Convert pounders to mm for guns

[woods]

I always get confused above the above.

Read the following on the web :

I quote "There's no fixed forumla relating diameter to designation. The name - 20 pdr, 17 pdr, 6 pdr, etc, refers to the weight of the ammunition (just the shell I believe, not the complete cartridge). The weight will vary with both the diameter and legnth of the ammunition, so it's not as simple as you would hope.



That said, cannons tended to settle on standard sizes, and the pdrs were just the British versions of those. They were roughly equivalent to other nations' cannons of the same size. The common tank guns were



2 pdr: 40 mm

3 pdr: 47 mm

6 pdr: 57 mm

17 pdr: 76 mm



The 20 pdr was a post-war 84 mm tank cannon.

The 25 pdr was a field gun/howitzer, and was 88 mm

The 32 pdr was an anti-aircraft canon originally and was 96 mm".

The link :

http://forum.wotblitz.com/index.php?/to ... llimeters/

[BBfanboy]

ORIGINAL: woods

I always get confused above the above.

Read the following on the web :

I quote "There's no fixed forumla relating diameter to designation. The name - 20 pdr, 17 pdr, 6 pdr, etc, refers to the weight of the ammunition (just the shell I believe, not the complete cartridge). The weight will vary with both the diameter and legnth of the ammunition, so it's not as simple as you would hope.



That said, cannons tended to settle on standard sizes, and the pdrs were just the British versions of those. They were roughly equivalent to other nations' cannons of the same size. The common tank guns were



2 pdr: 40 mm

3 pdr: 47 mm

6 pdr: 57 mm

17 pdr: 76 mm



The 20 pdr was a post-war 84 mm tank cannon.

The 25 pdr was a field gun/howitzer, and was 88 mm

The 32 pdr was an anti-aircraft canon originally and was 96 mm".

The link :

http://forum.wotblitz.com/index.php?/to ... llimeters/

I always thought the 17 pounder was about 90mm - based on the mounting of the gun on the Sherman chassis to create a "Firefly" tank. I know it could pierce a Tiger's frontal armour at normal battle ranges. I may be confusing the 90mm figure with later tanks that carried that bore.

[Jorge_Stanbury]

Plus there is also the velocity of the projectile,

an early PzIV 7.5 cm KwK 37 L/24 short barrel, low velocity gun is not going to be the same as the long barrel/ high velocity 7.5 cm KwK 42 L/70 gun of a Panther

so you need to understand what kind of gun is that "xx" pounder you want to translate into mm

[woods]

Yes Jorge, I agree with you that the details are not that easy to convert. I was looking for the easy way out.

[JeffroK]

Its a British naming convention, probably goes back to Napoleonic era or earlier.
Like most things British it makes no sense[:'(]

[JeffroK]

ORIGINAL: Jorge_Stanbury

Plus there is also the velocity of the projectile,

an early PzIV 7.5 cm KwK 37 L/24 short barrel, low velocity gun is not going to be the same as the long barrel/ high velocity 7.5 cm KwK 42 L/70 gun of a Panther

so you need to understand what kind of gun is that "xx" pounder you want to translate into mm

As only the British named their weapons in this way they are very consistant. As they didnt talk metric I imagine it was easier than using inches. (By the way, it interesting that while the United States is rooted in imperial measurement, its Army has used metric terms for almost 100 years)

The following link goes to the website of Tony Williams, one of the experts in ammunition
http://www.quarryhs.co.uk/ammotables.htm

[woods]

Thanks JeffK for your link. Very informative. [&o]

[Reg]

ORIGINAL: JeffK

Its a British naming convention, probably goes back to Napoleonic era or earlier.
Like most things British it makes no sense[:'(]

Absolutely. It was the weight of a cannon ball...

[Reg]

ORIGINAL: JeffK

(By the way, it interesting that while the United States is rooted in imperial measurement, its Army has used metric terms for almost 100 years)

By coincidence I ran across this YouTube video today - The American Kilogram

Apparently the US signed the metre convention* and bases all customary units on SI standards. [X(]

* (also known as the Treaty of the Metre, is an international treaty that was signed in Paris on 20 May 1875).

P.S. The UK signed it too....

Who would have known. [:)]

[Chris21wen]

ORIGINAL: JeffK

Its a British naming convention, probably goes back to Napoleonic era or earlier.
Like most things British it makes no sense[:'(]

Try this
http://www.arc.id.au/Cannon.html

If it does not make sense to you good! That's how we like it confusion in the enemy ranks.[:D]

[wdolson]

ORIGINAL: BBfanboy

I always thought the 17 pounder was about 90mm - based on the mounting of the gun on the Sherman chassis to create a "Firefly" tank. I know it could pierce a Tiger's frontal armour at normal battle ranges. I may be confusing the 90mm figure with later tanks that carried that bore.

The 17 pounder was roughly equivalent to the 75mm on the Panther. It was a long barrel high velocity 75/76mm gun. The Super Sherman built after the war had a US 90mm and it required a larger turret to accommodate the gun. The turret of the standard Sherman could take a low velocity 105mm howitzer, but it could only take a high velocity gun of around 75mm.

Bill

[BBfanboy]

ORIGINAL: wdolson

ORIGINAL: BBfanboy

I always thought the 17 pounder was about 90mm - based on the mounting of the gun on the Sherman chassis to create a "Firefly" tank. I know it could pierce a Tiger's frontal armour at normal battle ranges. I may be confusing the 90mm figure with later tanks that carried that bore.

The 17 pounder was roughly equivalent to the 75mm on the Panther. It was a long barrel high velocity 75/76mm gun. The Super Sherman built after the war had a US 90mm and it required a larger turret to accommodate the gun. The turret of the standard Sherman could take a low velocity 105mm howitzer, but it could only take a high velocity gun of around 75mm.

Bill

Thanks Bill - that explains why I got 90mm stuck in my head for an up-gunned Sherman, while I also knew of the 17 pounder being used on the Firefly version.

[Ian R]

ORIGINAL: wdolson

ORIGINAL: BBfanboy

I always thought the 17 pounder was about 90mm - based on the mounting of the gun on the Sherman chassis to create a "Firefly" tank. I know it could pierce a Tiger's frontal armour at normal battle ranges. I may be confusing the 90mm figure with later tanks that carried that bore.

The 17 pounder was roughly equivalent to the 75mm on the Panther. It was a long barrel high velocity 75/76mm gun. The Super Sherman built after the war had a US 90mm and it required a larger turret to accommodate the gun. The turret of the standard Sherman could take a low velocity 105mm howitzer, but it could only take a high velocity gun of around 75mm.

Bill

When they put the 17 lber (76.2 mm, not exactly 3") in the Sherman they had to modify it & rotate it sideways 90 degrees, and the enlarged "high" rear turret bustle (an armoured box) acted as a counter-weight.

When designing the Comet tank, they produced a modified version of the 17 lbr and named it the 77mm . Like the US army 106mm and 107mm weapons, it was not actually that caliber. It also only ever equipped that tank. Can't remember if it fired the same ammunition as the Fireflies. I think the answer is 'no', hence the 77mm moniker, even though it was also a 76.2mm caliber weapon.

Eventually the first model Centurions could mount the 17 lbr right-way-up, but they soon moved on to the 20 lber OQF rifle, which was essentially an evolved 17 lbr. A decade or so later, when the T55 arrived, the 20 lbr was rebored, (it still fits the Centurion turret mountings), and turned into what became the NATO standard 105mm.

So, there you have it. The majority of the western world's tank fleets used the evolved 17 lbr gun for about 50 years [;)]