Increasing the Range of Howitzers

[chemisthypnos]

I think that the range of a howitzer be increased simply by adding more explosive propellant. Why is this not used? I would think that this would be a straightforward way to increase the gun's effective range. Any ideas?

 

[berkeman]

https://i.pinimg.com/474x/d3/6e/3d/d36e3d20190fe6c218ab092bbbf39dbf.jpg

 

[chemisthypnos]

If the barrel would become too damaged, why don't they just make the walls of the barrel thicker?

 

[boneh3ad]

At some point the weight and expense of everything becomes prohibitive. In theory you could launch a howitzer shell with a nuclear bomb and you'd probably send it darn near into space, but is that really worth it?

Instead, efforts to increase range have focused more on adding things like onboard propulsion and lifting surfaces like fins that allow it to glide and maneuver on the way back down.

 

[anorlunda]

Don't you think that has been thought of before? They tried.

The modern research on long range guns is focused on rail guns, which can shoot much longer range than a cannon with no barrel at all.
https://en.wikipedia.org/wiki/Railgun

 

[DaveE]

Systems, like artillery, are usually designed to meet multiple performance requirements simultaneously (cost, weight, range, etc.). You can seldom make simple assumptions about optimization of one variable in the design process by only considering a single effect.

Look at this picture of a WW2 battleship and ask yourself "Why aren't the guns all the same type?"

 

[Baluncore]

I think that the range of a howitzer be increased simply by adding more explosive propellant.

The "Lyman-Haskell multi-charge gun" increased the amount of explosives by having several separate charges in combustion chambers along the barrel. That was the first of several attempts that included the v3.
https://en.wikipedia.org/wiki/V-3_cannon

The limit to what has been done is probably HARP.
https://en.wikipedia.org/wiki/Project_HARP

 

[trurle]

I think that the range of a howitzer be increased simply by adding more explosive propellant. Why is this not used? I would think that this would be a straightforward way to increase the gun's effective range. Any ideas?

The historical concept of long-range howitzer is called "gun-howitzer". In modern military, most of heavy howitzers are "gun-howitzers" - and their range for base bleed rounds reach 40km. Therefore, statement "Why is this not used?" is incorrect.
For range extension past ~60km, recipe "add more propellant" do not work because the necessary muzzle velocity become comparable with the speed of molecules in propelling gas. Therefore, pressure on base of (shell) drops sharply.

 

[chemisthypnos]

The historical concept of long-range howitzer is called "gun-howitzer". In modern military, most of heavy howitzers are "gun-howitzers" - and their range for base bleed rounds reach 40km. Therefore, statement "Why is this not used?" is incorrect.
For range extension past ~60km, recipe "add more propellant" do not work because the necessary muzzle velocity become comparable with the speed of molecules in propelling gas. Therefore, pressure on base of (shell) drops sharply.

Thank you all for bringing your unique perspectives to this discussion. I have found them all to be most informative. Trurle, you are saying that even if more propellant were to be added, it would not benefit the muzzle velocity past a range of 60 km or so?

 

[cjl]

As trurle mentioned, at some point, there's a limit to range simply because no matter how much propellant you add, the muzzle velocity is limited to approximately the sound speed in the propelling gas (which is much faster than the sound speed in the ambient atmosphere due to the high temperature inside the barrel). Once the projectile reaches this speed, the gas behind it cannot propel it any faster because it's moving as fast as the gas would be if it were just free expanding down the barrel (this isn't exactly the sound speed in the gas, but it's close enough).

The solution to this is to either use propellants with higher molecular velocity in their products (which, functionally, means finding an explosive with lighter mean molecular weight in the products), or to use more complex designs such as the "light gas gun", but we're already basically using the best propellant mix for our considerations of manufacturability, stability/storability, and performance. Light gas guns aren't feasible due to their complexity and the multiple additional components needed (and their much larger size). In addition, to reach these very high velocities, a very long barrel is needed, which hinders the usability of the weapon and makes it far more cumbersome to transport.

Because of these considerations, we've basically settled on ~40km as the maximum reasonable range for howitzers, and beyond that, it's more worthwhile to just switch to rocket artillery rather than trying to further increase the range of guns. That having been said, it is technically possible to exceed 100km range with a gun, it just requires a very large gun, both in the mass of fired projectiles (in order to minimize the effect of air drag) and in length (in order to achieve very high muzzle velocities). You can see this with the German Paris Gun from WWI, which was absolutely massive, despite only being a slightly larger caliber than more modern artillery, due to the incredibly long barrel required to hit the high muzzle velocity needed to have that kind of range. Compare that to more modern rocket artillery that fits on the back of a truck and still is able to achieve over twice the range of even this extreme example.

 

[trurle]

Trurle, you are saying that even if more propellant were to be added, it would not benefit the muzzle velocity past a range of 60 km or so?

Yes, correct.

 

[boneh3ad]

The solution to this is to either use propellants with higher molecular velocity in their products (which, functionally, means finding an explosive with lighter mean molecular weight in the products), or to use more complex designs such as the "light gas gun", but we're already basically using the best propellant mix for our considerations of manufacturability, stability/storability, and performance. Light gas guns aren't feasible due to their complexity and the multiple additional components needed (and their much larger size). In addition, to reach these very high velocities, a very long barrel is needed, which hinders the usability of the weapon and makes it far more cumbersome to transport.

Consider that the G range light gas gun at AEDC, which is the largest continuously operated in the US, can accelerate a projectile up to 7 km/s but it maxes out at an 8 inch projectile and usually operates with something closer to 4 inches. This requires a barrel that is 100+ feet long and uses fun and safe gases like hydrogen. It's a really flipping cool facility, though. Everyone should definitely go look it up.

Because of these considerations, we've basically settled on ~40km as the maximum reasonable range for howitzers, and beyond that, it's more worthwhile to just switch to rocket artillery rather than trying to further increase the range of guns. That having been said, it is technically possible to exceed 100km range with a gun, it just requires a very large gun, both in the mass of fired projectiles (in order to minimize the effect of air drag) and in length (in order to achieve very high muzzle velocities). You can see this with the German Paris Gun from WWI, which was absolutely massive, despite only being a slightly larger caliber than more modern artillery, due to the incredibly long barrel required to hit the high muzzle velocity needed to have that kind of range. Compare that to more modern rocket artillery that fits on the back of a truck and still is able to achieve over twice the range of even this extreme example.

You could also try this: https://www.thedrive.com/the-war-zo...rtillery-shell-and-it-could-be-a-game-changer

 

[Drakkith]

I think that the range of a howitzer be increased simply by adding more explosive propellant. Why is this not used? I would think that this would be a straightforward way to increase the gun's effective range. Any ideas?

In addition to what's already been said, remember that increasing the range of a gun does not necessarily increase its effective range. Placing an unguided projectile on-target is difficult, and only gets more so as the range increases. So even if you could increase the range of a projectile by simply increasing the propellant, you may find that your accuracy has decreased far too much for the gun to be useful at that range.

Also, adding propellant increases the weight and size of the shells (or the number of bagged propellant charges used), which reduces the number of rounds a gun/battery/ship is able to carry at once, and also costs more per round. So if you're not confident that your guns can accurately fire out beyond a certain distance then you're probably better off reducing the propellant so you can have more rounds to fire.

 

[Vanadium 50]

I was about to make a similar comment to Drakkith. Being able to miss at increased range is not so effective.

 

[chemisthypnos]

Those are very good points, everyone. If I may ask another question, does the current quantity of propellant reach the speed of sound of that gas at the elevated temperature of its ignition? If so, then adding additional propellant would be pointless.

 

[cjl]

Most current guns operate at a muzzle velocity of around half of what they would be capable of based on that limit. With normal propellants, that limit is ~5000-6000 ft/s, but muzzle velocities around 3000 ft/s are more common, for the other practical reasons mentioned above (also, at very high velocities, barrel wear becomes an increasing concern).

 

[Drakkith]

Those are very good points, everyone. If I may ask another question, does the current quantity of propellant reach the speed of sound of that gas at the elevated temperature of its ignition? If so, then adding additional propellant would be pointless.

It's really about the speed of the projectile, as the gas can't expand down the barrel faster than the projectile is moving. In any case, the answer is no, not in the vast majority of guns, especially for artillery and small arms. You typically need very long barrels and lightweight projectiles to reach the maximum possible muzzle velocity, both of which are not particularly suited for weapons of war. Longer barrels mean heavier guns while lightweight shells have greatly reduced explosive payload, penetration capability, and may have poorer ballistics. The only real exceptions might be anti-tank weapons that rely on pure kinetic energy to inflict their damage.

Wikipedia shows that the Ordnance QF 17-pounder anti-tank gun had a muzzle velocity of 3950 ft/s for its APDS (Armour-piercing discarding sabot) ammunition and its successor, the QF 20, approached 4700 ft/s. This appears to be much higher than other types of ammunition, especially for non-anti-tank weapons. As a comparison, the HE round from the QF 17 has a muzzle velocity of about 2900 ft/s (1975 ft/s for the QF 20) and the L118 howitzer, a lightweight towed artillery piece, is around 2320 ft/s.

A quick look at a dozen or so different artillery pieces showed me that the muzzle velocities occupied a range between around 1,000 to 2300 ft/s for howitzers and other similar types of artillery pieces.

 

[Baluncore]

To avoid destroying the gun, the propellant charge is designed to burn at a limited rate, while the explosive shell is designed to detonate at the maximum possible rate. When a gun barrel bursts, the material bulges or splits along the barrel because the hoop stress due to internal pressure is twice the elongation stress.

Regarding the picture of a burst gun in post #2. It looks to me like a high explosive shell in the gun detonated prematurely, maybe an instant after the gun propellant was fired. That would explain the position of the damage and the unusual character of the fracture.

The barrels of the biggest naval guns were built up by shrinking progressively larger steel tubes onto the inner liner. By crushing the inner liner, the internal gas pressure could be doubled.

The “Paris Gun”, and other long-range guns where the target was a large civilian area, only needed crude accuracy as they were terror weapons.

 

[Tom.G]

Slightly off subject at the other end of the size range.

Having grown up living in a rural area, I was familiar with .22 caliber rifles. If you used 22LR ammunition (LR = Long Rifle cartridge) you could here hear the supersonic shock until the round hit something.

Being curious, I just asked Google about the muzzle velocity and found that the current high-tech approach is a round made of a polymer and Copper dust. It's a hollow-point that travels at 1850fps, roughly mach 1.7.

The general warning on the several decades old technology was "Lethal at 1 mile."

https://www.google.com/search?&q=highest+muzzle+velocity+.22lr

Cheers,
Tom

 

[cjl]

Worth mentioning that .22LR is actually pretty low velocity as rifle rounds go. The fastest current 22 ammunition (that I'm aware of) is the 220 Swift, which can achieve over 4200 ft/s.

 

[berkeman]

If you used 22LR ammunition (LR = Long Rifle cartridge) you could here hear the supersonic shock until the round hit something.

Yeah, I've had .22 rounds "crack" by me a couple times when hunting as a teenager (when somebody else in the hunting group didn't realize where you were). Pretty un-nerving...

 

[gary350]

I did long range target shooting years ago with a 300 Winchester magnum rifle there is more to it than adding more propellant. Gun barrel & receiver are engineered to handle a certain amount of psi in the chamber. If you exceed the chamber psi the gun explodes. Typical way to increase artillery range is replace gun barrel with a longer gun barrel or add an extension to the original gun barrel.

Next you use a different propellant that burns slower. Assume the original gun barrel was 10 ft long and propellant burns 90% of the gun barrel length. Propellant burns up in 9 ft to get projectile up to full speed 3600 ft per second. If new gun barrel is 15 ft long propellent needs to have projectile up to full speed in 14 ft. A 20% more slower burning propeller is uses so not to explode the gun barrel psi rating the slow propellant burns like a hard push not like a BIG hammer with the other propellant. PSI inside the gun barrel remains the same but propellant burns for several micro seconds longer this gives the propellant more time to get the projectile up to a fastest speed in a distance of 14 ft. Assume projectile speed is increased to 4300 ft per second this is 19.44% faster than before. Maximum artillery range is shot at a 45 degree angle if the original gun could shoot 10 miles the new gun will shoot 11.94 miles.

Factory load rifle bullets propellant burns up in 14" of the 28" barrel length that is why recoil hammers your shoulder so hard. I reloaded my own bullets using a slower powder that burned 26" of the 28" barrel length. Gun recoil was less painful on my shoulder than before. I put lead in the stock to make total gun weight 8 lbs. I changed to a 4 power scope. I tested several shape bullets and several weight bullets. 150 grain bullets pick up speed quick but loose speed quick too. 180 grain bullets increase speed slower but heaver bullets maintain speed longer but gravity pulls them down sooner. 170, 165, 160 grain bullets were all tested for best accuracy and range. As it turned out 165 grain was best. Each projectile needs to be inspected for scratches & tiny dents.

I zeroed my scope at 200 yard, bullet shot 1" low at 100 yards, 0 at 200 yards, 1" low at 300 yards, 2" low at 400 yards, 4" low at 500 yards. I could shoot anything I could see very easy up to 1/2 mile. I use to fill 100 empty soft drink bottles with water and shoot all 100 bottles and not miss from 1/4 mile. 1/2 mile was a tiny bit harder to do. With a tiny bit more practice targets 1 mile away are not hard to hit. Long range shots you need to consider wind speed and Earth rotation it takes the bullet 1.6 seconds to go 1 mile.

If you want to do some very challenging target shooting put a high power rifle scope on a pellet rifle gun has a very good range of 100 ft, 125 ft is harder, bullet drops fast after 150 ft, if you can hit targets at 200 ft targets you are doing very good.

 

[gary350]

Germany developed big guns during WWI and used the same big guns during WWII and made many improvements. Japan made the largest big gun for battle ships 2500 lb projectile had a range of 30 miles. German battle ships shot 2000 lb projectiles with a range of about 25 miles. Rail guns had a range of 20 to 30 miles. Later in WWII Germany experimented with lighter weight projectiles and reached a range of 75 to 128 miles with rail guns. During WWII Germany developed a big gun barrel 200 ft long but before it could be used the facility was bombed and destroyed.

After the war USA did research with the 200 ft big guns and decided it was not practical it could put a bullet in orbit around Earth and shoot bullets 2500 miles but the gun barrel was stationary and only shot bullets in one direction. The 200 ft long gun barrels were mounting on the side of steep hills to fire projectiles at a certain town 1000+ miles away. Germany put several 200 ft long gun barrels in 45 degree angle tunnels down in the ground it would take a gun crew of about 2000 men to fire and maintain those guns.

Airplanes and cruise missiles make all big guns useless. The 200 ft long gun barrel used about 10 propellant charges they all went off in 1,2,3,4, order very fast to help increase the projectile speed. Modern day artillery has rocket assisted projectiles and GPS guided projectiles that can shoot over mountains turn around 180 degrees and hit objects on the back side of the mountain and shoot right down the entrance hole of a cave. If you want to learn first hand about artillery join the military and sign up for mobile artillery.

 

[Vanadium 50]

Japan made the largest big gun for battle ships 2500 lb projectile had a range of 30 miles.

For all the good it did them. One set of these guns is at the bottom of the Sibuyan Sea, and the other is at the bottom of the East China Sea.

 

[chemisthypnos]

Thank you all for your perspectives. You have all done a great job in helping me to understand this phenomena better.

 

[Brocklion]

A consideration that I have not seen mentioned is useful life of the barrel. At some point the gun becomes less accurate because of wear on the barrel and the gun should be removed from service to have its barrel replaced or refurbished. Detailed records of use of the gun are kept in order to determine when service is needed but, in general, the bigger the charge the more wear is counted and the sooner refurbishment is called for.

 

[Hornbein]

A consideration that I have not seen mentioned is useful life of the barrel. At some point the gun becomes less accurate because of wear on the barrel and the gun should be removed from service to have its barrel replaced or refurbished. Detailed records of use of the gun are kept in order to determine when service is needed but, in general, the bigger the charge the more wear is counted and the sooner refurbishment is called for.

The World War One Paris siege gun had to have its barrel replaced frequently. Every ten shots?

 

[gary350]

WWI Paris gun the original bullet wt was 234 lbs range was 65 miles. Later Germany make several more lighter weight bullets. Each lighter weight bullet traveled farter, 75 miles, 85, miles, 90 miles, 100 miles, 125 miles. I have forgotten a lot of this info I think the 75 lb bullet went 125 miles. Most artillery max range is with gun barrel at 45 degrees but Paris gun max range was at 55 degree barrel angle. Bullet went up to a crazy height of about 60 miles before it started coming down. The gun barrel was good for about 200 shots. Germans learned it was easier to shoot larger diameter bullets than to change the warn out gun barrel. It took the 75 lb bullet about 12 minutes to travel 125 miles.

There are amazing videos on YouTube. Battle ship big guns were the most amazing they shood a 3000 lb bullet 24 miles. Video taken from the German battle ship shows the bullet in the air for about 20 seconds before it hits the target. B52 bombers show videos of the bullets coming up 5 miles bullets look like they are floating up it looks so strange as the bullets get closer.

https://en.wikipedia.org/wiki/Paris_Gun

 

[Drakkith]

WWI Paris gun the original bullet wt was 234 lbs range was 65 miles.

Muzzle velocity of 5400 ft/s! That's absurd! No wonder it had such a long range, especially for an 8 to 9inch shell. I guess that's what a barrel length of 100 calibers will do!

For comparison, the 16" 50-caliber Mk7 guns on the Iowa class battleships threw a high explosive HC Mk 13 shell at only 2690 ft/s at most, reaching out to a maximum range of 38,000 meters (23.6 miles).

http://www.navweaps.com/Weapons/WNUS_16-50_mk7.php

 

[Melbourne Guy]

180 grain bullets increase speed slower but heaver bullets maintain speed longer but gravity pulls them down sooner.

Does gravity work like that, @gary350? I thought things fall at the same rate, irrespective of their mass, so wouldn't it be some other factor reducing their range (if that's the outcome, I think that's what you're saying)?

 

[DaveE]

so wouldn't it be some other factor reducing their range

Like air resistance? IDK, it's an easier problem in a vacuum.

 

[boneh3ad]

...heaver bullets maintain speed longer but gravity pulls them down sooner.

 

[cjl]

Does gravity work like that, @gary350? I thought things fall at the same rate, irrespective of their mass, so wouldn't it be some other factor reducing their range (if that's the outcome, I think that's what you're saying)?

I think what he's trying to say is that with a heavier bullet, the muzzle velocity is slower so the time of flight out to a fixed range is longer. Since you usually don't care about how much the bullet drops in a given time, you care how much it drops at a given range, this means that a heavier bullet suffers more bullet drop (but retains a higher percentage of initial velocity and energy).

 

[Stormer]

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.

 

[cjl]

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.

Sure, you could do that, but that significantly decreases the size of projectile (and thus quantity of explosive filler). In addition, spinning a projectile tends to reduce dispersion compared to a fin stabilized non-spinning one, though you could angle the fins a bit to induce spin that way.

That having been said, some guided artillery rounds with pop-out fins do exist (such as the M982 Excalibur), and if those become close to ubiquitous in the future, smoothbore could end up being a possibility. They are quite expensive though, so I'm not sure they'll ever entirely replace older style unguided shells.

 

[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
<br /> L = \left(\frac{4V(AR)^2}{\pi}\right)^{1/3},<br />
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.