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Howitzers (like the pictured Bhim) fire their shells at a steep angle into a high parabolic trajectory. They are also long range guns which is why they tend to have longer barrels.<P>The gizmo at the end is like a sleeve with a transverse thro hole. This allows the high pressure explosive gases propelling the shell to expand uniformly to either side as the shell exits the barrel. This prevents the shell from tumbling, making it more stable and therefore more accurate.<P>Tanks etc fire their shells in a flat trajectory to a range of say 2-4000 meters thro a rifled barrel, so they dont need the gizmo at the tip.<P>Submachine guns do have this gizmo at the tip to prevent the shells from tumbling. I dont know what the official name for this gizmo is.
I think they're flash suppressors.<P>- aha just saw Sukumar's note - he's probably right.<P>The long barrel bit is interesting. I remember reading about the ideal propellant for any projectile - it should not be a rapid explosive like a warhead, but should burn relatively slowly so that the shell is gradually be accelerated up the barrel - and with such a propellant - the shell keeps accelerating all the way upto the end.<P>Interesting stuff this business - but looks like I'll never get deep into it in my lifetime.<p>[This message has been edited by shiv (edited 13-11-1999).]
Hey shiv, thats a very nice illustration of what Suku was saying!<BR>What 'charge' is used in modern artillery pieces? I had heard (rather read at army-technology.com) that some guns still use semi-liquid gel charges.
Siddharth, I dont know (for sure) if howitzer barrels are rifled. I think they are smoothbore. I think the spin imparted to the round with rifling is important for stability only in a flat trajectory.<P>A shell flying in a high parabolic arc is more like a missile. Nice pic Shiv.
Vinodji and Prakash - i think Vinodji's message was a joke related to another thread.<P>However, to avoid misunderstanding, I have deleted both your messages.<P>Regarding the "good pic" - i'ts from the B-R Kargil picture collection.
Hi,<P>Siddharth, look at the picture posted by shiv - its almost perfect for my explanation. Its simple newtonian mechanics actually. Consider a barrel without a muzzle break, the exhaust gases leave the barrel directly away from the gun and the gun platform receives a hefty kickback (law of conservation of momentum). On a barrel with a muzzle break, the exhaust gases escape through the side sleeves in a direction perpendicular to the barrel (the expading cloud in the pic) and all the circular sideways momentum imparted to the cloud cancels each other out and results in a overall smaller kickback.<P>I dont agree with sukumars explanation that they actually serve to improve accuracy or stop them from tumbling. Actually they tend to do quite the opposite if you stop to think about it. The overall circular discharge is never quite symmetrical, a little impreceptable imbalance in the radial discharge can and does tend to swing the gun/barrel from side to side leading to inaccuracies, but these are most often very small and adequate tradeoff for lesser recoil.<P>Sukumar, Tanks are almost never have rifled barrels. If you look at most of the mainstream MBT's Abrams, Ariete, Leopard, LeClerc, T-72/80/90 etc, they all have smoothbore barrels. The only exception to this rule are the british tanks, the challenger series for example is fitted with a rifled gun.<BR><p>[This message has been edited by Badar (edited 14-11-1999).]
OK, after a little bit of research, this is what I found out:<P><B>The physics in a muzzle brake</B><P>The recoil of the conventional gun is the<BR>sum of the impulses imparted to the projectile and the propellant gas. For velocities near 1000 m/s, recoil impulse associated with the propellant gas is about 30% of the total. As the launch velocity increases, the charge to mass ratio increases and so too does this percentage. One saving grace of the conventional gun is that a muzzle brake may be employed to recover momentum from the exhausting propellant gas. Typical brake efficiencies range from 50-125%. The latter value meaning that by turning and expanding the propellant gases, more momentum is recovered in the forward direction than they imparted in the rearward direction in accelerating to muzzle exit. The muzzle brake has the drawback of increasing blast overpressure behind the muzzle.<P>This physics has different benefits for different weapons:<P><B>Benefits On Artillery</B><BR>1. Higher muzzle velocity for the shell (longer range).<BR>2. Higher stability to the shell (better range and accuracy).<BR>3. Improved recoil in sustained fire mode (the energy is instead translated to higher muzzle velocity).<P>Overall, a more longer ranged and accurate gun.<P>There <B>are</B> some tank cannons with muzzle brakes, though these are predominantly found on artillery pieces (towed and self propelled).<P><B>Benefits on rifles and small arms</B><BR>Holes are drilled all over the barrel or as a slot or sometimes only in the upper half of the barrel.<BR>1. Improved muzzle velocity.<BR>2. Reduction in recoil (or kick) to the firer by as much as 50-70%.<BR>3. Decreases the tendency of the gun to kick up - therefore accuracy is better.<BR>4. Suppression of muzzle flash.<P><B>Rifled Vs Smooth Bore</B><BR>This is an engineering decision made by the gun designer. Just as we cannot say that all cars are front wheeled drive, it is impossible to generalize that a certain type of artillery is smooth bored.<P>While rifling imparts a spin to the round and hence stabilizes it, it also causes a reduction in effective muzzle velocity which means a decreased range. So if a gun designer can find other means of stabilizing a round, it makes sense to go for a smooth bore.<P>The battleships of the line had massive guns (16 inch guns on the Iowa for example) which were rifled guns. <p>[This message has been edited by R Sukumar (edited 14-11-1999).]
Sukumar thank you, you saved me a post on muzzle brakes. To answer your question, all howitzers since the end of the 19th century have been rifled- widespread use of rifling coincided with the replacement of cannonballs and grapeshot with breech-loaded shells. Rifling was known much earlier than that, but the metallurgy wasn't up to spec at the time- grooves in brass cannon quickly wore out, and cast iron was expensive and had a tendancy to burst. Tumbling wasn't such a terrible thing either for spherical shot as it was for streamlined shells when it came to range and accuracy. <P>Caliber, when used in reference to artillery barrels is actually measured from the bottom of one end of the rifling to the other (at least in the West- the Soviets/Russians measure it from the 'top' of the rifling to the other top)<P> As for tanks, the smoothbore gun was introduced for two different reasons; in the Soviets case so that missiles could be launched, and in Rheinmetall's case for best results with sabot rounds. The problem wasn't range per se- it was the APFDS penetrator's loss of energy to spin at a given range range. <P> Rifled guns are in fact generally more accurate and offer longer ranges- which is why the British retained it. In fact, the longest range confirmed tank kill on record was a Challenger during the Gulf War, which engaged and destroyed a T-55 at 5 miles with a HESH round. APFSDS can be fired from rifled guns so long as they are fitted with slip rings to counteract the spinning.<p>[This message has been edited by Johann (edited 15-11-1999).]
Agree with Johann, howitzer barrels are rifled. Perhaps the confusion arose because someone was thinking of mortars, which are very high trajejectory weapons with smooth bores. Extending that to the fact that howitzers are also high-trajectory weapons, the wrong conclusion was presumably drawn about howitzer barrels.<P>During the Seventies and Eighties there was an active debate among NATO tank-producing countries as to whether smooth or rifled bores were best for best MBT main guns.<BR><p>[This message has been edited by Mohan Raju (edited 15-11-1999).]
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