Increasing the Range of Howitzers

[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...