Increasing the Range of Howitzers

[anorlunda]

They are quite expensive though, so I'm not sure they'll ever entirely replace older style unguided shells.

The word entirely is perhaps too broad.

I think it is interesting to watch what happens. If it takes only 1 guided projectile to destroy the target rather than 100 or 1000 dumb ones, then it is probably cheaper, and has fewer incidental victims. The same argument applies to smart bombs, or even to cruise missiles. Expense versus accuracy.

Recent news of another expensive, but highly selective weapon.

https://www.wsj.com/articles/secret...y-terrorists-not-nearby-civilians-11557403411
Secret U.S. Missile Aims to Kill Only Terrorists, Not Nearby Civilians

Weapon doesn’t explode, but brandishes knives to shred target; it was used in high-profile strikes in 2017 and this year

 

[Drakkith]

Why are artillery guns still rifled? You would think it would be cheaper to manufacture and it would get higher muzzle velocity and longer ranges with a smooth bore barrel and discarding sabot fin stabilized projectiles like in anti tank guns.

Discarding sabot rounds are designed for obtaining and retaining high-velocity for their role of armor piercing. Artillery rounds don't require high velocity and the reduced diameter of the sabot round for a given bore diameter would also reduce the explosive payload of the round.

I think it is interesting to watch what happens. If it takes only 1 guided projectile to destroy the target rather than 100 or 1000 dumb ones, then it is probably cheaper, and has fewer incidental victims. The same argument applies to smart bombs, or even to cruise missiles. Expense versus accuracy.

Guided projectiles are great for things like buildings, bunkers, radar stations, and sometimes armored vehicles, but are poor choices for dealing with infantry and large numbers of motorized forces unless they have virtually no air defense.

 

[Stormer]

Discarding sabot rounds are designed for obtaining and retaining high-velocity for their role of armor piercing. Artillery rounds don't require high velocity and the reduced diameter of the sabot round for a given bore diameter would also reduce the explosive payload of the round.

Yes they do require high velocity. That is how they get their range.

And the reduced diameter can be compensated by having a longer projectile so you get the same payload volume in the shell.

 

[Drakkith]

Yes they do require high velocity. That is how they get their range.

No they do not. As an example, the U.S. 155 mm M1 "Long Tom" artillery gun from WW2 has a muzzle velocity of 853 m/s and a modern M777 howitzer has a muzzle velocity of 827 m/s. Most artillery I've looked at has a muzzle velocity around these numbers. In contrast, the General Dynamics KEW-A1 APFSDS round has a muzzle velocity of 1740 m/s, more than twice the M1 artillery shell. Virtually all of the tank KE ammunition on this page have a muzzle velocity around 1700 m/s, far in excess what artillery has.

A muzzle velocity of around 800 m/s is not considered to be high velocity.

 

[boneh3ad]

No they do not. As an example, the U.S. 155 mm M1 "Long Tom" artillery gun from WW2 has a muzzle velocity of 853 m/s and a modern M777 howitzer has a muzzle velocity of 827 m/s. Most artillery I've looked at has a muzzle velocity around these numbers. In contrast, the General Dynamics KEW-A1 APFSDS round has a muzzle velocity of 1740 m/s, more than twice the M1 artillery shell. Virtually all of the tank KE ammunition on this page have a muzzle velocity around 1700 m/s, far in excess what artillery has.

A muzzle velocity of around 800 m/s is not considered to be high velocity.

He's not entirely of base here. A higher muzzle velocity, all else being equal, will generally result in a longer range. The M777 with standard dumb ammunition has roughly equivalent (or slightly less) range than shells fired by the M1. Even the rocket-assisted M549 shells only get slightly greater range because there is only so much room at add a propellant without sacrificing space for warhead.

The M982 Excalibur has longer range but that's in large part because it is finned, which gives it some limited gliding capability (i.e, it isn't purely ballistic).

I believe the main gun on an M1A2 Abrams firing M829 APFSDS rounds still only has an effective range of about 3 km. It only about about 20% as much as a standard M795 howitzer shell, though, so it's easier to get up to those speeds but will slow down more quickly due to drag versus a heavier projectile of the same form. It's not apples-to-apples.

Yes they do require high velocity. That is how they get their range.

And the reduced diameter can be compensated by having a longer projectile so you get the same payload volume in the shell.

Having said all of the above, you can't just go about making artillery rounds shaped like broom handles to try to get the same mass of high explosive, either. The shape of the explosive can matter as much as the quantity. It can affect any shaping the designer wants to do with the blast (e.g., make sure energy is directed toward a target and not everywhere all at once) and can affect aerodynamic stability.

There's also a question of how to transport and load something like that. Breach loading a long rod means you would have to reduce the elevation of your howitzer to fit the shell in the back if it gets too long. That uses up valuable time when rate of fire is a concern.

You'd also have to consider that a longer projectile with a discarding sabot will either have less barrel to travel or would require a longer barrel to make optimal use of the propellant.

 

[Drakkith]

He's not entirely of base here. A higher muzzle velocity, all else being equal, will generally result in a longer range.

Certainly, but the fact remains that artillery doesn't achieve its range by being high-velocity, because it isn't high-velocity. The 700 - 900 m/s 'standard' muzzle velocity range seems to be a sweet spot where you get enough velocity for long effective range while keeping the amount of required propellant and barrel wear to an acceptable level, along with tolerable gun construction costs. To go up in velocity you either need to increase the amount propellant and/or barrel length, which are both serious considerations to take into account, or make your projectile lighter, which reduces its damage potential.

Rifled guns firing shells with a muzzle velocity of around 800 m/s are the standard for a reason.

I believe the main gun on an M1A2 Abrams firing M829 APFSDS rounds still only has an effective range of about 3 km. It only about about 20% as much as a standard M795 howitzer shell, though, so it's easier to get up to those speeds but will slow down more quickly due to drag versus a heavier projectile of the same form. It's not apples-to-apples.

I think the main issue with the Abrams APFSDS round is that it is a fundamentally different type of round than the common artillery rounds. The APFSDS round is designed to penetrate armor using its very high speed. So it has to be nearly pinpoint accurate to hit a relatively small target (vs the use of artillery for area suppression) AND has to retain enough velocity to penetrate an armored vehicle. These two requirements are what limit its effective range, though not its maximum range. The table below shows the velocity of several APFSDS rounds vs range:

As you can see, the rounds are all still well above 800m/s even out to 10km+ in range. However, they've lost roughly 3/4 of their kinetic energy by this point, making them far less effective at penetrating their target's armor. Even dropping from 1700 m/s to 1400 m/s is a reduction of about 1/3 kinetic energy and penetrating power, so by the time the round reaches 4 km it is already substantially less effective.

Finally, the very design of any high-velocity sabot-based round is fundamentally at odds with artillery shell design. Artillery shells want maximum destructive power (or maximum utility for things like smoke or illumination rounds) for a given size, which is achieved by packing as much explosive or other material as possible into the shell. A high-velocity round, especially a sabot-based design, typically does the opposite. It reduces the size and weight of the projectile in order to get that increase in velocity and retain it. Great for KE penetrators, not so great for most everything else. Sure you can make the projectile longer, but then you've just increased the mass again, which brings the velocity back down.

APFSDS rounds aren't high velocity because of their sabot design, they are high-velocity because the round and sabot are extremely lightweight. The M1 Abrams 120mm M829 round has a combined sabot and subprojectile mass of 7.1 kg, of which 4.3 kg is the subprojectile itself. Compare this with the M830 HEAT round which has a projectile weight of 13.5 kg, nearly twice that of the M829 sabot+subprojectile, and a muzzle velocity of 1140 m/s. The M829 also uses 8.1 kg of propellant vs 5.5 kg for the M830. Half the weight plus 50% more propellant is required to get the M829 round up to 1670 m/s vs 1140 m/s using the same gun.

Edit: Forgot to add the M830 muzzle velocity. Added now.

 

[Stormer]

The shape of the explosive can matter as much as the quantity. It can affect any shaping the designer wants to do with the blast (e.g., make sure energy is directed toward a target and not everywhere all at once) and can affect aerodynamic stability.

I thought the point of artillery is to affect a area, so a equal dispersion of frag going in every direction.

And aerodynamic stability is the reason a long slender sabot dart can be shot accurately without spin stabilization. A normal artillery shell on the other hand would tumble without spin stabilization.

Breach loading a long rod means you would have to reduce the elevation of your howitzer to fit the shell in the back if it gets too long.

If you are using a brass case anyway the total length does not have to be so much longer because you can put the sabot projectile all the way down to the bottom of the case with the propellant around it just like in a saboted tank shell.

I also think a slim sabot artillery shell with the same weight as a normal artillery shell would get a better ballistic coefficient and that alone would give it a longer range, plus the higher speed because of no losses going to spinn up the projectile. And all of that with a cheaper barrel to make because of no rifling, and probably a longer barrel life too because of the lack of rifling.

 

[Drakkith]

I also think a slim sabot artillery shell with the same weight as a normal artillery shell would get a better ballistic coefficient and that alone would give it a longer range, plus the higher speed because of no losses going to spinn up the projectile. And all of that with a cheaper barrel to make because of no rifling, and probably a longer barrel life too because of the lack of rifling.

Okay. Let's say you have a barrel that's 150 mm inner diameter. What are the dimensions of your sabot shell? How much explosive does it have in it? What is its approximate muzzle velocity? How does it compare to a normal artillery shell of roughly 150 mm?

 

[boneh3ad]

I thought the point of artillery is to affect a area, so a equal dispersion of frag going in every direction.

Sure, but that doesn't include up and to the sides. If you have a long, rod-shaped projectile, it would be difficult to shape a charge that does anything other than send shrapnel out horizontally when detonated at ground level, when what you really want is an air burst that sends a cone of shrapnel down over a wide area.

And aerodynamic stability is the reason a long slender sabot dart can be shot accurately without spin stabilization. A normal artillery shell on the other hand would tumble without spin stabilization.

You still have to carefully balance that projectile to make sure it is stable, which is not a given if you also have to pack a warhead in there.

If you are using a brass case anyway the total length does not have to be so much longer because you can put the sabot projectile all the way down to the bottom of the case with the propellant around it just like in a saboted tank shell.
View attachment 313857

I also think a slim sabot artillery shell with the same weight as a normal artillery shell would get a better ballistic coefficient and that alone would give it a longer range, plus the higher speed because of no losses going to spinn up the projectile. And all of that with a cheaper barrel to make because of no rifling, and probably a longer barrel life too because of the lack of rifling.

Let's test this theory:

• The penetrator for an M829 APFSDS weighs 4.6 kg and is 68.4 cm long and 2.7 cm in diameter, so the aspect ratio is 25.3. It also has 11.9 kg of propellant and casing.
• The M795 howitzer shell weighs 47 kg, 10.8 kg of which is high explosive.

Let's assume we want the same aspect ratio as the M829 penetrator in the form of a howitzer projectile. TNT has a density of 1.654 g/cm³, so the M795 has 6529.6 cm³ of TNT inside. To mold that into a projectile the same shape as the M829 penetrator (i.e., with the same aspect ratio), it should obey the rule
$$L = \left(\frac{4V(AR)^2}{\pi}\right)^{1/3},$$
which results in a shell that is 174.7 cm long. That's already 1/3 the length of the barrel of the M777. Here's the kicker: you can't just shape the explosive like the penetrator because it's the casing that produces the blast frag effect for an artillery round. I don't have number for how much the casing on an M795 weighs, but it's the majority of the remaining weight of the shell since the propellant charges are separate. Let's assume it's 80% of the remaining 36.2 kg, so about 29 kg of high-frag steel casing. That has to surround the high explosive. It has a density of about 7.85 g/cm³, so the volume is 3694.3 cm³. That makes the total volume of the projectile 10,022 cm³, leading to a length of 203.0 cm. with a diameter of 8.0 cm. That's about 40% the length of the M777 barrel.

Now let's assume the ratio of projectile mass to the total mass of the round (including propellant, casing, and sabot) is the same as for the M829. The M829 weighs 20.9 kg, so is about 43% projectile by mass. This means the above shell with a mass of 39.8 kg would be part of a round whose total mass is 92.6 kg.

So your idea is to launch rods that are taller than an average adult male from a round with a mass that is greater than the average adult male. This is a bad idea for several reasons:

• The round would require de-elevating the howitzer in order to load it, slowing down firing operations.
• The round would not work with existing howitzers, whose barrels are far too short for this.
• The round would require considerably more complicated logistical chains to transport it and deliver it to the battlefield (they are twice the mass and almost 3 times the length but with the same diameter as the M795 in this example).
• The round would require multiple soldiers to lift it and load it into the howitzer, meaning you need more men to man an artillery battery.
• There still isn't likely to be enough room to ideally shape the charge to produce optimal blast frag without further increasing the size and mass.

 

[cjl]

Certainly, but the fact remains that artillery doesn't achieve its range by being high-velocity, because it isn't high-velocity.

That's really all relative though.

Higher velocity means longer range, and the recent trend to go to 52 caliber barrels on things like the PzH-2000, Krab, Caesar, and Archer systems or even the 58 caliber barrel on the M-1299 howitzer the US is testing as part of the Extended Range Cannon Artillery program are perfect examples of this. Of course, these are achieving higher velocity by just lengthening the barrel, because as @boneh3ad explained a sabot round would be wildly impractical for a number of reasons, but this extended barrel rather dramatically increases range - from ~24 km with a normal shell and 35-40 with an Excalibur from an M777 up to 35km normal and 60km Excalibur on the PzH-2000. The M1299 has even successfully completed a 70km test shot with the Excalibur.

Of course, there's a balance here with both barrel wear and practicality (longer barrels make the guns more difficult to transport, maneuver, and just generally make everything more awkward), but it certainly seems that the trend has been towards higher velocity and longer range lately, especially based on learnings from the Ukraine war so far.

 

[Drakkith]

That's really all relative though.

Certainly. Relative to the velocity of artillery rounds, a sabot-based kinetic penetrator round is high velocity. That was the context of what I said in post #37 which started this branch of discussion.

 

[Stormer]

Let's assume we want the same aspect ratio as the M829 penetrator in the form of a howitzer projectile.

Why would you assume that? I would think you want the widest shell possible that can still remain aerodynamically stable and fit in the barrel with the fins (that can be folding). So go as wide as you can until it is starting to show signs of being aerodynamically unstable while still keeping a decent volume for payload, wall thickness and total length with the casing and propellant.

And when it comes to slender darts and fragmentation just look at Starstreak. The subprojectiles there seems to disperse the fragments just fine. And remember that a artillery projectile will never come 90 degrees straight down to the ground so a radial frag pattern will still hit the ground (but maybe as much as almost half the frag can be wasted by going up in the air and loosing to much energy before it comes falling back to the ground).

 

[Drakkith]

And when it comes to slender darts and fragmentation just look at Starstreak. The subprojectiles there seems to disperse the fragments just fine.

Starstreak is an anti-aircraft weapon system. Its subprojectiles are designed to physically impact the target and THEN explode. Since they are already inside the target, and the target is a highly complex piece of machinery that can be mission-killed with very little damage, especially from the inside, the required charge and amount of shrapnel is relatively low. Hence you can use a very slender dart-like projectile with only a pound of explosive.

Artillery shells are usually designed for area suppression, which requires much larger amounts of fragmentation and explosive.

Why would you assume that? I would think you want the widest shell possible that can still remain aerodynamically stable and fit in the barrel with the fins (that can be folding). So go as wide as you can until it is starting to show signs of being aerodynamically unstable while still keeping a decent volume for payload, wall thickness and total length with the casing and propellant.

If you're making the projectile larger, then why have the sabot at all? The entire point of the sabot is to align the projectile with the center of the barrel, capture as much of the force of the propellant as possible, and then drop away so that the thin, high-velocity projectile isn't slowed down by it. That is literally the only point of the sabot. If you're going to make the projectile larger, just make it the same diameter of the bore and be done with it. A sabot doesn't give you high-velocity. A lightweight projectile does.

Note that you don't need a sabot if all you desire is a cheap, smoothbore barrel. They already make artillery shells with fins on them.

And remember that a artilleri projectile will never come 90 degrees straight down to the ground so a radial frag pattern will still hit the ground (but maybe as much as almost half the frag can be wasted by going up in the air and loosing to much energy before it comes falling back to the ground).

That is supported by this article by The Geneva International Centre for Humanitarian Demining (GICHD), entitled Explosive Weapon Effects. From page 52:

The angle at which a munition impacts the target has a significant bearing on the size and shape of the lethal area. In simple terms, the higher the angle (toward vertical 90°) of fall, the larger the lethal area will be.51 In order to maximize lethal area, at higher angles of fall (45-90°) the optimal height for detonation is approximately 2 m above ground, although even at just above ground, the lethal area is increased (Jacobsen & Strømsøe, 1968).

 

[Stormer]

Starstreak is an anti-aircraft weapon system. Its subprojectiles are designed to physically impact the target and THEN explode.

Many AA missiles also have proximity burst. To shower the target with frag.

If you're making the projectile larger, then why have the sabot at all?

Because my point was to make a projectile that did not need spin stabilization to be stable in flight. So you don't waste energy spinning the projectile and therefore getting higher velocity and longer range. And also to get rid of the rifling of the barrel to make it cheaper to manufacture and maybe also give it a longer service life. To get a aerodynamically stable projectile without spin stabilization you need to make it higher aspect ratio and therefore a sabot for it not to need so high chamber pressure to get it up to speed. But you do not need as high of a aspect ratio as a APDS to achieve this. Plus the benefit of getting a higher ballistic coefficient with a higher aspect ratio shell than a normal artillery shell will also increase the range.

 

[Drakkith]

Because my point was to make a projectile that did not need spin stabilization to be stable in flight. So you don't waste energy spinning the projectile and therefore getting higher velocity and longer range. And also to get rid of the rifling of the barrel to make it cheaper to manufacture and maybe also give it a longer service life. To get a aerodynamically stable projectile without spin stabilization you need to make it higher aspect ratio and therefore a sabot for it not to need so high chamber pressure to get it up to speed. But you do not need as high of a aspect ratio as a APDS to achieve this. Plus the benefit of getting a higher ballistic coefficient with a higher aspect ratio shell than a normal artillery shell will also increase the range.

I'm not sure what else to say that hasn't already been said. Choice of projectile shape and size varies widely and takes many factors into account. Standard artillery shells that are spin stabilized have advantages in cost and damage potential, while other rounds have advantages in other areas like range and accuracy. I question whether the advantages of a smoothbore, sabot-based round are worth the added cost and complexity of the rounds and the reduced damage potential. Saving $10,000 per gun (or whatever amount) is all fine and good, but if you're spending 10x more on ammunition you might not be saving anything at all.

 

[boneh3ad]

Many AA missiles also have proximity burst. To shower the target with frag.

1. AA missiles have a very different propulsion mechanism, a very different deployment vehicle, a very different target, and a very different logistical chain than artillery shells. Grenades also shower a target in frag but that is also not relevant here.
2. AA missiles are not as long and slender as an APFSDS penetrator, and even when they are, their size is so much larger that they can still fit plenty of fancy explosives inside.

 

[Stormer]

Standard artillery shells that are spin stabilized have advantages in cost and damage potential, while other rounds have advantages in other areas like range and accuracy.

Yes. But the topic of this thread was to increase the range of artillery. If other aspects like damage potential suffers that is a different topic. And you can have different shells to preform different tasks. And that is another advantage of going with a sabot shell, because that way you still keep the caliber of the gun so you could also shoot a traditionally shaped shell with the same gun with finns to impart the spinn on it for stabilization. So you could have the same smoothbore gun and use the traditional shaped but finned shell for shorter ranges, and use the longer non spinning sabot shell for longer range targets.

 

[boneh3ad]

Yes. But the topic of this thread was to increase the range of artillery. If other aspects like damage potential suffers that is a different topic.

Is it even an artillery shell if it can no longer perform the basic duties of an artillery shell?

On the other hand, you could make a shell of approximately the same size with, say, a ramjet integrated into it and keep the same supply chain and logistics processes in place and use the same guns while still greatly increasing range. It has an advantage over rocket-assisted artillery shells in that it does not carry its oxidizer along with it, leaving more space for payload (though with a loss of some space for the flow path). It's a win-win.

The US Department of Defense is funding exactly that:
https://www.defensenews.com/miltech/2022/08/11/boeing-nammo-test-ramjet-155-artillery-weapon/

 

[Drakkith]

Yes. But the topic of this thread was to increase the range of artillery.

Indeed. But you haven't shown that your method actually increases the range of an artillery shell.

 

[Rive]

I also think a slim sabot artillery shell with the same weight as a normal artillery shell would get a better ballistic coefficient and that alone would give it a longer range,

I'm a bit late to the party with this, but be careful with those darts as references. That whole system is optimized to give insane single point penetration at close (few km) range, and there is very little thought given for anything above 5km.

Also, don't get carried away with those long darts

 

[boneh3ad]

I'm a bit late to the party with this, but be careful with those darts as references. That whole system is optimized to give insane single point penetration at close (few km) range, and there is very little thought given for anything above 5km.

Also, don't get carried away with those long darts
View attachment 313909

...to the last I grapple with thee; from hell's heart I stab at thee; for hate's sake I spit my last breath at thee

 

[Flyboy]

I'm a bit late to the party with this, but be careful with those darts as references. That whole system is optimized to give insane single point penetration at close (few km) range, and there is very little thought given for anything above 5km.

Part of that is also the nature of modern armored combat. Beyond that range, the tank sensors and drew may have difficulty picking out their targets on the battlefield, unless you're up on a ridgeline, hull down in a revetment, and your enemy is making a blind charge across open terrain without artillery or air support.

A proper scenario would probably include things like smoke rounds deploying curtains of smoke to obscure visibility, VT/prox fused artillery barrage of known/suspected tank and infantry emplacements, maybe even MLRS salvos deploying shaped charge and anti-personnel submunitions. If your enemy is really capable, they may even be using standoff air launched ordinance to glide silently over your position and deploy sensor fused weapon submunitions on your position to really ruin your day.

If you're having a good day, you can expect to be making engagements with a modern MBT at 3km tops. Usually that's a third of that or less.

As for the idea of subcaliber tube artillery... I can think of a single practical use for it: extremely long-range strike against a fixed, hardened target like a command and control bunker or similar. But it's a very niche role, that depends heavily on being able to pack the requisite GPS guidance into the round, and knowing exactly where the bunker is, and hoping it's shallow enough you can punch into it.

If you want to hit someone with artillery at a great distance, rockets or missiles are absolutely the way to go. Hell, take a page from the US and slap a small GPS-guided glide bomb atop an existing rocket, give it the target, and just yeet that thing as high and far as you can, then glide from there.

 

[sbrothy]

Why are artillery guns still rifled? You would think it would be cheaper to manufacture and it would get higher muzzle velocity and longer ranges with a smooth bore barrel and discarding sabot fin stabilized projectiles like in anti tank guns.

Long range howitzers are smoothbore exactly because rifling converts some of the projectile's energy to rotation. I read this recently but dont remember where. Must be easy to verify though.

Apropos I also seem to remember that both the US and China has fielded naval railguns. There are some impressive videos on youtube.

 

[Drakkith]

Apropos I also seem to remember that both the US and China has fielded naval railguns. There are some impressive videos on youtube.

I'd say 'tested' instead of 'fielded'. None of these weapons are in operational status as far as I know, and I believe the U.S. Navy has postponed or stopped further research and development on railguns for the moment.

 

[sbrothy]

I'd say 'tested' instead of 'fielded'. None of these weapons are in operational status as far as I know, and I believe the U.S. Navy has postponed or stopped further research and development on railguns for the moment.

You may well be right. Something about the gun's inability to keep shooting no?
edit: https://www.defensenews.com/naval/2...-futuristic-railgun-eyes-hypersonic-missiles/

Also railguns are for space. Can it even fire over the horizon. Nah this one is truly nuts:

Project Thor

Also recently read Stross' Singularity Sky. Concepts like "directional spallation" and "prefragmented copper needles" stuck in one's head. He's good fun.

 

[cjl]

Long range howitzers are smoothbore exactly because rifling converts some of the projectile's energy to rotation. I read this recently but dont remember where. Must be easy to verify though.

This is false. Long range howitzers are still rifled (here's the inside of an M777 for example), albeit with some slight differences in how that works compared to small arms. Rather than the rifling engaging the projectile itself, the projectile is actually sized to be the size of the inside of the rifling, and then it has a larger "driving band" at the base that is made of a soft metal like copper that actually engages with the rifling, allowing the projectile itself to be steel without destroying the rifling in only a couple shots (visible here: https://upload.wikimedia.org/wikipe...t_Desert_Fire_Exercise_130423-M-VH365-119.jpg). In addition, they usually have rifling that starts out with very little twist and then gains twist as you approach the muzzle. This allows the angular acceleration of the projectile to happen more smoothly and puts less stress on the driving band and causes less wear on the rifling than a constant twist rifling like you'd find in small arms.

You're probably thinking of modern tanks, which have almost entirely switched to smoothbore (with the exception of the British Challenger, if I remember right), because apparently spinning projectiles typically have somewhat worse armor penetration and the smoothbore lets them achieve extremely high velocities that let APFSDS (the long narrow finned rounds with discarding sabot discussed above) work to peak effectiveness.

 

[sbrothy]

This is false. Long range howitzers are still rifled (here's the inside of an M777 for example), albeit with some slight differences in how that works compared to small arms. Rather than the rifling engaging the projectile itself, the projectile is actually sized to be the size of the inside of the rifling, and then it has a larger "driving band" at the base that is made of a soft metal like copper that actually engages with the rifling, allowing the projectile itself to be steel without destroying the rifling in only a couple shots (visible here: https://upload.wikimedia.org/wikipe...t_Desert_Fire_Exercise_130423-M-VH365-119.jpg). In addition, they usually have rifling that starts out with very little twist and then gains twist as you approach the muzzle. This allows the angular acceleration of the projectile to happen more smoothly and puts less stress on the driving band and causes less wear on the rifling than a constant twist rifling like you'd find in small arms.

You're probably thinking of modern tanks, which have almost entirely switched to smoothbore (with the exception of the British Challenger, if I remember right), because apparently spinning projectiles typically have somewhat worse armor penetration and the smoothbore lets them achieve extremely high velocities that let APFSDS (the long narrow finned rounds with discarding sabot discussed above) work to peak effectiveness.

I'm sure you're right. In fact I think I managed to find something along the lines of what I had been reading:

It's admittedly a Russian site but the arguments sounds pretty compelling:

"[...] One of the main parameters of any receiver system, including a tank gun, is the so-called. muzzle energy - the energy transmitted by the powder gases to the projectile. In the case of tank guns, muzzle energy is primarily responsible for the firing range and the penetration rate of the target’s armor. It was established a long time ago that a smooth barrel, both in theory and in practice, allows to obtain higher values of muzzle energy in comparison with rifled. A direct consequence of this advantage is an increase in the resource of the trunk with similar characteristics. [...]"

So there.

 

[Mondayman]

You're probably thinking of modern tanks, which have almost entirely switched to smoothbore (with the exception of the British Challenger, if I remember right), because apparently spinning projectiles typically have somewhat worse armor penetration and the smoothbore lets them achieve extremely high velocities that let APFSDS (the long narrow finned rounds with discarding sabot discussed above) work to peak effectiveness.

The Challenger does have a rifled gun. Actually, it is a British Challenger I from the Gulf War that holds the record for the longest tank-on-tank kill. It was at or just under 3 miles I think.

 

[Flyboy]

Also railguns are for space. Can it even fire over the horizon.

Not necessarily restricted to space. And yes, they can absolutely fire over the horizon. To the tune of more than 100 miles range with currently proposed indirect fire railgun concepts. Most of the current applications are direct fire, though, leveraging the higher speed and greater depth of magazine of the railgun compared to the traditional 5" naval gun on most US surface combatants.

You're probably thinking of modern tanks, which have almost entirely switched to smoothbore (with the exception of the British Challenger, if I remember right), because apparently spinning projectiles typically have somewhat worse armor penetration and the smoothbore lets them achieve extremely high velocities that let APFSDS (the long narrow finned rounds with discarding sabot discussed above) work to peak effectiveness.

The spin imparted by rifling disrupts the function of HEAT shells, as the rotation interferes with proper jet formation by the shaped charge. APFSDS would probably care less about rifling.

 

[berkeman]

greater depth of magazine of the railgun

I hadn't heard that term before. What is it?

 

[boneh3ad]

I hadn't heard that term before. What is it?

Railguns fire projectiles that don't require chemical energy to be carried onboard, i.e., they don't need a chemical propellant and usually don't have warheads, instead relying on the kinetic energy associated with their much higher velocities (compared to traditional shells). This means the rounds are a lot smaller and a ship could carry a whole lot more of them. Thus, it has a deeper magazine.

Of course, it takes a lot of power to operate a railgun at scale...

 

[Nik_2213]

IIRC, Battleships' 'big guns' wore sufficiently rapidly that a range of 'driving band' sizes was required...

Also, their gun-laying analogue computers had to include both count and rate of firing, as rapid-fire wore even faster...