ammo diameter, not strictly SPWAW related

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ammo diameter, not strictly SPWAW related - 3/26/2004 3:49:59 AM

minefield

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How did they settle on the diameter of bullets and artillery rounds? I see things like 7.62 mm (I see now that's 3 * conversion factor 2.54 (English to metric) * some power of 10), 7.92 mm, 37mm, 81mm, 88mm, 105mm, etc. Are these arbitrary? Are they some fraction of an inch? And why would they use a diameter based on English/standard then convert back to metric?
Err, I just don't see any pattern or logic in it.

Also, where do the British rounds rated in pounds come into this. How does a 17pdr or 20pdr shell compare to metric / standard ammo?

< Message edited by minefield -- 3/25/2004 8:52:12 PM >

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RE: ammo diameter, not strictly SPWAW related - 3/26/2004 12:30:12 PM

Belisarius

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I have no idea as to where and when these became 'standards', but the origin must have been an inch-based standard.

.223= 5.56mm
.30 = 7.62mm
.354= 9mm
.50 = 12.5mm

3"= 76.2mm

and so on.

The British 'pound' designation of guns is referring to the grenade weight. I know the Navy were early to use this but I don't know if the army picked it up or it came to be at the same time. The latter makes more sense. AmmoSgt?

I had an EXCELLENT page on this but unfortunately Google only turns up modelling sites.

Quick out of my head:

3pdr = 47mm
6pdr = 59.6mm

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RE: ammo diameter, not strictly SPWAW related - 3/26/2004 3:38:05 PM

minefield

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Thanks alot. This is exactly what I wanted to know. Any idea about the larger pounder ammo's diameter? Maybe we can get AmmoSgt to tell us how these sizes were fixed (the standard / English sizes i.e. .354). I can't see that such numbers are common fractions.
I have wondered about standardization even with small arms. It seems it just arbitrarily goes from .22, 6mm, .25, 6.5mm, .30, etc on up.

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RE: ammo diameter, not strictly SPWAW related - 3/26/2004 4:13:10 PM

Voriax

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Another thing...there has been lots of different inches. For example just about every German state had its own inch during the black powder age..I have some cannon blueprints that use 'Vienna inch', for example. So 7,92 might easily be 3/10 of some German inch. And when armies transitioned from balck powder guns to smokeless powder calibers tended to decrease. So if you had a some nice calibre that was fractions/multiplies of an inch and you take 15% out of it then it is kinda hard to 'fit it in'. Then consider companies that are competing for a large government order...many cases they each had own cartridge that was of course different than competitor's cartridge.

Voriax

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RE: ammo diameter, not strictly SPWAW related - 3/27/2004 3:11:22 AM

Hades Strikes Back

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I thought 50 cal was 12.7

I know 2lber is 40mm and 25lber is 88mm
and I thought the American 57mm was based on the British 6lber. Wouldn't that make the 6lber 57mm? Or did they change the shell size to fit a 57mm barrle?

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RE: ammo diameter, not strictly SPWAW related - 3/27/2004 9:11:50 AM

Belisarius

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quote:

ORIGINAL: Hades Strikes Back

I thought 50 cal was 12.7

I know 2lber is 40mm and 25lber is 88mm
and I thought the American 57mm was based on the British 6lber. Wouldn't that make the 6lber 57mm? Or did they change the shell size to fit a 57mm barrle?

Do you have solid info on the 25lber? I thought it was slightly less, 85mm.

Wasn't there a 6 pdr qwf gun? That may explain the 57mm, but then again since I pulled this out of my head, you may well be more correct than me.

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RE: ammo diameter, not strictly SPWAW related - 3/28/2004 1:46:12 AM

Hades Strikes Back

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no solid info but i remember playing a scenario with a bunch of 25lber SPAs and in the info it said that 25=88 and I thought to myself too bad they dont shoot like 88s. And it just stuck with me that they were 88mm. But i might be wrong.

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RE: ammo diameter, not strictly SPWAW related - 3/29/2004 2:21:46 AM

Major Destruction

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2 pounder (write 2 Pdr not 2lber) = 1.575 inches or 40mm
6 pounder = 2.24 inches or 57mm
17 pounder = 3 inches or 76.2mm
77mm OQF = 3 inches or 76.2mm
3.7in OQF = 3.7 inches or 95mm (weight of shot = 10.5 pounds)
95mm OQF = 3.7 inches or 95mm (weight of shot = 25 pounds
OQF 25 pounder = 3.46 inches or 88mm (weight of shot 25 pounds)
OQF 32 pounder = 3.67 inches or 93.4mm

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RE: ammo diameter, not strictly SPWAW related - 3/29/2004 11:41:58 PM

Hades Strikes Back

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cool thanks for the info
sorry about lber :P

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RE: ammo diameter, not strictly SPWAW related - 3/30/2004 6:06:54 AM

minefield

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Thanks all.

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RE: ammo diameter, not strictly SPWAW related - 3/30/2004 11:43:37 PM

mattenhoff

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Wasn't there a 20 pdr as well? In Centurion Tank. I recall it was 84mm in diameter, and had a fairly good punch. First seen in action in the Korean war.

Is this correct?

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RE: ammo diameter, not strictly SPWAW related - 4/9/2004 1:08:57 AM

arethusa

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A little bit more info for this topic.

As somebody else said, much of this probably goes back to black powder days when the size of the gun was given as the weight of solid shot it fired. A rail-mounted swivel gun could be a 1- or 2pdr. Most field guns were 4 pdr and some were 8pdr. Guns in forts and on board ships were typically 12-, 18 and 24pdr but the big Line-of-Battle-Ships (where the name battleship comes from) usually carried 32pdr on the lowest deck and sometimes even as big as 42pdrs.

I stood 200 yards in front of and off to the side of a 42pdr firing once and the noise was incredible. Even doing the standard artillery pose of mouth open and hands over ears it deafened me for a few minutes. From alongside it or inside the confines of a ship's deck it defies beleif what it would have been like. And this from an old artilleryman! 105mm's were never that bad. I know in black powder days ship's gunners wrapped their bandanas around their ears to muffle the sound but even then, bleeding from burst eardrums from their own guns was common with the larger sizes.

The weight of a shell would differ for the same gun depending on the type of ammo being fired. The standard shell shell for a 105mm was around 30 lbs but armour piercing was heavier and starshell was lighter. There was also shrapnel, fused, flare and smoke shells of various types and each had a different weight. So a 25pdr did not necessarily fire a 25 lb shell.

The reason a 25pdr didn't have the hitting power of an 88mm was mostly because of muzzle velocity and type of shell fired. 25pdr's were made to fire HE over long distances in an arced trajectory while 88mm's were made to fire AP over long distances in a flat trajectory. The difference isn't just the type of ammo but also the speed it travels. If you look at a 25pdr, the barrel is relatively short. I don't know for sure but I'd guess maybe 8-10 feet long and straight. The barrel of an 88mm might be twice as long and tapered. This causes two things to happen. If the length of the barrrel is increased, the explosive power remains in contact with the shell for a longer period of time thus making it go faster. Like peddling a bycycle a few times and coasting or peddling it a lot of times before coasting. The taper of the barrel also makes it go faster by squeezing the shell and making a tighter fit so less explosive gas escapes and the shell has to go faster to get out of the barrel. Finally, the cartridge part (the brass part that stays behind in the gun) had more explosive in the 88mm than in the 25pdr. In a 25pdr, the cartridge is the same diameter as the warhead but in some ATG's, the cartridge was considerably bigger than the warhead, just like a .22cal the brass part is the same dia. as the bullet but in a .303 it's about 1/3 again as big.

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RE: ammo diameter, not strictly SPWAW related - 4/15/2004 7:19:28 PM

o4r

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Depend on which version of 25 pdr you are referring, their acutal calibre is 87.6mm (3.45 inch)

1 pound = 1 lb

OQF (Ordnance, Quick Firing) 25 pdr (pounder) gun MK1
Generally known as 18/25 pdr, weapn limited in elevation to 30 deg, called so as it retent the 18 pdr MK IIITP carriage.
It weigh 3570lb, on mounting traverse angle of -5 to 37 deg. 4.5 left and right. range of 12000 yds with a 25lb shell fired from the L/28.13 barrel (28.13 * 87.6 mm) muzzle velocity is 520 m/sec.
Converted from 18 pdr by boring the barrel to larger dia of 87.6 mm to fire 25 pdr shell.

OQF 25 pdr gun MK 2
Weigh 3868 lbs
on mounting elevation of -5 to 40 deg, 4 deg left or right.
Range 13400 yds (12,255 m) with a 25 lbs (11,34 kg) shell
Barrel length is L.28.25
In service 1940

OQF 6 pdr (delivered in Sept 1941 after a design and development process that started in 1938)
Calibre is 57mm
MkI - used for training
MkII - L/42.8
MKIII - unknown
MKIV - L/45
fire a 6.28 lb (2.85 kg) Standard shot or normal AP round to 823m/s to penetrate 69mm at 20 deg armour at 1000 yds.

88 L56 meant that the barrel is 88mm * 56 and 88 L71 is 88mm * 71. note the huge different in barrel length.

hope that help

< Message edited by o4r -- 4/16/2004 1:19:16 AM >

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RE: ammo diameter, not strictly SPWAW related - 4/15/2004 8:31:44 PM

Belisarius

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quote:

ORIGINAL: arethusa

A little bit more info for this topic.

As somebody else said, much of this probably goes back to black powder days when the size of the gun was given as the weight of solid shot it fired. A rail-mounted swivel gun could be a 1- or 2pdr. Most field guns were 4 pdr and some were 8pdr. Guns in forts and on board ships were typically 12-, 18 and 24pdr but the big Line-of-Battle-Ships (where the name battleship comes from) usually carried 32pdr on the lowest deck and sometimes even as big as 42pdrs.

I stood 200 yards in front of and off to the side of a 42pdr firing once and the noise was incredible. Even doing the standard artillery pose of mouth open and hands over ears it deafened me for a few minutes. From alongside it or inside the confines of a ship's deck it defies beleif what it would have been like. And this from an old artilleryman! 105mm's were never that bad. I know in black powder days ship's gunners wrapped their bandanas around their ears to muffle the sound but even then, bleeding from burst eardrums from their own guns was common with the larger sizes.

Don't forget the 64pdr carronades, usually mounted one on each side on the poop deck. Nicknamed "the devil's gun" by the French and "smasher" by the British, IIRC. The Royal Navy used this device from c:a 1760, it'd be a lot longer before the French came up with a similar construction.

Imagine the hellish chaos when to ships were locked in close combat and one of those fired over the enemy top deck.

< Message edited by Belisarius -- 4/15/2004 7:27:51 PM >

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RE: ammo diameter, not strictly SPWAW related - 4/16/2004 6:39:50 AM

arethusa

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Yes, I should have mentioned carronades. They came in sizes of 18, 24 and 32 pdr as well. USS Constitution carried 24's for instance IIRC, or maybe they were 18's and just her long guns were 24's. However, carronades are sort of in a class by themselves. Almost like a cross between a mortar and a big shotgun. They had tremendous power but a very short range because of the short barrel. When in range, a carronade could go through almost anything the navies had at the time or if using cannister or grapeshot, they could clear a whole deck.

Perhaps on Swedish ships they were mounted in the stern or on the poop deck, but in British ships they were normally on the for'c's'l. Some British ships (Glatton for instance at the Battle of Copenhagen under Capt. Bligh - yes THAT Capt. Bligh) had carronades for all their guns. Others, like Constitution, only had carronades on the spar deck and these weren't even counted when they rated the ship. Thus, Constitution rated as a 40 gun but in fact, had up to 55 guns if you got close enough for her to use all of them.

BTW, if you ever get to Boston on July 4th, make it a point to see Constitution's annual turn-around cruise. She exchanges a 21 gun salute with a fort at the outer harbour. Really something to see all the smoke and booms of the big guns going off.

Victory at Portsmouth has a pair of 64 pdr carronades at her bow and is the best example I know of anywhere what those SOL's were like. You can see HMS Warrior there too which is from the transition period between sail and steam and wood and iron and muzzle- and breech-loading.

There are a few other men-o'-war around the world too, like Constellation or Trincomalee but Victory and Constitution are something special.

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