The pounder way

[Von_Mannteufel]

Could someone explain to me how that Pounder way to measure guns work? Though I've read a little on it on the net I couldn't understand how it works (Sometimes smaller pouds are "bigger" and vice-versa). Thanks in advance.

[Michael Kenny]

Put simply a 6pdr gun fired a 6 pounds (weight) shell, a 25pdr. gun fired a 25 pound shell and the 17pdr gun fired a shell weighing 17 pounds. Now I know that not every shell fired from these guns were exactly the 'given' weight (a 25 pdr. AP shell weighed 20 pounds/HE was 25 pounds) but that is the system.

[silverback]

I was always given to understand that this system of classification was a hangover from the days of smooth bored , muzzle loading cannon. If it makes sense,. the poundage is a reference to the weight of a solid spherical shot (cannon ball) of a given calibre.

[Johan Elisson]

2 pdr - 40 mm
6 pdr - 57 mm
17 pdr - 76 mm
18 pdr - 84 mm
25 pdr - 88 mm
60 pdr - 127 mm

The weight to calibre table isn't exactly correct, even if going with the old spherical iron/lead/whatever cannon ball weight with a certain calibre, but it is the origin.

/Johan

[Von_Mannteufel]

Thanks all for the explanation, which were the more effective?

[Polynikes]

Well the method of classifying a gun by the weight of its shot is no longer practiced but is, IMO, better than classifying by calibre.

For example, the M4 Sherman tank carried a 75mm gun, the British adapted it to carry their 17lb AT gun (which had a calibre of 76.2mm).

So on the face of it, the increase was 1.2mm yet, the 17lb gun was a Tiger killer, whereas the 75mm was a peashooter by comparison.

In North Africa, the British used mainly the 2lb gun on their tanks (Matilda II, Valentine, Crusader) which had a calibre of 40mm. The German tank guns were rated purely in calibre but I the long barrelled 75m gun of the Pz IV (L43/L48) had a weight of 15 lb. Kind of makes it easy to see why the British armour in North Africa fared so badly.

http://www.wwiivehicles.com/html/germany/guns.html

Things were a little better when US built M3, the M4 tanks arrived.

Cheers from Rich

[Polynikes]

2 pdr - 40 mm
6 pdr - 57 mm
17 pdr - 76 mm
18 pdr - 84 mm
25 pdr - 88 mm
60 pdr - 127 mm

The weight to calibre table isn't exactly correct, even if going with the old spherical iron/lead/whatever cannon ball weight with a certain calibre, but it is the origin.

/Johan

Also there was the British 3.7" AA gun (similar to the German 88mm but if anything, sperior in performance) which was used as the basis of the 32lb gun on the Tortoise.

The Centurion was also fitted with the 20lb gun.

[Darrin]

Well the method of classifying a gun by the weight of its shot is no longer practiced but is, IMO, better than classifying by calibre.

For example, the M4 Sherman tank carried a 75mm gun, the British adapted it to carry their 17lb AT gun (which had a calibre of 76.2mm).

So on the face of it, the increase was 1.2mm yet, the 17lb gun was a Tiger killer, whereas the 75mm was a peashooter by comparison.

In North Africa, the British used mainly the 2lb gun on their tanks (Matilda II, Valentine, Crusader) which had a calibre of 40mm. The German tank guns were rated purely in calibre but I the long barrelled 75m gun of the Pz IV (L43/L48) had a weight of 15 lb. Kind of makes it easy to see why the British armour in North Africa fared so badly.

http://www.wwiivehicles.com/html/germany/guns.html

Things were a little better when US built M3, the M4 tanks arrived.

Cheers from Rich

Of course 90% of the world uses the metric system now.

Even weight of shot can be misleading as even the sherman AP round was only a bit lighter than the 17 AP round. At the same time the sherman HE round was supposed heavier than the 17lb HE round.

The ger long 75 guns were rare in africa as well. By that time the britsh already had 75mm guns from other tanks as well as thier own 6 lb gun.

[Darrin]

Thanks all for the explanation, which were the more effective?

Thats a very difficult question since you are talking about different things on the battlefield. The 17lb was a very good gun to take out tanks with because it had a very high vel KE=mass times vel squared. Its performace was similar to a panthers 75mmL70 gun.

On the other hand it actually behaved much worse than the little pea shooter 75mm gun on the sherman at HE antipers performace. The lower vel guns for various reasons were better at HE antipers effects. So many of the actual targets on the battlefield were not arm targets they were ATGs, inf, horse, trucks, etc... The role of these shorter low vel guns is very important.

[Polynikes]

The 17lb equipped Sherman "Firefly" tanks were priority targets for the Germans though, apart from tank-destroyers, they were the only tank capable of taking out a Tiger or Panther at distance (though the Panther supposedly had the "shot-trap" whereby an accurate shot under the barrell would knock it out.

The British 6lb AT gun was a great improvement on the rubbish 2lb gun but was still only a stop-gap.

British tank design suffered from two interests pulling in different directions with the result that neither the "cruiser" nor "infantry" tanks were capable of mounting the 17lb gun when it finally appeared. A great pity because the Churchill had the makings of a good tank otherwise.

Even the Comet tank with it's supposed 77mm gun (it was actually a modified 17lb 76.2mm gun) had to reduce the power of the 17lb gun in order to accommodate it in it's turret.
The 77mm calibre was designated as such in order to distinguish it from the identical calibred round of the "real" 17lb gun.

Cheers from Rich

[Darrin]

The 17lb equipped Sherman "Firefly" tanks were priority targets for the Germans though, apart from tank-destroyers, they were the only tank capable of taking out a Tiger or Panther at distance (though the Panther supposedly had the "shot-trap" whereby an accurate shot under the barrell would knock it out.

The British 6lb AT gun was a great improvement on the rubbish 2lb gun but was still only a stop-gap.

Definatly and early in the summer of 44 when the 17lb gun was less common this was an issue. By the end of the war when almost half the CW shermans mouted 17 lb it was less of a problem. The US TDs and 76mm gunned sherman were just as rare as well and cold be targetted the same way.

In reality the 76mm gun was much less effective then the 17lb relative to the enemy tanks. The 76 mm gun could pen the sides of the tiger I and II fairly easy as well as the much thiner panther. The front of the later IVs. The 76mm could not easily pen the front of a tiger I with normal ammo but it could with HVAP tung rounds. But these were pretty rare in the US army and tended to be issued to TDs not shermans with 76mm guns. The sloped glacis of the Tiger II was vertually invul to the 76mm gun even with special ammo. The sloped galcis of the panther was also invul even with special ammo.

The 17 gun could at least pen the front of a tiger I with ease with normal ammo but these started dis from the battlefield in the summer. It gave a greater stand off dis to the side arm of all tigers with no arm. The tiger II glacis was still invul even with special ammo. The panther glacis could be pen with special APDS ammo but only when the ammo was working good and never with ease. The panther glacis sometimes were flawed from mid 44 on allowing even normal 17lb rounds to pen.

The 75mm gun could pen with diff the front of panzer IVs and sides of all tigers. It could easily pen the side arm of the panther. It couldn´t pen the front of the tiger I or glacis of either the tiger II and panther.

The CW 6lb gun on a chrchill I believe was the first tank to des a tiger in north africa.

[Polynikes]

There's a well trodden story about the Comet's first action, it pulled on to a road and spotted a Tiger.

The Tiger saw the Comet and mis-identified it as a Cromwell (with a weak 75mm gun). Knowing it was invulnerable from the front to the Cromwell gun, it slowly zeroed in on the Comet and was destroyed with a single shot of the Comet's (modified) 17lb gun.

Not sure how true it is but the 17lb gun was pretty damned effective. A pity it didn't come into service earlier and a REAL damned pity that tank design committees weren't talking to gun design committees!

That Churchill crew who took out a Tiger in North Africa were brave bastards!

Cheers from Rich

[Tony Williams]

A couple of comments:

The 2 pdr anti-tank was one of the most effective in the world in 1940; it was in a class above the comparable German 37mm PaK. The problem was that it was kept in service for too long.

The 77mm was a lot more than a 'modified' 17 pdr. The only thing it had in common was the shells it fired. The cartridge case was much smaller and generated a much lower velocity; about equivalent to the US 76mm. It was intermediate in performance between the German 75mm L48 and 75mm L/70. The British rounds are here:
;
the 17 pdr is the big one with the APDS shot, the 77mm is on its right, the US/UK 75mm on its left.

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