To add to xeric's point above, another huge quality consideration for artillery barrels is that they are expected to have a greater life (more rounds fired than tank guns) than those designed for armour (and for the reasons highlighted by Xeric).
How could i miss this
I realize this may be taxing because interested persons can do research, however, if and when you have time, would appreciate some elaboration and detail - much obliged
Twaday wastay taim he taim hai sir jee..
Ok let me try explaining this with as much less technicality as possible.
Tanks are direct firing weapons. They aim just like one aims a rifle or pistol and fire. Now this entails less technicality when it comes to working of firing data (the data or calculations required to enable a gun to place the ordnance as close to the target as possible) i.e you aim and fire, may be you need to put in a little right or left corrections and that's it. This coupled with the VERY HIGH muzzle velocity of a tank projectile (i.e. it travels through the air for a very small period), the effects of
External ballistics (
is the part of the science of ballistics that deals with the behaviour of a non-powered projectile in flight, and deals with the behaviour of the bullet after it exits the barrel and before it hits the target - Wiki) is
minimal and the effect of
Internal ballistics, (
a subfield of ballistics, is the study of a projectile's behavior from the time its propellant's igniter is initiated until it exits the gun barrel. The study of internal ballistics is important to designers and users of firearms of all types, from small-bore Olympic rifles and pistols, to high-tech artillery - Wiki) is negligible. (i have skipped the step of Intermediate Ballistics for your easy comprehension). Also, as the max range a tank projectile has to travel (~1-5) is not even 1/4 of that which an artillery's projectile has to travel (12-50 kms), plus a tank projectile is traveling near the ground level (may be around you height) but as an artillery projectile has to follow a pronounced trajectory (parabola) which passes through the troposphere (and can go up to stratosphere) the effect of meteorological conditions plays a significant role in their ballistics - this is where intermediate, external, terminal and wound ballistics comes into play.
Now in order to make an artillery round to behave (as per your wishes) while it travels from Murike to Gujranwala and passes through varying levels of humidity, viscosity, density, temperature of air, and wind speed (as it goes up may be like in KMs) you need a barrel that is
consistent in its properties. Gunners prefer CONSISTENCY over ACCURACY when it comes to their guns. Why? Well, which guns will you prefer when there are 4 guns each of them very accurate(i.e. fires at the same place where aimed at) but when fired repeatedly changes their level of accuracy as the barrel heats (due to excessive fire or external heat) or cools, this will also mean that when all guns fired together they will scatter the fall of shot randomly (not guud as artillery fire in groups not individually). Now compare this with other 4 guns which are not accurate (i.e their aiming sights are not properly calibrated) but they fire exactly at the same place (whether aiming towards it or not) every and any number of times they are fired, this include the heating or cooling of barrel effect - these guns are consistent. Here's where internal ballistics comes into play. Tanks barrels needs to be accurate, artillery barrels needs to be consistent. Ok, enough of consist vs accrac.
Now it may not be possible to make a perfect barrel. A difference in terms of micrometers in the diameter (caliber) of a barrel (due to wear n tear or heat etc) will result into a difference in hundreds of meters at the fall-of-shot (target) end when the round has travel several kilometers between the gun position and the target. Same will happen if the propellent charge (the thing that fires the shell out of the cartridge) is kept under sunlight or shade - a minor difference in charge temperature will either cause the propellent to burn at a faster rate (thus increasing the muzzle velocity and increasing the range) or a lower rate (thus decreasing the range). These are only two minor factors, there are 10s other that affects a shell traveling over KMs.
Now as i said earlier that it may not be possible to make a perfect barrel but it is possible to find out efficiency (the way it will behave etc) of a barrel 'perfectly'. This is where Firing Tables come in. FTs are a collection of data regarding a barrel which tells a gunner how the barrel will behave under standard conditions and also when you increase/decrease the charge temperature in XYZ degrees (unwittingly), or when the humidity increase in XYZ % at ground level or when the weight of a projectile is a few Grams more or less than the standard weight (all projectiles are never of the same weight - they are not sniper bullets in which grains of explosives are counted not filled in term of weight) etc etc. Now these variations are not constant i.e. if the temperature is 1 degree C lower than the standard temperature at which the barrel was tested so this might mean that the FT might tell you that this change will let the shell travel 10 Kms at an elevation of 123 Mils (a unit of circular measurement) instead of 9.8 Kms ( a difference of 200 meters) but this would not automatically mean a change of 2 degree C will cause the shell to travel 400 meter further, the change in range may be 600 or 300 meters this time. This was for range only, a FT must tell this about everything i.e. what effect the changes will have on Deflection, Site, Angle of fall of shot (so that the shell doesnt ricochet and harm the civilians/friendly forces), muzzle velocity, vertex of trajectory, what should you do if you want to conduct High Angle Fire (i.e. for same range you want the shell to travel up higher then normal so that you can clear Tiger Hill and hit an indian HQ in the rear - just an example guy, so chill), what to do if Tiger Hill is occupied by own forces and you want to fire *** fuses (that explode in air after they emit radio signals that bounce back take from ground thus resulting in an air-burst munition) and you want to make sure that the*** fuzed shell doesnt explode overhead own troops occupying the Hill as the height of the hill may cause the signal to bounce nack prematurely thus making it explode, now the same shell would require a different data if fired with a normal fuze and when fired with the *** fuze. This
sainse you will get from the FTs.
In short, wring firing tables can consume 100s of barrels just to validate a single factor (charge temperature/humidity etc).
BTW, as Blain said:[/QUOTE]Building on this success, perhaps we will see HMC producing not only smooth bore guns, but also rifled.[/QUOTE]
Why? Because artillery guns are supposed to be rifled so that an absolute spin is imparted in the shell for better stability and consistency of the shell traveling across several Kms. Tank dont necessarily needs rifled bores. Also because very high velocity of tank shells will damage the rifling.
P.S. Ufff itna lamba hogaya
lechkar.....