What are the caliburs of British guns?

[Jh316]

Them being listed in pounds makes it harder to quickly compare them with those of other countries.

[Dragoon 45]

2 Pdr is a 40mm, 6 pdr is 57mm, 17 pdr is 3" or 76.2mm, 18 pdr field gun was also a 3" gun. I believe the 25 pdr is 94mm but not sure. The Brit system for naming guns is quite confusing sometimes. Some of their guns were named after the weight of the shell and some like the 5.5" gun named after the bore size. Also the OQF designation stands for Ordinance Quick Firing. There was also a 3 pdr used in some of the pre-WW II tanks that I believe was a 47mm, but do not quote me on that. They also had different marks of the same gun which sometimes referred to improved guns (i.e. increased barrel length or improved shells) or to improved carriages. While I am sure there is one out there someplace I have never seen a chart that gave the bore size, shell weight, and barrel length for all the British guns.

The US 37mm AT and tank guns were copies of the German PAK-36 3.7cm AT Gun, of which samples were bought and then copied prior to the war. The British 6 pdr (British design) and US 57mm AT Guns are essentially the same gun with only some minor differences in the carriage and wheels. The 17 pdr was a distinctly British gun based on a 3" AAA gun of pre-war design. The US Army in 1944 inquired about purchasing some of them to arm US Tanks with but at the time British production was only capable of meeting British Army demand for the weapon.

ORIGINAL: Jh316

Them being listed in pounds makes it harder to quickly compare them with those of other countries.

[FlashfyreSP]

The 25pdr is an 87.6mm L/28 caliber gun.

[Jh316]

ORIGINAL: Dragoon 45

The 17 pdr was a distinctly British gun based on a 3" AAA gun of pre-war design. The US Army in 1944 inquired about purchasing some of them to arm US Tanks with but at the time British production was only capable of meeting British Army demand for the weapon.

Why did the US need to purchase British 3" guns? The M10 with a 3" gun is available in 1942, 2 years before trying to purchase the British guns. How are they different?

And if the British 3" guns were just better, why not buy the design and begin our own production?

[264rifle]

18pdr was 83.4mm. which strangely enough was the diameter of the 20pdr gun used in Centurian tanks.

The 17pdr may have been developed from a 3in AA gun but diverged very early. there were a few (100 ??) 3in AA barrels used for the anti tank role but aside from diameter had nothing in common with the 17pdr.

Sources disagree on the British offer/ American request of the 17pdr. Some say British offered early but were turned down by Americans (NOT INVENTED HERE). By the time the Americans figured out how much they needed it the British didn't have enough for themselves. It can take months if not 1-2 years to bring a gun from drawing board to production. And months just to retool a factory. changes in production mean changes in raw materal allocations.

American 3in and 76mm guns, british 3in and 17pdr all used different cartridge cases.

[264rifle]

The British 17pdr fired a 2lb heaver projectile 350fps faster than American 3in or 76mm guns. Fully the equal of the Panther 75mm.

[Nikademus]

ORIGINAL: Jh316

Why did the US need to purchase British 3" guns? The M10 with a 3" gun is available in 1942, 2 years before trying to purchase the British guns. How are they different?

And if the British 3" guns were just better, why not buy the design and begin our own production?

It was possible to equip a Sherman with the 17pdr vs. say, the 90mm AA gun that eventually debuted (modified of course) for the Pershing. As for building our own version....well apart from national pride, copying a weapon isn't always as easy as it seems on paper. IIRC....there was a great debate in German circles about whether or not to simply "copy" the T-34 quickly vs. develop a whole new design. A slew of excuses followed which led to the Panther. Putting on my cynical hat for the moment, despite some valid objections cited, in the end I think it came down again to "Not made here"

[264rifle]

Even if an army could get over the "not invented here" problem coping was not always easy. Converting from metric to english measurement is not quite as easy as it might appear.
Plan calls for 7mm plate. Rolling mill stocks 1/4in and 5/16. Do you get custom rolled plate or go a little thinner (maybe weaker) or a little thicker (heaver and might not fit the next part). Steel alloys sometimes were the "property" of the Steel mill that made them and couldn't be copied without a licience agreement. Thread pitches were different on screws, nuts, bolts etc. English used different thread pitches and measurements than Americans. different methods of casting or forging might give different results. Was original bolted, rivited, or welded out of several peices or cast, forged and machined out of one big piece?
How were the jigs and fixtures the held the parts while being worked on made???

Could all of this be overcome??? Yes but it isn't simply give the plans for a new AT-gun to a factory that is now making an AT-gun and saying "change over. we expect first delivery in 4 weeks."[;)]

[Dragoon 45]

Although I can't find it right now, I had read the 18pdr was 3" in bore size, what source do you have for your information? 18pdr was a pre-WW I field gun and a contemperary of the French 75.

Also I have read one of the reasons that US Ordinance Officers were less than sold on the 17pdr was that the gun had a tendency to produce flashover (propellent leakage) at the breach. To them this indicated a design defect and some safety issues for the crew.

ORIGINAL: 264rifle

18pdr was 83.4mm. which strangely enough was the diameter of the 20pdr gun used in Centurian tanks.

The 17pdr may have been developed from a 3in AA gun but diverged very early. there were a few (100 ??) 3in AA barrels used for the anti tank role but aside from diameter had nothing in common with the 17pdr.

Sources disagree on the British offer/ American request of the 17pdr. Some say British offered early but were turned down by Americans (NOT INVENTED HERE). By the time the Americans figured out how much they needed it the British didn't have enough for themselves. It can take months if not 1-2 years to bring a gun from drawing board to production. And months just to retool a factory. changes in production mean changes in raw materal allocations.

American 3in and 76mm guns, british 3in and 17pdr all used different cartridge cases.

[FlashfyreSP]

18pdr = 83.4mm = 3.3 inches

[264rifle]

Dragoon. I have the 83.4 in a number of soources. Are you perhaps confusing the 18pdr with the 13 pdr??
The 13pdr, which was a 3in gun, was a common British gun at the beginning of WWI and Looked an awful lot like the early 18pdr guns.

Another point of confusion is that the US in WWI made the 18pdr for the British under contract. When the US declared war the fastest way to get a lot of guns quick was to have the factories that were making weapons under contract to the British and French keep making them for the US. We were smart enough to rifle and chamber some of them for the same ammo. So the the US had several different 75mm (3in) field guns, the M1897A4 (French 75) the M1917 (18pdr lined down to 75mm) and the least known the M1916 (home grown design) also known as the "crime of 1916".

Some of these went back to Britain in the days after Dunkirk.

[Dragoon 45]

That maybe where my source got its information, the US relined 18pdr's. It is a book called "Artillery of the World" edited by Halberstadt.

ORIGINAL: 264rifle

Dragoon. I have the 83.4 in a number of soources. Are you perhaps confusing the 18pdr with the 13 pdr??
The 13pdr, which was a 3in gun, was a common British gun at the beginning of WWI and Looked an awful lot like the early 18pdr guns.

Another point of confusion is that the US in WWI made the 18pdr for the British under contract. When the US declared war the fastest way to get a lot of guns quick was to have the factories that were making weapons under contract to the British and French keep making them for the US. We were smart enough to rifle and chamber some of them for the same ammo. So the the US had several different 75mm (3in) field guns, the M1897A4 (French 75) the M1917 (18pdr lined down to 75mm) and the least known the M1916 (home grown design) also known as the "crime of 1916".

Some of these went back to Britain in the days after Dunkirk.