Guest Pillar Posted July 12, 2000 Share Posted July 12, 2000 .50 Calibre, 9mm, 88mm guns, 81mm mortars... What is the size refering to exactly? The length? Radius? Thanks for the help. Link to comment Share on other sites More sharing options...
:USERNAME: Posted July 12, 2000 Share Posted July 12, 2000 All diameters. calibers are 1/100 of an inch, so 50 cal half inch diameter and also = 12.7 mm BTW 9mm, 81mm, etc diameter metric system. Link to comment Share on other sites More sharing options...
Jeff Heidman Posted July 12, 2000 Share Posted July 12, 2000 A lot of times, when discussing calibers of guns, you will see a number expressed like 75L38 or 88L71. Sadly, CM elects not to do this, which is too bad. The first number is the diameter (usually in mm) of the round, the second number describes the length of the barrel in units of the previous number. For example, the American 75L38 mounted on the basic M4 Sherman had a 75mm round with a barrel length of 75mm*38=2.85m. Note that this is length from bore to muzzle, so the some of that length on a tank is inside the mantle, and hence not actually seen. Why is this important you might ask? Generally, the longer the barrel, the higher the velocity of the round. Which is why the American 75L38 is a joke as an AT weapon, and the German 75L70 (5.25m) is an extremely potent AT weapon. This also explains why the German 75L70 had much better AT performance than the Soviet 85mm on the T-34, which I *think* was a 85L53. Finally, just to be confusing, the Brits decided that they would designate their guns by the weight of the projectile it fired. Never mind that AP and HE weigh different amounts, but there you go. So instead of the Brits having a 76mm gun, they call it a 17lber. I think the 2lber is 40mm, the 6lber 57mm, the 17lber 76/77mm, and the 25lber ~90mm. Jeff Heidman Link to comment Share on other sites More sharing options...
Guest Pillar Posted July 12, 2000 Share Posted July 12, 2000 Ok, thanks for the help. Link to comment Share on other sites More sharing options...
Redleg Posted July 12, 2000 Share Posted July 12, 2000 Acually the poundage of the british guns refers to the weight of a lead sphere that would fit into a particular barrel. So the 17lb gun would fit a 17lb lead ball in the tube. The round itself was probably heavier than 17lb. Still a confusing system, darned brits. Link to comment Share on other sites More sharing options...
Holman Posted July 12, 2000 Share Posted July 12, 2000 Unless I'm misremembering, I've noticed that BTS converts British "pounder" ratings to standard US/German millimeter ratings on the unit info screen that pops up when you hit Enter. This makes it easier to judge just how big those Limey weapons are. Link to comment Share on other sites More sharing options...
tss Posted July 12, 2000 Share Posted July 12, 2000 Jeff Heidman wrote: Generally, the longer the barrel, the higher the velocity of the round. This is true up to some point. The shot gets its energy from expanding gasses of ignited propellant. If the barrel is too short some of this energy is wasted when the gasses spread out to all directions from the muzzle. If the gun barrel is of the optimal lenght, at the gunpoint the force provided by the gasses is exactly as great as the air resistance that slows the round. If the barrel is longer than that, the round starts to slow down in the barrel. I'm not certain where the cutoff point is regarding to modern guns. In the era of black powder weapons guns were usually too long. The most extreme example is the "Queen's Pocket Pistol" that was designed to fire over the English Channel. Its barrel lenght was somewhere near 10 m. Instead of France, the test shot landed only 1000 meters away. The same range could have been achieved with a 2 meter barrel... - Tommi Link to comment Share on other sites More sharing options...
IntelWeenie Posted July 12, 2000 Share Posted July 12, 2000 The Brit 25 pounder was 88mm (hmmm!). A longer barrel is a good rule of thumb to follow for AP effectiveness. One of the main reasons for having the longer barrel, though, is so that the powder charge used could be larger, increasing velocity. Otherwise, the extra powder would burn past the muzzle where it is not nearly as effective. (but cool looking) This could be taken to an extreme, especially with some AT guns that the Germans tried that used a tapered bore. The theory was that a large powder charge pushed a smaller than normal projectile (fitted with skirts to match bore size) at VERY high velocity. Problem they ran into was that steel shells tended to fragment rather than penetrate at these velocities, and they didn't have enough tungsten to make them wothwhile. ------------------ "Belly to belly and everything's better" - Russian proverb Link to comment Share on other sites More sharing options...
Wittmann Posted July 12, 2000 Share Posted July 12, 2000 Taper bore refers to the shot fired being squeezed as it travels up the barrel. Since the propellant force is acting over a reducing diameter, the velocity increases. I'm sure a math / physics major could sort out the equation...It's too long ago for me to remember :-0 [This message has been edited by Wittmann (edited 07-12-2000).] Link to comment Share on other sites More sharing options...
IntelWeenie Posted July 12, 2000 Share Posted July 12, 2000 Will the taper bore guns be included in CM2, 3, 4? I know the ones that got the most use were the little 28mm jobbies, but there were also 50mm and 75mm versions. Very effective, but too rare for CM's scope? (Hopefully not; the Pupchen was included, after all... ) ------------------ "Belly to belly and everything's better" - Russian proverb Link to comment Share on other sites More sharing options...
Guest Scott Clinton Posted July 12, 2000 Share Posted July 12, 2000 I would think that the taper bore weapons would have to be included in CM2 and esp. CM3. I would expect that they are not in CM1 because by mid '44 the supplies of tungsten in Germany's hands were VERY, VERY limited. I think it was exclusively restricted for use in the manufacture of machine tools for the arms industry by 1942 (with the exceptoin of the 28/20 that was being phased out at the time). ------------------ Please note: The above is solely the opinion of 'The Grumbling Grognard' and reflects no one else's views but his own. Link to comment Share on other sites More sharing options...
Guest Michael emrys Posted July 12, 2000 Share Posted July 12, 2000 <BLOCKQUOTE>quote:</font><HR>Originally posted by Wittmann: Since the propellant force is acting over a reducing diameter, the velocity increases.<HR></BLOCKQUOTE> This is not exactly so. The fact is, that for maximum acceleration, you want the largest area for the base of the projectile that is practical. On the other hand, for sustained velocity after the projectile leaves the barrel of the weapon, you want it to have the smallest frontal area as possible. The squeeze-bore gun was an attempt to reconcile these conflicting requirements. So the round starts off large, but leaves smaller. All it all, the British found a much better way to achieve the same goal by using the discarding sabot round. This entails neither the production difficulties of machining a tapered-bore barrel nor the friction losses as the round passes up it. Michael Link to comment Share on other sites More sharing options...
Guest Pillar Posted July 12, 2000 Share Posted July 12, 2000 What's a muzzle break for? Link to comment Share on other sites More sharing options...
IntelWeenie Posted July 12, 2000 Share Posted July 12, 2000 <BLOCKQUOTE>quote:</font><HR>Originally posted by Pillar: What's a muzzle break for?<HR></BLOCKQUOTE> It reduces the recoil force of the gun by venting some of the gases to the sides. It sometimes is designed to also reduce the muzzle flash (at least on smaller guns; this is not really practical on arty pieces). ------------------ "Belly to belly and everything's better" - Russian proverb Link to comment Share on other sites More sharing options...
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