# Interesting question about Calibre of Artillery Pieces.



## George Wallace (23 Jul 2008)

I was just on this Armada site ( http://www.armada.ch/03-4/complete_03-4.pdf ) and have come across something I am not familiar with.  There are stats on numerous Guns and there are several different calibres for 155mm Guns.  For instance, the M109A6 Palladin is 39 calibres, the 2S5 Giatsint-S is 49 Calibres, and the AS 90 and PzH 2000 are 52 Calibres, while the Giat GCT is 40 calibres.  

I am totally unfamiliar with this measurement.


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## Michael OLeary (23 Jul 2008)

I could be wrong, but I believe it refers to barrel length 'calibre units'.


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## George Wallace (23 Jul 2008)

I was debating that, or barrel thickness.


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## 421 EME (23 Jul 2008)

George

 I will confirm this this tomorrow, but what I can remember from my QL5 Weapons Tech course is that calibre in the Arty world is the length of the barrel measured by the diameter of the projectile it fires. So for the PzH 2000 it has a 155mm/52 calibre barrel this means the barrel length in metric is 8060mm. Why they do it this way, I could not tell you.


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## muskrat89 (23 Jul 2008)

Yes, it is barrel length

Edit to add - 421 EME nailed it


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## George Wallace (23 Jul 2008)

Thanks guys.  I guess, for most of us that would be considered UFI; if not just outright confusing.


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## McG (24 Jul 2008)

The same measure applies to the length of tank barrels.  It seems that "calibers" is typically left unstated and so you see "L44" and "L55" for the Rheinmetall 120 mm gun.


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## TangoTwoBravo (24 Jul 2008)

It is confusing, but the use of the "Lxx" calibre measurement allows people to differeniate between shells of the same diameter but that are very different in their characteristics.  The Germans, for instance, had a dizzying number of 75mm weapons out there which varied widely in their characteristics, ranging from the low-velocity short barrelled L24 on the first MkIVs to the longer L43 and L48 on later Mark IVs which had much greater anti-tank capabilities and then the very powerful L70 on the Panther (this is just the 75mm guns on tanks, they had others).  Just saying "long 75" wouldn't cut it when there were many different "long 75s."   

Battleships used the same measurements (not all 16 inch battleship guns are created equal).


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## OldSolduer (24 Jul 2008)

Now I get it.

Dr. Gerald Bull developed the Gun Cal 45. It evolved into an artillery piece that the South Africans used when there was a weapons embargo placed on them. Bull, a Canadian citzen, considered a genius, was jailed in the US for that. This arty piece was state of the art. It apparently could out gun the best the USA had to offer, but the US and NATO rejected it in favor of the M109 and its 155 mm gun. 
Bull had a project that saw him launch payloads into space using artillery pieces. I think it was called HARP, or the High Altitude Research Project.

Dr. Bull was assassinated in Europe....can't remember which city. Some say the Israelis did it, others say the Iraqis. He was apparently working on a Supergun for Sadaam Hussein.

An interesting individual.


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## Colin Parkinson (26 Jul 2008)

Tango2Bravo said:
			
		

> It is confusing, but the use of the "Lxx" calibre measurement allows people to differeniate between shells of the same diameter but that are very different in their characteristics.  The Germans, for instance, had a dizzying number of 75mm weapons out there which varied widely in their characteristics, ranging from the low-velocity short barrelled L24 on the first MkIVs to the longer L43 and L48 on later Mark IVs which had much greater anti-tank capabilities and then the very powerful L70 on the Panther (this is just the 75mm guns on tanks, they had others).  Just saying "long 75" wouldn't cut it when there were many different "long 75s."
> 
> Battleships used the same measurements (not all 16 inch battleship guns are created equal).



the Soviets solved this by renaming different guns by 1mm out, so 122mm gun might be called the 123mm, this insured the correct ammo was sent to the right gun. The 106mmRR is the same, the round is 105mm.


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## McG (30 Jul 2008)

Colin P said:
			
		

> the Soviets solved this by renaming different guns by 1mm out, so 122mm gun might be called the 123mm, this insured the correct ammo was sent to the right gun. The 106mmRR is the same, the round is 105mm.


I seem to recall the west has done the same thing a few times.  I seem to recall that the 106 mm recoilless was in fact a 105 mm but renamed to avoid confusion with existing ammo, and the 77 mm tank cannon on the A34 Comet was in fact 75 mm HV but renamed to avoid confusion with existing 75 mm, 76 mm and 17 pounder ammunition. 



			
				Tango2Bravo said:
			
		

> It is confusing, but the use of the "Lxx" calibre measurement allows people to differeniate between shells of the same diameter but that are very different in their characteristics.  The Germans, for instance, had a dizzying number of 75mm weapons out there which varied widely in their characteristics, ranging from the low-velocity short barrelled L24 on the first MkIVs to the longer L43 and L48 on later Mark IVs which had much greater anti-tank capabilities and then the very powerful L70 on the Panther (this is just the 75mm guns on tanks, they had others).


Did the different cannons fire different ammunitions?  The barrel length in calibers was a feature of the weapon and not so much the ammunition and there would normally be another designation to differentiate between ammunition (overall length, casing length, "high velocity/pressure", or false diameter).  In theory, a 120 mm L44 will fire the same ammunition as a 120 mm L55 ... but the new US SABOT has much higher peak pressures that exceed the safe threshold other nations have rated for their barrels (L44 and L55).


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## TangoTwoBravo (30 Jul 2008)

MCG said:
			
		

> Did the different cannons fire different ammunitions?  The barrel length in calibers was a feature of the weapon and not so much the ammunition and there would normally be another designation to differentiate between ammunition (overall length, casing length, "high velocity/pressure", or false diameter).  In theory, a 120 mm L44 will fire the same ammunition as a 120 mm L55 ... but the new US SABOT has much higher peak pressures that exceed the safe threshold other nations have rated for their barrels (L44 and L55).



The 75mm L24, the 75mm L43/L48 and the 75mm L70 tank guns fired different ammunition.  

The 75mm L24 was intended to provide fire support with HE while the MkIIIs with 37mm and 50mm higher-velocity cannons dealt with enemy tanks.  The 75mm L24 was found primarily on the early MkIV up to and including the F1 variant.  The L43/L48 were longer guns and fired a bigger round (both the casing and the projectile) and it was brought in to try to deal with the T34s and KV1s (circa 1942).  The L43 was found on the MkIVF2 and the MkIVG.  This was the tank gun that gave the British fits in the Western Desert when it arrived (the MkIV "Special").  The L48 was found on the MkIVH circa 1943 to 1945 (and some of the later Gs I believe).  I think that the L43 and L48 guns fired the same ammunition, but I believe that the L48 had better performance due to the longer barrel.  I imagine that the breech and recoil system for the L43/48 was much different than that found on the L24 (they could fit the 75mm L24 in the MkIIIN but not the 75mm L43).  The 75mm L70 round for the Panther is bigger again than the L43/L48.  The two 88mm tank guns (L56 found on the early Tigers and the later L71) fired different ammunition as well.  As an aside, the 75mm L70 actually had better AT performance than the 88mm L56. - Please note that I have left out the myriad of Stugs and Tank Destroyers which employed these guns and others.

This site has some pictures.

http://www.hypospace.net/equipment/Ammunition%20Gallery.htm

I don't know if the Lxx designation helped ammo guys, but I imagine that it would have helped planners and staffs.  They might have had serial numbers in any case to differentiate between ammunition.  Any WWII German Ammo Techs on the board?

Cheers


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## Cdn Blackshirt (30 Jul 2008)

George Wallace said:
			
		

> I was just on this Armada site ( http://www.armada.ch/03-4/complete_03-4.pdf ) and have come across something I am not familiar with.  There are stats on numerous Guns and there are several different calibres for 155mm Guns.  For instance, the M109A6 Palladin is 39 calibres, the 2S5 Giatsint-S is 49 Calibres, and the AS 90 and PzH 2000 are 52 Calibres, while the Giat GCT is 40 calibres.
> 
> I am totally unfamiliar with this measurement.



I could be mistaken but I believe the caliber measurement you mentioned is actually a relational measurement of barrel length vs barrel diameter....so a 52 caliber 105mm gun would be 5460mm (105mm x 52) while a 52 calibre 155mm gun would be 8060mm (155mm x 52).

If an artillery specialist corrects me, I'll gracefully defer to them...but I'm pretty sure that's how it works.


Matthew.


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## TangoTwoBravo (30 Jul 2008)

Cdn Blackshirt said:
			
		

> I could be mistaken but I believe the caliber measurement you mentioned is actually a relational measurement of barrel length vs barrel diameter....so a 52 caliber 105mm gun would be 5460mm (105mm x 52) while a 52 calibre 155mm gun would be 8060mm (155mm x 52).
> 
> If an artillery specialist corrects me, I'll gracefully defer to them...but I'm pretty sure that's how it works.
> 
> ...



Read 421 EME's post on this thread.


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## Cdn Blackshirt (30 Jul 2008)

Tango2Bravo said:
			
		

> Read 421 EME's post on this thread.



That'll teach me to skim....


M.   :


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## vonGarvin (30 Jul 2008)

Cdn Blackshirt said:
			
		

> If an *artillery * specialist corrects me, I'll gracefully defer to them...but I'm pretty sure that's how it works.


T22B got to you first, and he's not even artillery.  ;D

Interesting side note, any wargamer who played Squad Leader to the Cross of Iron level (the first expansion to it) would be very familiar with the "L" system for calibres.  
The Tiger (Panzer VI E) had an 88L (in game terms), the Panther (Panzer V) had a 75LL and the Bengal tiger ("Königstiger", or Panzer VI B) had an 88LL.
The raw kill power, vs frontal armour, was 8, 9 and 11 respectively (eg: you had to roll that number or less on two 6 sided dice).  Now, the various tanks each had their own armour modifiers, but the real difference was in accuracy.  A weapon with "L" as a modifier was more accurate at longer ranges than those without the "L", and the "LL" weapons were even more so accurate.  So, a Panther had a better chance to hit its target, at longer ranges, than a Tiger (Mk VI E), all things being equal.

Anyway, geek mode off....


EDIT: and on again.
I think the big difference that calibres can make can be found in the evolution of the T 34 (at least in Cross of Iron terms).
The T 34 A had, in game terms, a 76
The T 43 B had, in game terms, a 76L
The T 43 C was improved in its protection only.
The T 43/85 had, in game terms, a 85L
The 75 had a "to kill" of 6, the 75L a "to kill" of 7 and the 85L a "to kill" of 8
One digit may not sound like much, but consider the chances of rolling each on a pair of six sided dice.

You have a 41.667% chance to roll 6 or less.
You have a 58.333% chance to roll 7 or less.
You have a 72.222% chance to roll 8 or less. 
So, going form 6 to 7 increases your chance to kill your target by almost 17%.  Nothing to sneeze at.


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## NavyShooter (30 Jul 2008)

Someone alluded to the application to Naval guns, but it is a nearly universal description.

EG, the 3"50cal gun found on the Fraser had a shorter barrel than the 3"70 gun on the Gatineau.  

The difference in barrel length is 50-70 (or 20) time the 3" diameter of the barrel, so 60", or 5 feet shorter for the 3"50.

NS


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## TangoTwoBravo (30 Jul 2008)

MR,

Just to add to our geekiness...

My comparing the 75mm L24 with the 75mm L43/L48 and 75mm L70 can be deceiving because more than just the barrel length was changing (different breeches and different ammo).  Armour penetration stats should be taken with a grain of salt, but I have seen charts that give the L48 about 15mm more armour penetration than the L43 with the same ammunition at the same range.  I assume that this added penetration is from a higher muzzle velocity resulting from the propellant gasses having more time to exert pressure on the projectile (caveat - I am a poli sci guy and not an engineer).  I imagine that there are diminishing marginal returns with extra length at some point - but an engineer can jump in any time.

Another example can be found with the Panther.  I have read that the first prototypes had a 75mm L60 gun, but this was found to be a little lacking during tests so they went with an L70 length barrel to improve performance.

Cheers


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## Colin Parkinson (30 Jul 2008)

Longer barrels, higher MV means more barrel droop and wear. A lot of issues with tank gun where not sorted out til after the war, thermal sleeves, fume extrators APDS issues etc.


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## LordOsborne (5 Sep 2008)

Tango2Bravo said:
			
		

> MR,
> 
> Just to add to our geekiness...
> 
> ...



I also understand that in addition to the longer lengths, new AP ammunition was being introduced throughout WW2 to make better use of the higher MV as well as advances in ballistic science. 
The basic AP shell gave way to the APC (Armour Piercing, Capped) which, if I recall, had a cap on the nose made of a softer grade of steel, which improved performance against some types of hardened armour plate by softening the shock of impact. Then came APCBC (AP Capped, Ballistic Capped) which was essentially the same APC round, only with a more aerodynamic nose cone, giving a better flight profile to the round.
Following that was APCR, (AP Composition Rigide) which had a hardened slug, sometimes tungsten carbide, inside a full-bore projectile made of a lighter metal such as aluminum. This was the stepping stone to APDS (AP Discarding Sabot), which, if I remember my Hist 245 class, was a British innovation to help improve their 17pdr AT gun. As better gun barrels were produced, the MV went up, and the performance of these new AP rounds improved as well.


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## Petard (6 Sep 2008)

Hmm, getting back the artillery aspect of the subject...

The longer the barrel the more accurate the gun tends to be, but at short range, for indirect fire purposes, this round tends to come in more shallow than say a shorter barrel (of the same bore diameter) firing at the same range, and therefore at short range the fragmentation warhead delivered by the longer barrel tends to be less effective. This because the round coming in shallow tends to have a fragmentation pattern shaped like a butterfly, whereas the round coming in more steep tends to have a more circular pattern.
Which is why the 39 cal barrel is still around. This is also what makes mortars so deadly.
Technology is trying to overcome the range shortcoming of the 39 cal barrel with things like Excalibur, course correcting fuses on things like rocket assisted and base bleed projectiles, or rounds like this:
http://www.janes.com/extracts/extract/jah/jah_5165.html
that are optimized for long range engagements, but not short range ones.

Then again looking at the people that responded to this thread I might very well be preaching to the choir


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