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So I got curious about how the Gun Turret and Laser Turret really compare since the former is Physical damage and thus often faces damage mitigation from the target, whereas the latter is Laser damage and faces no mitigation. So without further adieu let's math this out:

Base Stats:

Gun Turret (w/ Piercing Magazine):
Damage: 5 Physical
Damage bonus: 100%
Fire Rate: 10/s
Base DPS: 100
Range: 17
Health: 400

Laser Turet:
Damage: 20 Laser
Fire Rate: 3/s
Base DPS: 60
Range: 25
Health: 1000

With no upgrades, the Laser Turret has only 60% raw dps of the Gun Turret w/ Piercing Magazines, but has just under 50% more range, and 150% more health. The range difference is significant when using turrets for turret-creep strategies as, the Gun Turret's don't outrange Worms, whereas the Laser Turrets do. The turrets have separate research lines, and the Gun Turret's damage upgrades stack multiplicatively with Bullet Damage upgrades.

Upgrades:
Gun Turret:
Gun Turret Damage: First 3 levels require only red and green science, and give a total of +40%, level 4 requires blue science and brings total to +60%, the remaining two levels require purple science and bring the total to +120%.
Bullet Damage: The first level only requires red science, and brings the total to +10%. Levels 2 and 3 require red and green science, and give cumulative total of +40%, level 4 requires blue science and brings total to +60%, the remaining two levels require purple science and bring the total to +120%
Bullet Shooting Speed: First two levels require only red science and give a total of +40%. Level 3 requires red and green science, and brings the total to 70%. Level 4 science also takes blue science, and brings the total to +100%. The final two levels need purple science, and bring the total to +160%.

Laser Turret:
Laser Turret Damage: First 3 levels require only red and green science, and give a total of +40%, level 4 requires blue science and brings total to +60%, the remaining two levels require purple science and bring the total to +120%.
Laser Turret Shooting Speed: The first level only requires red science, and brings the total to +20%. Levels 2 and 3 require red and green science, and give cumulative total of +70%, level 4 requires blue science and brings total to +100%, the remaining two levels require purple science and bring the total to +160%

Endgame Maximum stats:
Gun Turret:
Damage: 48.4 Physical
Fire Rate: 26/s
Raw DPS: 1258.4

Laser Turret:
Damage: 44 Laser
Fire Rate: 7.8/s
Raw DPS: 343.2

The Gun Turret has roughly 3.5 times the raw DPS of the Laser turret, however, because many enemies have physical resistance, the actual gap is smaller.

Gun Turret Actual DPS:
Vs Small Biters, all Spitters, and Small Worms: 1258.4
Vs Spawners: 1206.4
Vs Medium Biters, and Medium Worms: 1154.4
Vs Big Biters, and Big Worms: 1050.4
Vs Behemoth Biters: 798.72 (note: formula on wiki is wrong, it applies flat before % instead of the proper order, % before flat)

even against the most resistant enemies, Behemoth Biters, the fully upgraded Gun Turret still has over twice the DPS of a fully upgraded Laser Turret. However, without the full set of damage upgrades, this margin can narrow considerably, and in some cases the Laser Turret will actually out DPS the Gun Turret (especially true early on, when you first research Laser Turrets, and before having researched enough damage upgrades; also, Regular Magazines instead of Piercing Magazines dramatically lowers Gun Turret DPS, and it's possible to have Laser Turrets before Piercing Ammo is available)

These are some interesting numbers. I always knew turret DPS was higher but not that much higher.

I think its also useful to compare cost per damage, Assuming coal power. I know this differs with upgrades but lets compare both when fully upgraded. The gun turret does 48.4 damage per shot with 10 per magazine, that costs 5 copper and 1 steel.

3.5 secs per plate to smelt. Smelting speed of 2 per 180Kw Steel furnace. This gives 315Kj per plate. With 5 copper plates, 5 steel plates and one steel beam this gives total energy consumption of 4.725MJ For smelting costs.

Assuming blue assemblers are used we have to add 3 (build time of mag) / 0. 75( assembler build speed) = 4 seconds.
4 seconds *150Kw E consumption *2 (50% boiler efficiency ratio) = 1.2MJ
Mining costs = (10 ore / 0.525 ore per sec) * 90Kw * 2 (50% boiler efficiency ratio) = 3.428MJ

The energy cost per mag is therefore 9.353MJ of coal. This does not include inserter costs.

Cost per damage is therefore 9.353MJ/10/48.4 = 19.3KJ of coal, and 0.0108 of each copper and iron ore.

The laser uses 6.4MW of power and shots at 7.8 shots per second. This gives 0.79Mw per shot, and we have to times it by 2 for the 50% boiler efficiency.

Each shot does 44 damage. This gives a total of 35.9KJ of coal energy per damage point

So the laser costs twice the energy per shot of the gun, and does not cost any copper or iron. The ammo is a very energy dense material however. The problem with the lasers and steam power is always going to be having enough engines to run the thing.

Frightning wrote:in some cases the Laser Turret will actually out DPS the Gun Turret (especially true early on, when you first research Laser Turrets, and before having researched enough damage upgrades; also, Regular Magazines instead of Piercing Magazines dramatically lowers Gun Turret DPS, and it's possible to have Laser Turrets before Piercing Ammo is available)

This isn't quite fair to gun turrets because of overkill. The base damage of the laser turret is higher than the hit points of a small biter or small spitter, so in the early game it loses a percentage of its dps to overkill. Early on, the laser turret damage upgrades are nearly worthless because they don't increase actual damage, only overkill. The effectiveness comparison is not so bad with no upgrades at all because without upgrades it takes several shots from a gun turret to kill a small biter or spitter. But you can upgrade gun turrets to 1-shot small spitters or even small biters with regular ammo, at which point they are dramatically better than laser turrets which cannot have their damage meaningfully upgraded at that stage of the game. Actually AP ammo also tends to suffer badly from overkill early on, an unupgraded gun turret firing AP ammo can one-shot small spitters. With 4 damage upgrades it can one-shot small biters. After that damage upgrades aren't useful until medium biters evolve - so ironically I find AP ammo must useful when planning to not get damage upgrades at all.

Upgrades are frigging amazing for regular ammo, but there's a nuance to the damage upgrades: It's only at certain damage breakpoints that damage upgrades actually result in kill rate increases. With regular ammo, at the 3rd damage upgrade the damage goes from 4/bullet to 5/bullet, at this point it can 2-shot small spitters and 3-shot small biters, but the first two damage upgrades are nearly completely worthless, only enabling the 3rd upgrade to be awesome. The next breakpoint is 7.5 damage at which point it can 2-shot small biters, then 10 damage to 1-shot small spitters and finally 15 damage to 1-shot small biters. It actually happens these breakpoints are located fairly conveniently, if you research all the bullet and turret damage upgrades until hitting the next tier (i.e. blue science, or purple science) you tend to hit a useful breakpoint.

I call the 10 damage breakpoint "Silence of the biters" because small spitters get 1-shotted the instant they step into turret range and since the turrets fire at least 16 bullet's it's hard for spitters to walk up to the turret faster than they get gunned down (because they block each other). The *bawoop bawoop bawoop* alert only really plays when a turret runs out of ammo or if the spitters have found an unprotected target. It is comparatively much more difficult to achieve "silence of the biters" when using laser turrets because of the low fire rate and slow laser bolts.

I'm a big advocate of upgraded turrets firing regular ammo because it's so much cheaper than AP ammo, and so much more lethal against small targets than laser turrets. The upgrades are very expensive (so you need a lot of turrets for it to really be justifiable - i.e. deathworld) but you can focus on the bullet upgrades first, which also give you frigging awesome defender capsules and makes the vehicle machine gun passably useful (much better than the tank cannon, at least). The maximum damage of 19.4/bullet easily overcomes the physical resistance of medium biters and the fun only really ends with Behemoth Biters, not because regular ammo can't kill them - it can easily and it's still cheaper than AP ammo, but just because the behemoth spitters tend to cause serious problems while the turrets are tied up chewing through the biters and the short range of gun turrets become a serious limitation when they can't insta-kill incoming enemies.

Blake, dude... (this is now coming from somebody who turns OFF biters):



Really quite staggering how much thought you put into shooting biters, and taking the time to lay it out here :).

because of the significant Range advantage, what this really means if you ask me is that if you have a wall of turrets behind a wall for example, having some Gun Turrets in there will help Kill the Enemies that get close faster.


but that Range is still a significant benefit, as you can apply Damage further out, meaning effective Damage Output before you start taking Damage (well your buildings but w/e) is higher.

i think that part is important too. Killing the Enemies before they get to your Walls is more convenient than after.

This really puts lasers into a sobering perspective. Unlocking their production isn't too far behind a full LogiBot network - at which point the additional logistics of keeping turret batteries stocked with ammo becomes trivial.

Sure the 50% boost to range is helpful, but given the current pacing of upgrades, I can't imagine a defensive situation where lasers would take priority over gun turrets. It seems like laser would be relegated to defensive support and long range turret creep strategies.

Which is kind of counter-intuitive given how much work it takes to support lasers vs gun turrets. I wonder if this is intended.

Lasers are easier once you get past that initial research and build a production line though.

When building an outpost or expanding it is far easier to set down a line of laser turrets than set up a belt/bots to distribute ammo. And once you have a solar production line and drop down a few hundred panels somewhere, energy is easier than getting copper and iron for ammo production.

Then there is that 50% range bonus, and you not needing space for belts/inserters, so you can dump down a multi-layer line of laser turrets with them still being in range of the biters. Plus biters tend to attack a single point on the wall, not spreading out much, so with lasers turrets you also have more in-range turrets around the sides.


And yet another benefit for lasers is generally your more likely to run out of ammo (e.g. not enough belt capacity, or too slow feeding it, or the central chest for the logi bots ran out, etc.), or because you had a power cut so those inserters stopped, then once a biter kills one belt piece the entire line of turrets stop, than for lasers to stop entirely.

Huh, now that's interesting. I first looked at the two and figured that laser turrets were strictly superior. Maybe I will use a gun turret only defense at some point, given that they are more than competitive against laser turrets.

Still a royal pain to keep supplied though compared to the ease of laser turrets, and you'd still want some lasers around for turret creep strategies. But nice to know.

once you hit spitters, the gun turrets are useless as they out range the gun turrets which means the spitters will take out the walls and gun turrets while the biters die, and then march through no problem

The spitter will still die to the gun turrets more than fast enough, however they'll do some damage (to the turrets and/or walls) before they die. The damage can be repaired with robots, and everything that was destroyed can be replaced automatically as well.

People have build very, very large bases and defended them only with gun turrets.

In my experience laser turrets are more prone to taking damage from spitters. Especially in the early-mid game and when using the same investment of gun turrets vs laser turrets, the gun turrets will do a much better job of obliterating incoming spitters before they can spit. This is especially true in the small spitter era because small spitters have very low hitpoints making them easy for anything (including regular ammo) to one-shot them, but they spawn in very large numbers making a high fire rate desirable. The laser turret's high damage and low fire rate is a perfect mismatch for small spitters, you need like two or three times as many laser turrets as you "should" need to shoot them all before they can spit due to all the damage lost to overkill.
The larger spitters have much more hitpoints which makes the overkill problem go away, also they spawn in much lower numbers. Gun turrets are always excellent against spitters, but the laser turret is particularly poor against small spitters.

In the end game this is reversed because gun turrets become so frigging expensive to feed with ammo as a large chunk of the damage is simply wasted due to physical resistance of biters, the gun turrets are still really good against the unarmored spitters, but since they have to chew through the biters before they target the spitters this doesn't do you much good. By this point it's better to use a double row of laser turrets to just melt everything.

It's interesting to note that even with the short range, gun turrets just pour out the damage. We recently built a section of wall: 2 thick wall, solid row lasers, solid row gun turrets. After the first couple attacks, I went to have a look, see how things are going. The gun turrets, even behind the laser turrets making the range issue worse, show that they did more damage. Damage dealt was noticeably higher. I expect this would not be the case without behemoths though. The large/medium/smalls would be dead before getting into gun turret range.

One thing I'm curious about is how DPS is affected between regular and laser turrets because of how close to each other you can place them.

With laser turrets, you can have two rows where all the turrets are crammed right next to each other and have a row of medium power poles right behind them. With regular turrets, however, you'll need extra space for chests, inserters, and power poles if you want to automate reloading. I imagine that since you can place more laser turrets closer to each other, more would be in range to shoot at a huge swarm of behemoths than there would be for regular turrets.

You can direct feed ammo from one turret to the other. This allows a double row with a row of inserters in between. You can also use long-handed inserters placed betwen gaps in a second row of turrets. But in either case the second row of turrets can't hit spitters due to short range, they can help knock down the biters faster but that's all.

Good discussion! Incoming rambling wall of text below!

It's worth keeping in mind that even a laser defense battery is going to want to have bot support for occasional repairs. So lasers & guns will both want bot support at the endgame. The additional logistics of keeping guns stocked with ammo is trivial with bots - either connect to your main factory's Logi Network or for remote outposts, setup a train re-supply and have an isolated robo network at the outpost handle things that are set to resupply by train (this is easy to do by setting filters for all slots in a cargo wagon - plus you'd want this anyway for repair packs).

The build density is an interesting point. Between that and the range benefit, it creates an interesting question, it may be enough for lasers to catch up in endgame densely built batteries.

Another question that i think would be pertinent to the discussion is whether a second row of gun turrets would be able to reach over the first row to hit spitters. Gun turrets have a range of 17, and so the range of a second row would be a maximum of 15 from the first row - which is exactly the range of spitters, per my forum searches.

This would mean a 2nd line of gun turrets would need to hump the 1st line (touching), in order to be effective against spitters. To create this setup, would require a single turret gap in the center of the second row in order long insert ammo into the center turret of the front row. Which means we're feeding ammo from the center out, which also places a 1 tile columnar gap between each turret (each gun turret will effectively require a 3x2 tile area, after accounting for the turret fed directly from the chest). The resulting dps density falls to 50% in endgame designs where large defense batteries are built.

Another point to consider regarding range is how each type of turret fares when considering multiple possible attack vectors. As a best case example, with a range of 17 for gun turrets, this means that a maximum of 6 turrets in either direction (total of 12) perpendicular to an attacker at 0 range can engage an enemy. Different attack vectors, angles, and ranges will have an effect on this - some trigonometry and simulations would give a more definitive answer, but as lasers have a greater overall range, a zero range comparison can tell us a lot - comparably, at zero range, double the number of lasers can engage a target.

For oblique attack vectors including spitters, more laser turrets at the edge would be able to engage the enemy. A worst case example is a group of spitters attacking from a vector parallel to a line of turrets (a common early & mid game design where multiple rows aren't used). In this example, only the 2 gun turrets at one end of the line would engage. Up to 5 laser turrets would be able to engage. I consider this a wash mid game, due to the dps difference between the two. For larger batteries with multiple rows of turrets, dealing with oblique attacks like this favors lasers as gun turrets are not viable against spitters in any direction or attack vector beyond a depth of 2 turrets.

To recap where we are right now:
1 - Gun turrets have ~2x the dps of laser turrets against endgame biters & spitters, scaling down from ~3.5x in the early game.
2 - Gun Turret damage is dealt quickly in smaller chunks than lasers, which reduces the amount of overall dps wasted on overkill.
3 - Laser turrets have a range of 25, while Gun Turrets have a range of 17 - that's ~50% more range to lasers.
4- Gun Turrets deeper than 2 rows cannot hit spitters.
5 - Logistical support of Gun Turrets is a negligible increase over Lasers. The true impact of feeding ammo to Gun Turrets lies in the build density.
6 - Gun Turret build density falls to 50% of the potential Laser density in large endgame designs.
7 - Lasers are able to have more turrets engaged on a target when being attacked from an off-center angle.

So double the dps for turrets in the endgame, but half the build density - a wash. The true tradeoff to consider is the 2 turret depth limitation for targeting spitters that Gun Turrets have vs the amount of overkill dps that lasers waste.

TL; DR = I feel that best practice may be to use Gun Turrets as the outer row, with lasers backing them up. That will cut back on wasted overkill dps while still taking advantage of laser's greater density and range.

I don't know how much it contributes but I use Gun Turrets for the first line and Laser Turrets for the second line, which is 2 tiles behind the first due to space required for the feeding mechanism. So the Laser Turret range gets shortened by 4 tiles in total which puts the effective range of both turret types much closer together (GT 17 vs LT 21).

The laser turrets still do the most job due to still greater range even if they are in the second row. Gun Turrets occasionally help out with everything that doesn't die first hand by the Laser Turrets. Don't know how efficient it is broken down to pure math since biters rarely get to gnaw on the walls, but what I know is it saves a lot of ammo and resources than pure gun turret based defense, but preserves the high DPS of Gun Turrets when needed. I think it is the best of both worlds.

It's too bad the game doesn't support target priorities for turret types as it would help specializing a particular turret against a particular enemy and allow for more testing.

I am also quite curious how the Flame Thrower Turrets will contribute already, because they will probably change certain aspects too.



On a side note I actually found 90° corners in the perimeter to be the biggest problem of all defense related problems, no matter the turret type, but especially ugly with Laser Turrets, since the large range of the single laser turret at the corner attracts spitters/biters and gets destroyed by the spitters almost immediately due to lack of support of other turrets and from there on it causes a domino effect where spitters/biters destroy large parts of the defense around the corner due to one turret being killed after another.

That's why I never build square/rectangular defense perimeters anymore. I always use Octagons, Dodecagons (12-gons) or even Hexadecagons (16-gons) as perimeter shape with terraced turrets, depending on how large the area is I want to defend. The chance that biters/spitters will come at an almost orthogonal angle towards the perimeter increases, which means more turrets will engage the swarm, killing it faster.

This helped to minimize hotspots where Spitters cause a lot of corner damage. Avoid acute/90° angles for corners as much as possible - The more the perimeter resembles an actual circle the better.

I guess it's just basic military strategy from past centuries.

Last year I even tried using star forts (https://en.wikipedia.org/wiki/Star_fort) with bastions (https://en.wikipedia.org/wiki/Bastion) similar to the ones that have been used in 17th century fortifications but the biters/spitters are not falling for the trick of being flanked. They would attack the outer corner of the bastions every time because it is the closer target, resulting in the acute/90° angle dilemma. If they would go for the inner corners where the wall is the thinnest they would be doomed due to coming under crossfire of the two flanking bastions, too bad that they are not that dumb. Though the biters preferably attack the bastions they will never break through because bastions take forever to destroy which in return causes a lot of repair costs, which are not worth the effort. But in many other similar defense related games this strategy works wonders because most AI is programmed to seek the shortest route through the defense, which is the inner corner, not realizing that approaching the inner corner is actually suicide.

So since flanking with star fortresses is not possible with biters/spitters in factorio my most important advice is... (close to) circle shaped perimeters.

Interesting stuff, I feel that one key point is being forgotten though: Laser Turrets have 250% of the hitpoints that Gun Turrets have, which means they are far less likely to die from spitter damage when attacked. Gun Turrets will also typically die with about 10 mags in them, which assuming Piercing Magazines means 50 Copper Plates and 10 Steel Plates more in materials you have to replace. I actually think the best idea is to put the laser turrets in front so they can tank spitter damage for the gun turrets (since Laser Turrets need no additional space, the gun turrets can still attack the spitters exactly when they are in attack range relative to the Laser Turrets). What the Gun Turrets really help with is killing the Biters faster, even with their Physical armor, Gun Turrets still handedly out-DPS laser Turrets.

MeduSalem wrote:I don't know how much it contributes but I use Gun Turrets for the first line and Laser Turrets for the second line, which is 2 tiles behind the first due to space required for the feeding mechanism. So the Laser Turret range gets shortened by 4 tiles in total which puts the effective range of both turret types much closer together (GT 17 vs LT 21).

The laser turrets still do the most job due to still greater range even if they are in the second row. Gun Turrets occasionally help out with everything that doesn't die first hand by the Laser Turrets. Don't know how efficient it is broken down to pure math since biters rarely get to gnaw on the walls, but what I know is it saves a lot of ammo and resources than pure gun turret based defense, but preserves the high DPS of Gun Turrets when needed. I think it is the best of both worlds.

It's too bad the game doesn't support target priorities for turret types as it would help specializing a particular turret against a particular enemy and allow for more testing.

I am also quite curious how the Flame Thrower Turrets will contribute already, because they will probably change certain aspects too.



On a side note I actually found 90° corners in the perimeter to be the biggest problem of all defense related problems, no matter the turret type, but especially ugly with Laser Turrets, since the large range of the single laser turret at the corner attracts spitters/biters and gets destroyed by the spitters almost immediately due to lack of support of other turrets and from there on it causes a domino effect where spitters/biters destroy large parts of the defense around the corner due to one turret being killed after another.

That's why I never build square/rectangular defense perimeters anymore. I always use Octagons, Dodecagons (12-gons) or even Hexadecagons (16-gons) as perimeter shape with terraced turrets, depending on how large the area is I want to defend. The chance that biters/spitters will come at an almost orthogonal angle towards the perimeter increases, which means more turrets will engage the swarm, killing it faster.

This helped to minimize hotspots where Spitters cause a lot of corner damage. Avoid acute/90° angles for corners as much as possible - The more the perimeter resembles an actual circle the better.

I guess it's just basic military strategy from past centuries.

Last year I even tried using star forts (https://en.wikipedia.org/wiki/Star_fort) with bastions (https://en.wikipedia.org/wiki/Bastion) similar to the ones that have been used in 17th century fortifications but the biters/spitters are not falling for the trick of being flanked. They would attack the outer corner of the bastions every time because it is the closer target, resulting in the acute/90° angle dilemma. If they would go for the inner corners where the wall is the thinnest they would be doomed due to coming under crossfire of the two flanking bastions, too bad that they are not that dumb. Though the biters preferably attack the bastions they will never break through because bastions take forever to destroy which in return causes a lot of repair costs, which are not worth the effort. But in many other similar defense related games this strategy works wonders because most AI is programmed to seek the shortest route through the defense, which is the inner corner, not realizing that approaching the inner corner is actually suicide.

So since flanking with star fortresses is not possible with biters/spitters in factorio my most important advice is... (close to) circle shaped perimeters.

I've never tried myself, but I was under the impression that biters will attempt to path 'around' walls. Only if they don't find an open path within x tiles, will they attack the walls. So with your star fort, did you try leaving a gap at the inner corner?

starholme wrote:I've never tried myself, but I was under the impression that biters will attempt to path 'around' walls. Only if they don't find an open path within x tiles, will they attack the walls. So with your star fort, did you try leaving a gap at the inner corner?

Yeah, I tried that once... Problem are the Behemoths in later stages. If some of them keep the turrets engaged for too long then some Biters might slip through the gap during heavy attacks and cause a lot of chaos within the base.

On light/medium Biter settings it may work though... There they probably all die before reaching the gap. Can't tell since I never tried there. But under hard mode I basically had to reload the savegame from a safe spot because it got a little bit... out of hand... since I am not really having the environment friendliest base behind the perimeter to say it mildly. So the perimeter is under attack constantly, eventually something slips through if there are gaps.

Flanking would be nice to increase the amount of turrets pointing at the same area, but even if the biters are suicidal enough to go for the deathzone in inner corners it wouldn't prevent some scratches on the walls here and there if 2-3 super-nests decide to send their hordes at the same time. There are just too many of them and once Behemoths start appearing they are way too tough to kill before at least some of them reach a wall/gap.



Also there would have to go more research into how much detour the biters are willing to take to reach the gap within the deathzone and with that determining the overall distance between inner corners, because if they are spaced too far apart,then they will engage the outer corners no matter what, which also happened with my attempt because my base was quite far stretched.



There are two other things I never tried in any game yet: Mine fields or Express Belts.

It might be worth giving another try if someone mines the gaps or uses excessive Express Belts to slow them down before the gap. I might have a look into it when 0.13 is out because I am probably going to play the game from scratch then anyways with fresh and new ideas.



Something that I did see some people do in other threads is having something like Ravelins (https://en.wikipedia.org/wiki/Ravelin) in near distance of the wall, which are basically small fortifications detached from the main fortress. I tried something like that as well but I didn't have much success with that either because if the turrets of the Ravelin engage the biters before they are in the deathzone between Ravelin and main fortification where the horde is surrounded by turrets from all sides then they might decide to switch target and go for the small fortification. Becomes costly if the hordes tear down these Ravelins half the time because they can't fend off an entire horde on their own. So I don't know how people get the biters to ignore these little outposts before they enter the deathzone.

But that is something I want to try out with 0.13 again when there is something like sensors to spot the enemies. Then I would cut off power to the turrets as long as the biters aren't in the death zone so Biters ignore them and once they are lured inside, bring up all fire power from all sides. Pretty much like a trap.



So there are hypothetical improvements to the star fort, but they are all cost and time intensive to build compared to a much simpler octagonal shaped perimeter which does the job too at the cost of a little bit more wall damage.

I think that with the Circuit Network Changes in 0.13 it should be possible to keep the turrets in a Ravelin from shooting as long as none of the turrets in the "main base" is actually shooting as well. However, this might not work if the attacking wave is really stretched out.