Accuracy of Modern Tank Guns

[Balrog]

Inspired by another thread in the scifi forum, what is the measure of accuracy for modern tank guns? If you aim it at a target, how many degrees will the round be off when it reaches it? I know a big deal is made of stabilization while on the move, but is there a noticeable difference between sitting still and driving around whilst acquiring different targets who are also moving, etc?

[Kojiro]

I don't know how accurate the actual aiming is but this seemed on topic:

I have no actual idea how accurate they actually are though. Can't imagine they're too inaccurate though.

[Esquire]

Depends on the round; apparently, Rheinmetall claims 20cm dispersion at 1km for their APFSDS round, according to this thread. That's for the Abrams main cannon, I presume; other modern tanks ought to be at least broadly similar.

[Zixinus]

I don't know how accurate the actual aiming is but this seemed on topic:

It shows that there is a system in place in the tank to keep the barrel on-target even when going at speed on bumpy terrain. Maybe computerized.

[Sea Skimmer]

Inspired by another thread in the scifi forum, what is the measure of accuracy for modern tank guns? If you aim it at a target, how many degrees will the round be off when it reaches it?

Accurate to about .3 mils at 2km would be typical for ~1990 tech under battle conditions, not many new tank guns have been fielded since that date though the ammunition has gotten better. The NATO 140mm guns were all intended to be much more precise weapons. Past ~2km velocity drop off and the steadily higher angle of fire will reduce total system accuracy.

Some of this inaccuracy is from the gun and ammo, some if from the fire control and boresight alignment. Boresight will always get worse the more you fire, and the more worn the gun the less accurate it will be, though it may actually be slightly less accurate when brand new, needs a break in period.

I know a big deal is made of stabilization while on the move, but is there a noticeable difference between sitting still and driving around whilst acquiring different targets who are also moving, etc?

At 2km it makes little difference, for longer range precision fire being stationary will be usefully more accurate. Tank fire control systems have improved considerably since the COld War though, and been commonly upgraded unlike the guns, at this point the US Army considers the M1A1AIM variant usefully accurate to 4km firing ranges against enemy tanks and the M1A2 to about 5km. Keep in mind at these ranges the crew would expect to have to adjust fire, which can be difficult to 'sense' through the clouds of dust and smoke thrown up by the vehicles own muzzle blast. This is a major reason why tanks don't normally have muzzle breaks FYI, it would make that problem waaay worse.

NATO 140mm projects + fire control were geared towards a useful accurate range of 6-7km. Not that every or even many rounds would hit, but that a tank with a full load of ~30 rounds of ammo could destroy multiple enemy vehicles at that kind of range. Some of this would be simply because the shells had triple the muzzle energy and would be much faster (as an average speed, cause less velocity drop off) and so far less affected by wind.

For an example of what they intended the US project aimed for the error budget produced by the gun tube and chamber precision of manufacturing taken alone to be only .025 mils. No reason exists why you can't build a 120mm barrel to that precision, some of the actual new ones might be that good, its just as I said, not many actual new tank guns have been fielded since the early 90s by any major power. Generally you will only find data like this for old or abandon systems.

http://www.dtic.mil/ndia/2008gun_missile/6526Huls.pdf
Also see this document as a quickie, it has some images of actual 120mm targets hit in test conditions at 1700m range. In one case two shells went through the same hole.

[Zeropoint]

I note that the results are roughly one to two minutes of angle (using the "one inch at one hundred yards" rule of thumb) which would be considered "pretty decent" in a hunting rifle. According to Wikipedia, "A standard-issue military sniper rifle is typically capable of 1-3 MOA (0.3-1 mrad) accuracy".

Just throwing that in for a point of comparison.

[Micro-Balrog]

It's worth noting that stabilization while on the move is best to be described as "firing during short stops". It's not really possible to predict what bump you'll hit next, but stabilizers do help a lot. So it's now possible to fire during short stops where previously the rtank gun would still be affected by the inertia from movement.

[Simon_Jester]

I imagine the stabilizer can also be used if you don't want to stop, think you have a good chance of hitting with your next round, and are willing to gamble on a hit.

[Sea Skimmer]

The earlier stabilizers from WW2-1960s were kinda always bouncy, sometimes even when you were still, in a progressively more tolerable way. They only did 1 axis control too. It was useful for suppressive fire with main gun and machine guns, including against enemy tanks, more so then for effective tank killing. For kills you could gain an advantage on a hard surface road, but not much of anywhere else. From the 1970s onward we've had 2 axis minimal stabilizers. Now some tanks have 3 or 4 axis, and several tanks now actually do have the ability to predict the bounce of the tank.

This is accomplished via LIDAR or MMW radar aimed at the ground directly ahead of the vehicle, it only needs to scan 1-2 feet ahead, where detection by the enemy is highly unlikely. This isn't a crazy miltech either, you could start buying luxury SUVs with these kind of sensors years ago to get the suspension, a feature shared by aid tanks. Also many recent experiments with unmanned vehicles. Japanese Type 10 and I believe the second variant of the Korean Black Eagle actually field this as tanks. I suspect the total advantage is low, but it is another correction axis to be measured and should do something positive.

For ultimate accuracy the thing to have just becomes a radar on the tank to measure its own outgoing shell course, unfortunately the required antenna is fairly large making it more suited as a way of adjust indirect fire SP howitzers. End result is unguided artillery fire 50-75% more accurate after you first fire a couple of rounds to measure the atmosphere. Only one vehicle necessarily needs to do this, it can auto pass the correction to howitzers closely around it.

With a modern tank the stabilizer isn't perfect, but its able to render gunnery inside about 1500m a point and shoot affair. The gunner needs to set a battle sight range, but as long as that's fairly close, say 100m, the whole system is good enough that the round will hit a tank, and a specific part of the tank if the gunner is trained to a high standard. You don't need to wait for a new ballistic solution if you know what your doing even while on the move.

As the range goes past that your going to gain more and more advantage from fully exploiting the computer including multiple laser rangefinder uses to calculate the actual path of the enemy vehicle. The simple error from the stabilizer-gun sight-gun barrel alignment issue you get though isn't that big. .035 mils of your .3 total error perhaps. Many factors are ~10% kind of error sources. Which means major advances in accuracy need to reduce many errors. Simply making the gun BIGGER AND MORE EXPENSIVE is the best solution ever to this.

The whip of the gun barrel is a very important perimeter for firing even when stationary, as an example of something still making inaccuracy when stationary. Thus the muzzle reference sensors on modern tanks, which also aid fire on the move in other ways. Also You do need to manually boresight your actual optical sight pretty often, since no computer can do that for you in a reasonable fashion.

Also sabot ammo will always be more accurate then full caliber rounds out of a smoothbore at these kind of distances. Everything else is at least 300m/s slower to as much as 900m/s slower and these speeds don't equalize until ranges past which 120mm gun tanks are going to be capable of engaging each other with unguided weapons. In principle though no reason exists why you can't use a tank gun as a sniper rifle, and with the sabot round kill people behind several concrete buildings.

The maximum firing range IIRC for the US 120mm M256 is with the HEAT round and 32,000 yards; assuming you built a ramp or parked on a slope to gain the required elevation of course. You'd be shelling town centers at that kind of distance like normal artillery.

[Sea Skimmer]

Since it also came up in the other thread, typical MBT turret traverse speeds are 40+ degrees from 1970s forward, WW2 traverse speeds could be up to 30 but were typically low, 6 degrees per second for the worse case Tiger situation. But electric motors have become so awesome since the 1970s that at this point your speed is really just about how much you care. Anti aircraft systems can do 120+ degrees per second, and acceleration rates to that kind of speed that are in the 60-100 degrees per second per second kind of range.

Your biggest limit is probably using a human gunner. With radar on the tank automatic engagements would become reasonable in principle. Some ATGM platforms already use radar as the only fire control sensor.

[Esquire]

That's a significantly faster traverse rate than I would have thought - I wonder; do you happen to know standard CAS aircraft attack altitudes and/or speeds? I'm wondering if it's theoretically feasible for tanks to shoot down attacking helicopters or CAS aircraft with their main cannon. Obviously it wouldn't be ideal or even that useful a capability under operational conditions, where presumably dedicated AAA vehicles or emplacements would be available, I'm just curious.

[Simon_Jester]

Basically the problem is tracking a target; tanks don't have AA gunsights and tracking mechanisms, nor do they have the kind of proximity-fuzed shells you use when you actually want a shell fired from a gun to destroy an aircraft...

[Esquire]

Certainly; I was wondering if it were physically possible for a tank to traverse its turret fast enough to keep up with, say, a low-flying attack helicopter a kilometer out, not if it would make any sense to use tanks for antiaircraft fire - it clearly doesn't. I don't know how specialized modern sighting mechanisms are; I'd think we could at least design something with as much flexibility as a WWII dual-purpose gun if we wanted to. Not that we would, of course.

[U.P. Cinnabar]

Certainly; I was wondering if it were physically possible for a tank to traverse its turret fast enough to keep up with, say, a low-flying attack helicopter a kilometer out, not if it would make any sense to use tanks for antiaircraft fire - it clearly doesn't. I don't know how specialized modern sighting mechanisms are; I'd think we could at least design something with as much flexibility as a WWII dual-purpose gun if we wanted to. Not that we would, of course.

Which means a tank would have to have AA rounds, as well as cannister, HE, and the various anti-tank rounds. And, the tank has a limited ammo supply to begin with.

[Esquire]

Yes, I know. Unlike some posters, I'm well aware there's no plausible scenario where actually using a tank this way would make any sense, I just want to know if it's physically possible - rather, I was hoping Skimmer would know the missing CAS attack height variable off the top of his head so that I could do the calculations myself. Sorry if I didn't make that clear.

[Elheru Aran]

I want to say that there are accounts of tanks doing exactly that to helicopters, probably Israeli if anyone, or *vaguely possibly* Iraqi-Iranian tanks.

It's been a really long time since I saw the story in question so I can't quote any source, though. A quick Google suggests that it's either bad reporting confusing armoured AA vehicles with proper tanks, or tanks/IFV's using their machine guns/onboard SAM's.

[Beowulf]

Basically the problem is tracking a target; tanks don't have AA gunsights and tracking mechanisms, nor do they have the kind of proximity-fuzed shells you use when you actually want a shell fired from a gun to destroy an aircraft...

https://en.m.wikipedia.org/wiki/M830

Proximity fused shell. Designed for use against helicopters, amongst other targets. Depending on distance, could also use canister.

[Simon_Jester]

Huh. Should have double-checked what I thought I knew.

[Sea Skimmer]

Which means a tank would have to have AA rounds, as well as cannister, HE, and the various anti-tank rounds. And, the tank has a limited ammo supply to begin with.

US Army set out to solve that problem a while ago, though for lack of funding it only went into production engineering last year. XM1069 Advanced Multi-Purpose, intended to replace all M1 tank shells other then the sabot rounds. Basically they took a concrete piercing shell design, gave it a timed fuse option as well as delay, and put two caps on it. One cap is the concrete-light armor penetrating cap, on top of it is a cap that actually shatters into a hail of forward fragmentation, something normally weak in a HE shell, replacing the canister and AA roles while using the time fuse. It will still penetrate solid concrete blocks, buildings and steel as thick as the sides of tank turrets.

Laser range finder accuracy is +/- 10m by design, and can be near perfect in good optical conditions. So if you lase a helicopter and then fire you'll burst within a dangerous range, and the helicopter wouldn't have over 2 seconds of total evasion time (from we assume, detecting the laser pulse)at 2km range. Very good reason to use a system like Longbow Hellfire against tanks.

Russia had laser ranged HE rounds on some tanks in the 1980s, but the shell itself was a simple HE-frag type. The Israelis also have that one cluster shell, that can make its bomblets air burst, but it has almost no penetration capability.

Certainly; I was wondering if it were physically possible for a tank to traverse its turret fast enough to keep up with, say, a low-flying attack helicopter a kilometer out, not if it would make any sense to use tanks for antiaircraft fire - it clearly doesn't. I don't know how specialized modern sighting mechanisms are; I'd think we could at least design something with as much flexibility as a WWII dual-purpose gun if we wanted to. Not that we would, of course.

You can totally go after helicopters, helicopters have very low survival prospects if they come physically close to armored formations. But that's why they have such long range anti tank missiles on themselves, and even the unguided rockets can attack large formations from several kilometers away without hopeless accuracy.

Against fast jets the slew rates are still too low to have much chance, and jets tend to attack from high angles. But that's no given, the Euro Tornado for example was meant to attack armor by skimming over at about 200ft with a huge mass of cluster bombs or anti tank mines. Still overall speeds are high, you really need to 60-80 degree per second rates or higher to engage well. In the case of popup attacks the jets need to stay under 2,000ft or they'll never complete the whole attack before being blown out of the sky.



As for fire control, some tanks now have auto tracking in the FLIR sighting system which could certainly hit a helicopter but its doubtful that will work against a jet target. Few jets would now come to close quarters anyway these days. The modern trend is heavily towards simply risking the radar SAM threat and flying at 15,000ft. So many standoff weapons are on planes now, even JDAM can glide 15 miles best case, that its very easy to do so. Strafing retains value but for support of infantry rather then an anti tank tool.

Even by the late cold war the survival of A-10 style popup attacks was largely being based on the idea that Army helicopters and ATACAMS missiles would first destroy the more serious part of the air defenses, and ground forces were to prioritize AA system destruction over anything but Russian command tanks.

[U.P. Cinnabar]

US Army set out to solve that problem a while ago, though for lack of funding it only went into production engineering last year. XM1069 Advanced Multi-Purpose, intended to replace all M1 tank shells other then the sabot rounds. Basically they took a concrete piercing shell design, gave it a timed fuse option as well as delay, and put two caps on it. One cap is the concrete-light armor penetrating cap, on top of it is a cap that actually shatters into a hail of forward fragmentation, something normally weak in a HE shell, replacing the canister and AA roles while using the time fuse. It will still penetrate solid concrete blocks, buildings and steel as thick as the sides of tank turrets.

Laser range finder accuracy is +/- 10m by design, and can be near perfect in good optical conditions. So if you lase a helicopter and then fire you'll burst within a dangerous range, and the helicopter wouldn't have over 2 seconds of total evasion time (from we assume, detecting the laser pulse)at 2km range. Very good reason to use a system like Longbow Hellfire against tanks.

Russia had laser ranged HE rounds on some tanks in the 1980s, but the shell itself was a simple HE-frag type. The Israelis also have that one cluster shell, that can make its bomblets air burst, but it has almost no penetration capability.

I stand corrected on all counts. Thanks, Skimmer.

[Sea Skimmer]

Yeah pretty deadly inside 2-3km, of course the counter balance is that four Apaches can exposed just one helicopter with Longbow, then fire 64 independently targeted missiles in a ripple from 8km away. This is not good for tank survivability considering nothing on earth right now stands what you could call a good chance against a missile that heavy from above. The helicopter can hover behind anything for cover too, it could be the one and only building on the horizon...

The US Army in various whatever studies that are around from the late 90s, basically ended up figuring that against the best Russian air defense gear of the 90s and everything else...even the Longbow Apache force would be taking 15% losses per mission. So in a couple days you have no damn aircraft left in a battalion. But each one might have easily knocked out dozens of tanks, so its still totally worth having the Apache, but as the rules tend to go when high end systems fight each other nothing lasts long.

Comanche was supposed to improve that but it ended up too heavy to fly, the cost itself was not so unreasonable had it worked. Since then attention to improving CAS survival has largely focused on integrating UAV control into the helicopters, something now demonstrated for Apache-Grey Eagle teams with live missiles, and employing more direct links between supporting fixed wing planes and artillery.

...and replacing the A-10 with another armored strafing plane is absurdo dumb but you just cannot tell this to it's true believers.

[Sea Skimmer]

Some quick data for XM1069 from back when it was an experiment for Future Combat System.
http://www.dtic.mil/docs/citations/ADA481079

http://www.dtic.mil/ndia/2009insensitive/6Bpfau.pdf
This is a bit newer concerning IM testing of the basic design, I include it mainly because it shows the cross section well. The fuse is the base cap in the base with booster and then the main explosive above it. Stabilizing fin stick not shown.

[Simon_Jester]

...and replacing the A-10 with another armored strafing plane is absurdo dumb but you just cannot tell this to it's true believers.

The problem is that they see the low cost and ability to survive massive amounts of automatic cannon fire, and assume it translates into ability to survive missiles. Plus of course largely ignoring the air to air threat.

[Sea Skimmer]

Also the armor was against 23mm API cannon, and 37mm HEI round detonating on contact. That's pretty impressive, but most modern AA guns, even some in the west before this point already mounted much more effective guns. The Quad 30mm setup on the Tunguska is certainly a match for the A-10 at the king of ranges the GAU-8 can actually kill tanks at. Its really not that penetrating, cold war tanks sides were all proof against it, just not the tops.

A better anti tank cannon would be possible in various ways, but its never going to get back the relative effectiveness the A-10 had in 1972. Even by the mid 1980s the desire was to orient it towards a missile platform, spamming that HVP laser guided hypervelocity missile with a simple beam riding guidance system. Russia worked on a 200mm smoothbore gun firing guided HEAT shells as an utter alternative. Being scaled for use on the Su-25.

[Sea Skimmer]

So according to a unclassified army report from 2005 ~ apparently the M1A1 tank for its original 120mm gun trials was rated as capable of a 95% chance of a first round hit at 2,200m on a stationary target while moving 25mph on rough terrain. Seems reasonable to me for 1985.

Stabilizer on the M60A1 was tested for 75% hits at 1,500m at 15mph; but with a much higher chance the entire system would be plain broken and much more time required to complete the act of aiming. 10 seconds vs 2-3 seconds between targets successively engaged.