Did you have a particular reference to build your train off of or just went for general look? I want to do one that I can use for WW1 Eastern front and RCW and generic enough to use for either side.
Short answer
The train concept was to create something useful for gaming that looked the part but wasn't ever intended to be a straight copy.
Long waffly answer
My reasoning is that I wanted to represent one real train on the game table, not a group of 2-4 real trains. So my model train had to be scaled down in the same way we make a few scale houses represent a village. A realistic scale representation of a period armoured train would leave us with something too big and too heavily armed on the game table. A typical light armoured train of the period, the kind intended to go up to the front, might consist in reality of an engine, fuel tender, two gun carriages and some flatbed trucks at the front and back. They might then have additional truck or two for carrying an infantry company, some cavalry scouts or perhaps an armoured car. The armament for the historical train might be 4 76mm guns and 12 MGs. If a group of 10-20 figures represents a battalion of around 200-400 men at a typical game scale of 1:20 then a gun model is probably representing ~2 artillery pieces and a machinegun base ~4 guns. So our historical train should have in game scale 2 model guns and 3 model MGs worth of firepower but our historical model converted to game stats would be 4 model guns and 12 model MGs, i.e. the equalivalent of a unit of 2-4 real trains.
So, given I couldn't build a straight copy I looked for a 'smaller' historical train to use as inspiration.
I found this one, the Red Siberia, that was used in the theatre I was modelling and had just one gun tower per carriage.

My train carriages are also shorter and based on two wheel trucks instead of four wheel long passenger coaches. The windows are also closed, so the model train MGs can fire from any window. The additional troop carriage is to represnt a few trucks that could carry enough men to be an infantry unit in game terms and dismebark from the train. I can add it or not as the scenario requires. These compromises and cheats give me a train, which while still too big, is far less excessive for the game scale and can be reasonably armed in game terms while retaining a nice WYSIWYG feel.
If you want to make a WW1/RCW generic train then you could get one of these sets from evilBay and convert it into something 'inspired' by train 5 from Curprum's link.

You can forget about the flat bed trucks. In a game I'd give the train a chance to not be derailed by mines or track damage to represent them being there. I'd also drop the front armed carriage to reduce the length and firepower of the train. Then you'll need to convert the open truck into the front gun carriage by stripping it back to the flatbed and adding a plasticard turret. After that convert the carriage or guard's van into the rear armed carriage on train 5. Note the actual carriage you get in the set seems to vary randomly. The one shown in the lower part of the picture and one on the box are different. I've got one of each in the two sets I have. Either would be fine for conversion. Actually if you don't have any track already you might want to look at the Fastlane sets as they have a truck in some that looks more like the one pictured on train 5. They usually come with more carriages and trucks too. Sadly the track and truck couplings vary between manufacturers. The trucks and engines usually join anyway but the track doesn't. If you aren't going to use the joins it probabbly doesn't matter. Last you armour the train and tender with more plasticard or cardboard. Alternatively if you want something more purpose built take train 7 and cut down the gun carriages like I did on my Red train. Either would work as a plan and give a pretty cool armoured train that could be used in games and not be OTT. In fact I might do one myself as I need a train for my Whites.

If you want more info for inspiration the trick I've found is to use Google Translate to get your search terms. This then finds Russian web sites that can then be translated.
This is the Russian/Cyrillic for armoured train.
бронепоезд
Here are some armoured train links. This is probably way more than you need but others might find them useful too. Actually, I think I'll start a separate armoured train thread to post these into and others can add more links. I've put the original Russian language links below but you can just paste the URL in here to translate.
https://translate.google.com/https://www.minecreek.info/volunteer-army/white-armored-trains.htmlhttps://reibert.info/threads/krasnye-bronepoezda-i-bronetexnika.116428/http://wio.ru/rr/ww1.htmhttp://wio.ru/rr/ww1red.htmhttp://wio.ru/rr/ww1white.htmhttps://naukatehnika.com/bronepoezda-belyix.html&usg=ALkJrhi5fzVn8FrR2FsCqV8zXbxfajLroAhttps://naukatehnika.com/v-odnom-stroyu-zaamurecz.html&usg=ALkJrhjru99fNkR8OqptPI3Rk6JKNgiGRwhttps://naukatehnika.com/na-frontax-grazhdanskoj-vojnyi-bronepoezda-krasnyix-chast-1.html&usg=ALkJrhih38N4nJ1O4QKkW-Vi4eaf6BcRyghttps://en.topwar.ru/34152-russkie-bronepoezda.htmlhttp%3A%2F%2Fsamlib.ru%2Fk%2Fkrasilxnikow_o_j%2Falabiev.shtmlhttps://coollib.com/b/301551-leonid-ilyasovich-amirhanov-bronenostsyi-zheleznyih-dorog&usg=ALkJrhhbta47cuE4iHBnQGxrmj5Ma3NRDgPS Nice stuff on your blog. I hope you make a train as I look forward to seeing the results.