Nothing replicates IRON NEST exactly, which is the honest starting point. What follows is sorted by which part of it each game reproduces, because "similar" means something different depending on why you liked it.
PVKK: Planetenverteidigungskanonenkommandant
The closest thing to IRON NEST's core fantasy. PVKK puts you in command of a manually operated planetary defence cannon, and it is the only game on this list that reproduces the specific experience of working a large gun by hand from inside it.
If your search that led here was for the manual bunker-cannon feeling rather than for artillery in general, start here. This is also the answer to why iron nest pvkk shows up as a search term at all — players who found one went looking for the other.
Gunner, HEAT, PC!
The right choice if what you wanted was realistic armoured gunnery rather than the paperwork around it. It simulates tank gunnery with genuine fidelity, and it is far more immediate than IRON NEST — you can see what you are shooting at.
That difference is the point. IRON NEST's tension comes from firing blind at a coordinate you derived; Gunner, HEAT, PC! puts the target in your sight. Both are gunnery simulators; only one is also a clerical one.
HighFleet
The recommendation for the dieselpunk war-machine aspect specifically. HighFleet drops the first-person simulation entirely and expands the idea into a strategy campaign, where you command a task force of enormous flying warships across the Kingdom of Gerat.
Ships, crews, fuel, resources, exploration, diplomacy and fleet composition all demand attention across the campaign. Few games match IRON NEST's combination of colossal military hardware and grimy dieselpunk machinery as well as this one does, even though almost nothing about the moment-to-moment play is alike.
Tin Can and Nauticrawl
Both are excellent if your favourite part of IRON NEST was figuring out a complicated machine from the inside, with no manual and no tutorial holding your hand.
That is the purest version of what IRON NEST is doing. Strip away the artillery, the campaign and the alternate history, and what remains is a sealed machine you must learn to operate under pressure — which is exactly what these two are about.
Beach Invasion 1945 – Pacific
The option if you want the fixed-gun defence fantasy without the engineering. It strips out most of the calculation and gives you a much more immediate version of holding a position with a heavy weapon.
Include it here honestly: it is the least similar game on the list in terms of depth, and the most similar in terms of the basic situation. If IRON NEST's arithmetic was the part you disliked, this is where to look.
What none of these give you
No game on this list combines all of IRON NEST's parts — the blind firing, the paper map triangulation, the requisition economy, the counter-battery duel, the newspaper consequences and the campaign narrative in one package.
That is worth stating rather than pretending otherwise. If you finished IRON NEST and want more of exactly that, the closest available answer is the game's own free demo with its procedurally generated objectives, and after that, the developers' stated intention to build a second, multiplayer-focused title.
Sources and caveats
The pairings above come from Steam's own "more like this" recommendations, IGDB's similar-games data, and community discussion — that is, from what players who own IRON NEST actually also play.
Availability, pricing and platform coverage for every game listed are unconfirmed on this site. So is any judgement about current quality — this page describes what each game does, not how well it is running today. Check the store pages before buying anything on the strength of a similarity comparison.