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The 3pdr gun dated to black powder days (and did the old 6pdr used in WW I tanks) although modern (post 1900) ammunition used smokeless powder ballistics were not improved much.
There was never an AP projectile for the !3pdr and there was never a chemical or smoke projectile.
The WW I 12pdr and 13pdr guns were NOT even approaching HIgh Velocity. The 13pdr fired a 12.5lb projectile at 1675fps. The US 75mm field gun (French 75mm decedent) fired a 14.7lb HE shell (or 14.96lb AP shell) at 1955fps (2000fps for the AP).
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Yes one could be built, but it was it's small capacity that saw production dropped during WW I and the 18pdr taking over just about all duties except accompanying the calvary. the 13 pdr was expected to keep up the cavalry moving at the gallop using a 6 horse team.
Impressive in it's way but not really the criteria for selecting a tank cannon.
There were under 500 13pdrs built, production stopped early in WW I, production was never resumed, ever. The converted AA guns came out of that under 500 guns.
The fact that a small number of guns were brought out of store and mounted in some pillboxes in the dark days after Dunkirk in no way changes the fact that the gun was obsolete during WW I and in no way was a starting point for a gun that would leapfrog the UK into the forefront of AFV design.
The 13pdr HE shell (like many British HE shells) carried a smaller than usual HE payload (9 oz 4dr/262 grams) compared to the American 75HE which held 1.5lbs of TNT or 1.36lbs of Amatol.
It might be tempting to make more of the 3.7" QF Mountain Howitzer used in the A 9/10 etc. but a look at it's performance shows it to have a very low velocity and limited HE capacity
785 m/s for a 3 lb projectile - excellent for the era.
Sorry for the missprint, I meant 13pdr but yes, you need a nuclear reactor, or at least some way of making chemical or smoke round much, much more effective. 75mm was considered the smallest practical smoke/chemical round as anything smaller simply didn't carry enough payload. British 13pdr shell was certainly suspect in this regard. British loved ot make shells out of crappy steel which meant several things, easier and cheaper to make so supply is easy, but you need a lot more for them for the same target effect. Crappy steel means thicker shell walls to stand up to the firing stress so less room for payload. the 13pdr firing He would have been useful, just not as useful as the shell weight and caliber suggest.Do we need a working nuclear reactor to have the AP, chemical or smoke projectile for a 3lb Vickers?
http://www.navweaps.com/Weapons/WNBR_3-40_mk1.phpThis ww1 12pdr cannon is certainly above the 2000 fps league, let alone the 1700 fps league: link
British don't need to match Americans here.
What they need is a good gun, be it as AT or tank gun, that is much better than what they fielded in these roles, and pronto.
A 2pdr (40mm) HE shell was designed but the explosive charge was deemed to small. There was a 40mm HE mortar shell, but perhaps the HV of tank guns requires a thicker shell wall and thus reduced HE charge.starting here.
There was no real reason the 2pdr and 6pdr couldn't have had HE ammo from day one.
which 3pdr was that?
the one in the Vickers tank of the 20s was good for 533m/s or 563m/s.
The Naval 3pdr was a rather large and heavy gun. Only about 100lbs lighter than the 6pdr anti-tank gun. If you are going to stick a 99in long 650lb gun (barrel and breechblock) in a tank it better do more than this 3pdr.
Sorry for the missprint, I meant 13pdr but yes, you need a nuclear reactor, or at least some way of making chemical or smoke round much, much more effective. 75mm was considered the smallest practical smoke/chemical round as anything smaller simply didn't carry enough payload. British 13pdr shell was certainly suspect in this regard. British loved ot make shells out of crappy steel which meant several things, easier and cheaper to make so supply is easy, but you need a lot more for them for the same target effect. Crappy steel means thicker shell walls to stand up to the firing stress so less room for payload. the 13pdr firing He would have been useful, just not as useful as the shell weight and caliber suggest.
Since a general rule of thumb for armor penetration is that it goes up with the square of the speed (everything else being equal) so 17 X 17 = 289 while 20 X 20 = 400 so the 1700fps gun has 72% of the penetration of the 2000fps gun, except the 2000fps gun is using a heavier projectile. for given caliber and impact velocity penetration is directly proportional to shell weight. So yes you do need something extra tricky to get the 13pdr up to the standards of the day.
Britain 12-pdr [3"/40 (7.62 cm)] 12cwt QF Marks I, II and V - NavWeaps
The problem isn't getting a 12-15pdr cannon (75-76mm) cannon with good performance, it is getting one that fits in a tank, or at least a tank of the time. While some may shrug off the idea of a few hundred extra pounds of weight in a 15-25ton tank the fact is that the heavier gun creates a Domino effect. You need a larger turret, which has to be balanced to rotate properly. Using old naval or coast defence guns was done but it was hardly ideal. The gun in the American M-10 tank destroyer was an old (pre WW I) coast defence gun. The 76mm gun in the Sherman fired the same projectiles using a much smaller cartridge case (new propellants) out of a much lighter barrel (new steel alloys and manufacturing techniques)
If you are just looking for some sort of HE capability (equal to a hand grenade?) , the 2pdr could have been supplied with HE ammunition from day one. The failure was not the weapon but doctrine. The 2pdr HE ammunition that was supplied later in the war held about 63-65 grams of HE. While certainly not great it beats the heck out of german 37mm ammo which held about 25 grams of HE. German 50mm HE ammo held about 165 grams.
British alos cheaped out on the AP ammo.
see : http://www.wwiiequipment.com/index....er-anti-tank-gun&catid=40:anti-tank&Itemid=58
the APCBC shot, first made in 1943 had a penetration at 1000 yds equal to what the early shot (pre war) did at 500yds. At 500 yds it was nearly equal to the old shot at 100yds.
The British had been making APCBC shot for naval guns since before WW I, it didn't require anything new in either materials or knowledge.
Build the 6pdr earlier, the plans had been completed in 1938. Same thing, make HE ammo from day one, make APCBC shot from day one.
There was a 6pdr coast defence gun that used a different cartridge case. It's most famous use was at Valetta Malta, 35/36 July 1941.
A 6pdr AA gun had a shell with an 8 oz (225 grams?) of filler.
Both guns were limited in range by the shoulder controlled elevation making follow up shots difficult, not by the accuracy of the guns or ammo.
Had road transporters been readily available so many options are opened up. For starters, build the tank around three men in the turret. Conduct ergonomic and operational efficiency studies. on wooden mock-ups.The problem of tank size has also been noted twice now and cannot be underestimated. A stable mobile platform for a large gun requires
weight. Mid to late 30's British tanks just weren't that big due to transport size limits imposed on designers.
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The problem of tank size has also been noted twice now and cannot be underestimated. A stable mobile platform for a large gun requires
weight. Mid to late 30's British tanks just weren't that big due to transport size limits imposed on designers.
We don't have the 6pdr gun, unlike the Naval 3 pdr . So I'd stick a better gun than it was either mid-speed 3pdr or the 2pdr on a tank and call it a day. The 2pdr does not offer anythin even over the interwar, mid-speed 3pdr found on British tanks.
The 12 or 13 pdr HE shell made from crappy steel still beat the cr@p out of the 2pdr, 3pdr or 6pdr shell made from crappy steel. The 12 pdr smoke or chemical shell is again much better than 6 pdr one.
You will note that I've suggested he 12lb 12cwt gun, it fired at ~2230 fps, or 200-400 fps better than the US M3 75mm found on Shermans or Lees.
I'm not looking just for 'some sort' of HE capability, but rather finding a way for overall increase in British tank and AT gun lethality against any likely targets, on budget and on time. Reinventing the wheel (= design & producing of 2 and 6 pdr) goes against these goals.
We don't exactly know when ww2 will start. For example, Munich talks ending up without the Czechs being thrown under a bus probably means war in 1938, hence the all new and shiny 6 pdr is too late.
The myth of railroad-imposed limits on British tank's size is long past it's exipiry date. The Vickers Medium Mk.II of mid-1920s was produced in several hundreds, and it was as wide and as tall as the Pz-IV. There was one or more reasons why many British tanks conceived in 1930s were both narrower than needed and under-gunned, however transport requirements were not among the reasons.
The British loading gauge was less than that used in continental Europe due to the British system being so much older so the rail limit is not a myth. The Matilda II was
narrower than the Panzer IV but not that much. The main difference is that it was heavier by several tons. The MKII was under half the weight of the Matilda II as well.
It is true that there were other design constraints such as bridge weight limits and the requirement for the fighting compartment of the tank to be between the tracks / suspension to keep height down.
These constraints applied until 1943.
The other major problem for the tank force was the budget. Priority went to home defence which meant the RAF and RN received the bulk of available funding.
All of these factors had a bearing on design and adoption.