are 1/35 scale, which is a bit smaller than 1/32 or #1 scale..In any event you will have to figure out how to make or modify trucks so it will run on G gauge tracks
Combat Models (combatmodels.us/) has the U.S. Naval 14" railroad gun that were used in W.W.1 to good effect. It is a vacuform model in 1/32 scale. It is not listed but he has the parts and can whip up a kit for you upon request.
I buy most of my military RR kits in 1/35 off of eBay. Search for Armored trains, railroad guns,
You will find a number in HO gauge and more in roughly OO gauge. Since I limit my RR modeling to a minimum of 1/35 scale and go up from there these smaller trains do not interest me; but some of you may like them.
On the other hand, There are kits in 1/25 scale. But these are paper card models. This is really a form of scratch building for if you want a more permanent model you can use these kits simply as patterns. You can then cut the parts out of wood, metal or plastic sheet. But they are very accurate.
An excellent dealer in paper card models is http://papermodelstore.com
Books, there are a number of good books on railroad guns and armored trains. Search on eBay under those headings,and a number will appear for sale.
Remember the movie, Dr. Zhivago? There were scenes in a Russian Armored train it the movie. Aside from the good music and the train, the rest of the movie was kind of mushy, The good doctor sleeping with his girl friend who looked like she was eternally sucking on a rancid pickle. I like his faithful wife better.
The fun thing about armored trains is that one can really invent his own armored train. Many were created ad hoc in railyards byrailroad mechanics. It is a fascinating history.
Had the same issue with my 4014. When picking up the engine the screw holding the steam pipe fell out. I tightened both. But right after I did that and put the engine back on the track, one of the screws that hold the side rods on the second driver started working loose, jammed and sheared off the hex head. I was able to back out the screw shank that was left in the hole and called MTH.
They sent me a few screws but they didn't fit. The shank was a smaller diameter and when I checked, it fit my older MTH BB. Must be they changed the fastener to a larger diameter. When I called Midge at MTH, she told me they didn't have any for the 4014s and would need to contact the supplier in China. Not happy.
I did have some hex machine screws that I used to rebuild a Bachmann 2-6-6-2 Mallet. Wham, it fit. The hex was a little larger so I was afraid it would interfere with the side rods when in motion. So I switched screws with the rear wheel since that one would have any interference. Problem solved.
I also loc tited all those side rod screws so they won't work loose again.
another look at it. I'm undecided if I like how big they are and can live with them? They should have been mounted rotated 90 degrees to make them thinner. They were already wired so it was much simpler as is.