A very nice article discussing Tank Rounds
Link:
USS Clueless - More on the T-72
Rifle vs Smoothbore
Rifled guns are more accurate.
By the late 1960's when the T-72 was in design, the advantages of smoothbore guns were apparent. But the Soviet implementation was incomplete. The advantage of rifling is accuracy; the projectile stays oriented in the direction of flight and doesn't slew as much. A projectile fired from a smoothbore gun doesn't stabilize itself as much and is less accurate.
The other piece which is needed to make this work is, for lack of a better term, "avionics". (We need a term like avionics to apply to tanks.) You have to have a better targeting system. You need sophisticated electronics to aim the gun and compensate for all the things which could cause the projectile to miss, and the M1 has it. The firing system on the M1 is unbelievably sophisticated, with many different sensors and highly complex algorithms. It does things like keep count of the number of rounds fired from the gun, to calculate the effects of wear on the inside of the barrel. It has a direct sensor to measure how much the barrel is sagging. It's doing a lot of other things, too, which they won't tell us about. They can fire it while moving rapidly over broken terrain and score a direct hit on a target which is also moving, at very long range. That's non-trivial.
The M1's gun is uncannily accurate. The T-72's gun isn't. The targeting system in it isn't up to the job. It's not that I think that switching to a smoothbore gun was wrong because rifling is superior, but rather that I think they switched to a smoothbore gun before they had all the pieces to do it right.
The T-72's smoothbore gun is also inaccurate firing HE; a rifled gun would be much better. By switching to a smoothbore gun before they had a targeting system that could make it work, what they did was to pull most of the teeth on their newest tank.
On HEAT from a Rifle
@Keshav Murali, you said that the spinning of the projectile disturbs the charge. I do not think so. The charge is usually of very high viscosity, and for the short few seconds it gets to spin, it cannot disturb that dough like substance. The reason is below:
First, what HEAT forms is a jet of molten copper, rather than a jet of plasma. The forward surface of the shaped charge is a cone-shaped cavity, and it's covered with a thin layer of copper. The power of the charge melts the copper and the wave dynamics of the shape of the charge squeezes the copper together and then squirts it out forward, at extremely high speed.
I did not know that in fact HEAT rounds also work better when they're not spinning very fast. Apparently the spin interferes somewhat with the formation of the molten copper jet, and HEAT rounds intended for rifled guns also use things like plastic sleeves. It is HESH rounds that benefit most from use of a rifled gun.
On Sabot
Should give an indication why Sabot manufacturing needs a lot of precision engineering, and why it is expensive.
With a sabot round, the size of the pencil is not related to the caliber of the gun barrel. (And there's an optimum size for the penetrator; making it bigger may decrease its effectiveness.) In the shell, the penetrator is surrounded on both sides by two half-cylinders, the sabots, which seal the gun barrel so that the power of the shell's charge can be efficiently converted into kinetic energy. Once the round emerges from the gun barrel, the sabots fall away (which is why they're known as "discarding sabots") leaving the projectile to fly on its way to the target. The trick is making the sabots discard cleanly without deflecting the projectile.
Ståle claims that sabot rounds can't be fired out of a rifled gun. That's not actually true. The original 105 mm gun for the M1 was rifled and could fire sabot rounds.
Why Indian Army loves HESH
This is what
@Keshav Murali said, and is confirmed by the reason below.
But there's more to it than that. Everyone concentrates on tank-versus-tank, but most tanks spend most of their time firing at other things, usually ones which aren't moving, and against those they usually fire HE. When a tank is shooting at a pillbox, or a machine gun nest, or a building, or a concentration of enemy infantry in hard cover, they shoot good old high explosive.
Why Depleted Uranium is best for Sabot Rounds
I had mentioned this earlier in the other thread (Link:
http://defenceforumindia.com/forum/...e-tanks-armour-technology-361.html#post716392) the reason is it undergoes adiabatic change. The explanation below is a much better one:
The primary reason why depleted uranium is such a good choice as a material for penetrator darts is that it is self-sharpening. Penetrators made of steel or tungsten compress when they strike armor, and the tip which begins sharp becomes wide and blunt, which drastically decreases its ability to penetrate. Uranium, on the other hand, burns/melts away and the tip of the penetrator remains sharp. It's also more dense which means you can put more mass in the penetrator without making it physically bigger and altering its aerodynamic characteristics.
Chobham armour, what is it?
I have read so many articles using this term that it is now generally accepted as correct, and I have to say, Wikipedia is also correct, as we should just get used to it. I know
@Damian would differ,but it is the way it is. Not denying "Burlington" either. Also,
@average american, those terms mentioned by
@Damian are correct (from a different source), but the name Chobham has stuck, just like the term "Indian" has stuck for the Native Americans. No more fighting over it. Let's move on.
In the 1960's, a British research group located in Chobham, England, began to reconsider the entire concept of steel plate for armor. There had been improvements in the quality of the steel and the way it was forged which had improved its resistance some, but that was a matter of diminishing returns, and just piling more metal on was also subject to diminishing returns. So the Chobham group started over. They came up with an entirely new concept, which is now known as Chobham armor, which was shared with their allies including us. All modern NATO tanks, including the M1, use it and that's the reason they all seem to be kind of boxy, with facets and angles, instead of the curves of earlier tanks like the M-60. Chobham armor has to be created in plates and fitted together. The details of Chobham armor are classified but the general approach is known: it is a series of layers of steel, ceramic and air gaps.
Edit: According to one tank commander of the M1, the M1 can fire on the move at the speed of 30-35 mph and get a first round hit. It is unclear whether the M1 perform well enough at speeds above that. (see spoiler below)
Additional Reference:
[HR][/HR]
So,
@Keshav Murali asked a question whether we should stick to HESH and HEAT, or should we invest more in Sabots. What is your opinion
@Kunal Biswas?
