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I want to share some math about turrets and their ammo. Be aware that there are different numbers over the internet, that may be because one didn't account damage resistance, have different patch, or one of us did make a mistake. So I encourage you to do the same math and check the numbers.

DPS against each biter type at different tech level:
Base - without techs
pre SP3 - all possible techs with Science pack 1, Science pack 2, Military science pack
pre HTSP - same with Science pack 3
pre Space- same with High tech science pack

Gun turret, Firearm magazine Gun turret, Piercing rounds magazine Laser turret To calculate cost of turrets and ammo, I had used following assumptions:
1 Iron ore = 1 Raw Resource
1 Copper ore = 1 Raw Resource
1 Coal = 1 Raw Resource = 4MJ of energy
1 Crude oil = 0.1 Raw Resource
Buildings used for production - Electric mining drill, Steel furnace, Assembling machine 2
Steam energy

Costs in Raw Resources:
Gun turret = 54.87
Laser turret = 246.50
Firearm magazine = 4.39
Piercing rounds magazine = 15.6

Damage per resource:

Gun turret, Firearm magazine Gun turret, Piercing rounds magazine Laser turret It's hard to calculate Flamethrower turret stats, but I recommend to look at this post - viewtopic.php?p=311808#p311808
If all or most of its damage scale with techs, then it should be considered the most cost-effective turret before free energy.

Uranium rounds magazine deals huge damage. But the opportunity cost is quite intriguing. One U-238 using Kovarex enrichment process and Nuclear fuel reprocessing can be converted into 5263 laser shots, if add to this 4*Productivity module 3 in assembler making Uranium fuel cell and then use it in 4-reactor nuclear setup, it can be converted into 30882 laser shots.

• What I find worth notice:
• gun turrets with piercing rounds magazines keeps leading in DPS for a long time
• laser turret cost less than gun turret with 13 piercing round magazines
• to deal 1 damage to small biter with piercing rounds you need to waste more energy on production, than to do it with laser turret. In other words shooting with piercing rounds creates more strain on energy than shooting with laser

Are those numbers per shot or per second?

Overkill is pretty important factor at least before "Big" enemies. Things only die in an integer number of shots and excess damage from the killing shot is wasted. For example, laser turret always kill small biters and spitters in exactly 1 shot regardless of upgrades. Small spitters die in 2 shots to un-upgraded regular magazine. Integers largely simplify things.

Laser turret costs 0.2 coal to fire once (800kJ = 1/5th of 4MJ), it kills any small enemy for 0.2 coal since 20 damage is more than 15/10hp.
Regular ammo costs 4 resource/magazine or 0.4/bullet. Small enemies die in 3, 2 or 1 bullets depending on upgrade, or 1.2, 0.8 or 0.4 iron plates. So even in best case scenario, where most of a laser turret's damage is being wasted to overkill and the gun turret is upgraded enough to 1-shot enemies with the cheapest ammo, it's still more economical to use laser bolts than regular ammo.

Flamethrower turret is best analyzed in this way: Fire kills everything and quickly. It consumes 3 oil/second. The amount of resources to incinerate a wave is thus just 0.3 * firing time. I'd guess a flamethrower in an efficient defensive setup normally fires for 10-20s when a wave attacks and most attackers will die to that fire (unless abusing walls some will need to be shot). That works out as 3 to 6 resources to kill 10-30 attackers, or somewhere between 0.1 to 0.6 resources per attacker. The scary thing about flamethrowers is it's potentially competing with lasers and definitely out-competing guns even for incinerating small biters and spitters, yet fire kills "Big" enemies almost as fast, which will take 10+ laser bolts. So fire is good against small enemies and frigging amazing against medium/big/behemoth enemies.

There is also one final factor: Gun Turrets have substantial reserves for their ammo. In practice, a gun turret won't hold less than 10 ammo + 8 on a feed belt (2 tiles) + maybe 2 in inserter hand or 20 ammo (and if you're hand feeding, you'd probably put even more in a turret). That increases the initial investment of a gun turret by 80 resources for firearm magazine or 280 resources for piercing rounds magazine. Laser Turrets chamber exactly 1 laser bolt increasing their cost by 0.2 resources, and flamethrowers reserve 100 fuel, or +10 resources. Here again Gun Turrets are serious losers and the only thing they do well is obliterating swarms of small enemies in a fraction of a second.
(Yet another interesting analysis, is that a behemoth biter requires around 240 resources in piercing ammo to kill: enough resources to build an entire laser turret).

Illiander42 wrote:Are those numbers per shot or per second?

DPS = damage per second

Good points, BlakeMW.

I want to add that laser turrets have a drain i.e. maintenance cost - 24kW or 21.6 Raw Resource per hour if on steam energy. That isn't much even for early game, but should be considered as a drawback for places with very low biter activity.

While in theory

SilverShadow wrote: Flamethrower turret should be considered the most cost-effective turret before free energy.

it has some problems in practice:

• it is better to remove trees in front of a turret, which would lead to less pollution absorption and "can't" be done without bots
• it is less convenient to place and remove the pipes than poles and you wouldn't use these pipes for other purposes. Terrain with cliffs, water pools and border curvature makes it worse

Trees are absolutely easy to clear out with grenades.

Flame turrets give an enormous amount of damage but at the same time the resource cost is potentially very high. Turrets burn precious oil which converts into solid fuel. When burning light oil the turret consumes 3/sec, which is effectively consuming 3.75MW worth of steam energy. But it's not like you need more than 1.

bobucles wrote:When burning light oil the turret consumes 3/sec, which is effectively consuming 3.75MW worth of steam energy

That would violate one of my assumptions:
1 Crude oil = 0.1 Raw Resource
1 Coal = 1 Raw Resource = 4MJ of energy

Which is ok, but we need to be clear about that. You give [oil more value], or [energy and coal less value], which brings laser turret in a more favorable position relative to flame turret.
And that makes sense. I think if you have enough petroleum it is a good idea to convert light oil to solid fuel and use it as a cheaper energy source.

Btw to specify the value of different oil I use following reasoning. Most needed oil products are petroleum, following by light oil. Easy way to check if it's true to your base - look at cracking chemical pants, if you are cracking heavy into light and light into petroleum, then it is true. This means that we can evaluate crude, heavy and light oil by how much they contain petroleum minus energy and pollution_penalty needed for oil processing and cracking. Advanced oil processing is superior for this purpose, because it produces more petroleum.

To simplify for now, lets neglect energy and pollution:
Crude oil = 0.9 Petroleum gas
Heavy oil = 0.5 Petroleum gas
Light oil = 0.67 Petroleum gas

That means that you should use heavy oil in flamethrower turret.

Probably the best criteria for Oil and Uranium is extraction effort rather than energy value. Unfortunately, this is super hazy for Pumpjacks, but I feel that in the current version of the game 10 oil generally requires slightly less extraction effort than 1 ore, given that a pumpjack is often producing more than 15 oil/s, vs ~0.6 ore/s for Electric Mining Drill. Depends a lot on map too though.

Taking something like Uranium, it might be fair to say it takes 25x the effort to get 1 U-238 than 1 Iron Plate (2x mining time, 10 ore per U-238, +25% extra for sulfuric acid). Most likely, there is a magnitude more uranium ore available than is required to produce U-235 to make power, so the question really is putting 25 miners on uranium ore, versus some other ore or coal.