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Subject: Gun Caliber
technoid    7/20/2004 9:48:12 AM
Here's another question that probably shows my ignorance in the subject of large guns but I noticed in looking at web sites for large cannons that the term "caliber" is used differently for large guns. In the realm of small arms "caliber" is the bullet or bore size. When talking large guns it appears the term "caliber" refers to barrel length. Why is this different and how did it come about? In small arms the barrel length is simply refered to in units of length like "inches".
 
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scholar    RE:Gun Caliber   7/20/2004 3:06:45 PM
I think you're wrong about this. Calibre is calibre. On the other hand, I'm at least as ignorant as you, so hopefully one of the gunners will chime in.
 
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IsoT    RE:Gun Caliber   7/20/2004 5:11:12 PM
Well calibers in big guns measn how many caliber lenghts the tube is. (tube is the barrel of gun) Roughly, longer the tube, higher muzzle velocity. (well, upto some point.) well the tank gun is say 44 cals long menas the tube is 120mmx44=5280mm so 120mm gunbarrel is bit over 5 metres long (5 metres 28 centimetres).
 
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scholar    RE:Gun Caliber   7/20/2004 5:21:04 PM
MEaning how many times the calibre of the shell?
 
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Steve    RE:Gun Caliber   7/21/2004 12:55:48 PM
The above is correct and there is no reason not to give the barrel length of small arms in multiples or bore diameter (caliber), it?s just not common. There is another confusing nomenclature out there I saw questioned in another post. You frequently see a weapon designated as 40L70 ie. 40mm bore with a barrel 70x40mm (2.8m) long. The confusion comes from the brits who use L to designate Land, the much the same way the US uses M or the Canadians C. So the Challenger 1?s gun was the L11 and the Chally2?s the L30 but both were on the order of 120L40to50.
 
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scholar    RE:Gun Caliber   7/21/2004 1:22:24 PM
I miss the old days when one spoke of ammo weight. Six-pounders, etc.
 
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doggtag    RE:Gun Caliber and ammo weight   7/21/2004 10:26:22 PM
yes, but... there again is a problem: majority of 155mm guns fire "nominally" sized projectiles about 50kg. But when you look at just how many varied shells there are for each gun diameter, saying a gun fires a 35pound shell doesn't really tell you if its a 120mm tungsten sabot round (as opposed to a 40-odd pound DU round), or a 105mm artillery gun HE round. In WW2, there was the British 2pdr AT gun (of 40mm bore diameter). But the DU shells for the A-10's GAU-8 (of 30mm bore diameter) each weigh about 2 lbs also. Measuring guns by the weight of shell they threw met a dead-end when everyone found out just what kind and weight of "stuff" can be packed into "shells", as opposed to the old solid shot that was the determining factor of the "poundage" of a gun..
 
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technoid    RE:Gun Caliber and ammo weight   7/28/2004 12:17:31 PM
So back to my original question. What came first, the small arms terminology where "caliber" means bore size, or the large gun terminology where "caliber" means barrel length? And why do the two schools differ in the meaning? And where does he distinction change, when you get up to anything bigger than a 50 caliber bullet do we start using the term differently? I'm just curious and always want to learn.
 
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IsoT    RE:Gun Caliber and ammo weight   8/6/2004 4:08:32 PM
Weren't the ammo weight thing the same as with shotgus still today. Meaning 12 bore shotgun means the bore is the size of lead speher of which 12 goes for pound. Hence twopounder would meant it takes two that size speher for a pound. Made sence when your artillery round was a sphere, but now as the rounds might be even five times the bore diameter isn't really informative. And dont even start from the shotsize. Havent got a clue how they go.
 
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wagner95696    RE:Gun Caliber and ammo weight   8/7/2004 3:18:53 PM
Caliber means bore size. Barrel length is correctly expressed as 'calibers', plural. For example, L/55 means the barrel is 55 calibers long, or 55 times the caliber. Caliber [bore size, e.g. 155mm] is an actual measurement wheras 'calibers', plural is a ratio [55:1] and independent of any specific measurement. The problem is that over the years people got sloppy with their grammar and dropped the 's' from 'calibers', thus causing the confusion.
 
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technoid    RE:Gun Caliber and ammo weight   8/11/2004 4:45:12 PM
A friend just suggested that perhaps the term "caliber" denoting bore size is a U.S. or English term. Perhaps the term "calibers" denoting tube length is a French term. Many gun terms originated in French. Anyone know if there is a French term that might be translated "calibers" and what it means?
 
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k3n-54n    RE:Gun Caliber and ammo weight   8/14/2004 4:24:52 PM
IsoT, a four pounder is bigger than a two pounder. I don't think they were based on lead spheres, but, even if they were, the measurement is basically the inverse of guage. One of the fun things about ammunition is the variety of ways in which it is described. While anyone with any sense must find it appalling and chaotic, I say that is the charm.
 
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french stratege    RE:Gun Caliber and ammo weight   8/14/2004 9:20:38 PM
Calibers is not tube lenght but diameter.It translate from the French term "calibre" which mean the diameter of an hole.If we say 50 time calibers to exprimate the lenght of a gun it is because it shows immediately potential performance as a piston pressure ratio in a explosive engine of a car.
 
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technoid    RE:Gun Caliber and ammo weight   8/18/2004 4:38:38 PM
I think I've finally figured this out and it's not nearly as complicated as I wanted it to be. Based upon the discussion and the reponse from the kind Frenchmen I have drawn a reasonable conclusion how the terminology confusion came about. If the bore diameter is from the French work "calibre" I would conclude that the term caliber as applies to tube length was just a convention developed to express the length as a function of bore size. I would guess that as "french stratege" has implied that folks simply began to shorten the terminology and rather than talk about a barrel being 38 calibers long they simply began calling it a 38 caliber tube. There is probably no more explanation than that. Well, for what's it worth I learned something, thanks for all the discussion.
 
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neutralizer    RE:Gun Caliber and ammo weight   8/26/2004 5:09:57 AM
For artillery calibre is always measured between the surface of the lands in the bore. The shell is different, the dimaeter of the body is slightly less than the calibre and the diameter of the driving band is rather more. Correctly 'calibre length' is one way of definging barrel length in terms of the barrel's calibre. Sloppy users who perhaps don't really know what they're talking about have got into a habit of talking about 'calibre' when they actually means 'calibre length' in relation to the barrel's length. It seems to be a fairly modern practice (well after WW2)in widespread use. The problem is there isn't any agreement on what's being measured and what it means. Barrels have several lengths, about the only thing that seems commonly agreed is that barrel length excludes any muzzle brake. Barrel length could be the length of rifling, the length from breech face to muzzle face, muzzle face to the rear face of the barrel when the breech assembly is removed, or perhaps even to the rear face of the breach assembly. Historically, many European armies gave names to different size cannons (culverin, etc). It's also quite reasonable to give a standard weight for a modern gun's shell it is merely 'the shell weight for which the firing table is compiled'. The Brits only designated 'guns' by weight, 'howitzers' were designated by calibre. However, for real confusion over calibre you have to turn to small arms, eg the UK's latest 'long range rifle', it fires an ammo usually given in inches in the US, MoD give the weapon a metric calibre, try converting the inches to mm or vice versa! I guess this is one for another thread, but I suspect NATO has an agreed method of measuring small arms calibre but ammo manufacturers don't use it.
 
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fatarian       10/13/2007 7:24:45 AM
In my country , they alway describe the howitzer as 155mm 52 caliber...while i understand (  correct me if my understanding is wrong) that 155mm means the diameter of barrel, by 155mm x 52 caliber = 8060mm barrel length..i still don understand why 52 calibre. How do i undestand the term 155mm 52 calibre..........does 52 calibre means there is 52 rifling in the barrel........if 52 calibre means the diameter of the bore, then what does 155mm means...? Thanks
 
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