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17 pounder vs 76mma2


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SFC_Storm #1 Posted Nov 02 2011 - 19:20

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So I have read alot about how much better the Firefly`s gun was than the 76mm.

I have heard some say it was better because the Brits made it top priority to issue them Solid ammo where as the 76mm only had few to use.

But I suspect the reason it had so much better Pen was either Projectile shape superiority or the actually shape of the casing creating wya wya better and effecient burning in chamber.

Its similiar to a .223 vs a .222 mag the .222 simply out classes it in speed and pen vs Body armor but the .223 is best for spall dmg.

Same as 30-30 Rounds they suck with FPS because they have no necks and there fore powder burns slower and more equal.

My question is do we have a ballistics expert here who knows why the 76mm/17 PNDR was so much faster than our 76mm? More powder? Better aero dyn`d Round? Better case design?

Please explain, Also I seriously cant wait for the firefly, it will be like the Ez8 but hit with the panthers 75/100 pen might be a T7.

Thx in advanced.

Also my Fav tank was T23, they need to bring it back with the 17 pounder that alot of them had. And made a T7 crossover, infact im gona start a petetion on it :)

I would ask my engineer but he said the Brits were actually crazy about letting us US guys test there stuff and instead would just share data, but never let us test them [Or rarely]

Ketnix #2 Posted Nov 02 2011 - 19:43

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I beleive I understand one factor is that the 17 pounder used something like 2.5kg more propelant.

thejoker91 #3 Posted Nov 02 2011 - 19:47

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Actually, even though they are the same diameter, they are VERY different rounds.

This is the 17 pounder projectile:
Posted Image

This is the 76mm projectile:

http://www.worldaffa...9c56_mainpi.jpg


The 17 pounder is a 76x583mm shell while the M1 is a 76x539 shell.

The 17 pounder is also a tappered case while the M1 is a straight case.

All in all, the 17 pounder had much better muzzle velocity ( 884 m/s vs 792 m/s) and it was slightly heavier at 7.8 kg vs 7 kg of the M1 shell with a better cross section.

Akantha #4 Posted Nov 02 2011 - 20:07

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when the pershing>T23 change was made they said the T23 may become a premium some day. thats probably on the back burner now though :/

theshiyal #5 Posted Nov 02 2011 - 20:15

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View Postthejoker91, on Nov 02 2011 - 19:47, said:

Actually, even though they are the same diameter, they are VERY different rounds.

This is the 17 pounder projectile:
Posted Image

This is the 76mm projectile:

http://www.worldaffa...9c56_mainpi.jpg


The 17 pounder is a 76x583mm shell while the M1 is a 76x539 shell.

The 17 pounder is also a tappered case while the M1 is a straight case.

All in all, the 17 pounder had much better muzzle velocity ( 884 m/s vs 792 m/s) and it was slightly heavier at 7.8 kg vs 7 kg of the M1 shell with a better cross section.

WOW!!! no wonder its better look how much huger it is!!!  jk.  Kinda about what I figured there with the specs.

Does it annoy anybody else when people driving Easy8s talk about their 17pounder?  Kinda does me.

Ogopogo #6 Posted Nov 02 2011 - 20:17

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It has a good kilogram and a half more propellant if I remember correctly.

Sabertoothpython #7 Posted Nov 02 2011 - 20:20

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17 pounder looks like it would get more pressure within the shell, and depending on the powder load it may of had much higher fps than 76mm. Also, what kind of barrel did the 17 pounder fire from

SFC_Storm #8 Posted Nov 03 2011 - 05:26

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View Postthejoker91, on Nov 02 2011 - 19:47, said:

Actually, even though they are the same diameter, they are VERY different rounds.

This is the 17 pounder projectile:
Posted Image

This is the 76mm projectile:

http://www.worldaffa...9c56_mainpi.jpg


The 17 pounder is a 76x583mm shell while the M1 is a 76x539 shell.

The 17 pounder is also a tappered case while the M1 is a straight case.

All in all, the 17 pounder had much better muzzle velocity ( 884 m/s vs 792 m/s) and it was slightly heavier at 7.8 kg vs 7 kg of the M1 shell with a better cross section.

Ty I thought it was the necked up shape was the culprit, just like the old 30/30`s which are just big pistol rounds, The Necking makes the explosion insde alot more directed meaning more Energy, thx man for clearing it up. Im great with small arms since I was trained on most every weapon. I assumed it was propellent and shape but thx.


This is why the 90mm had such great velocity as well

http://www.lonesentr...gun-90mm-m3.jpg

Also this is the 20 pounder [85mm]

http://www.armoureda.../20 Pounder.jpg

Lol look how thin the neck is on the 20 Pounder, also its the length of neck that makes rounds move faster.

Here is german 88mm
http://www.lonesentr...ition-fig70.jpg

Its also necked, but the neck is alot less than others. But its funny it only Penned 111mm at 500m @ 30 degrees

Russain 85mm and Pen [No one can tell me there tests are better than US or German...Thats lol They made the worst of everything quality wise in the war why would Ammo be different]

Looks like a poor design to me.
http://www.worldaffa...9c56_mainpi.jpg

Ruski 100mm
http://www.scale-wor...52/HSR35008.jpg
Looks to be alot better round shape wise.

thejoker91 #9 Posted Nov 03 2011 - 15:35

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http://milpas.cc/rif...ion/tankger.jpg

Here you have some more ammo.

In order from left to right:

37x249R: 3,7 cm Pak / Kwk AP
50x289R: 5 cm L/42 Kwk Pzgr 40
50x420R: 5cm L/60 Pak 38
75x243R: 7,5 cm L/24
75x495R: 7,5 cm L/43 and L/48: later Pz IV
75x640R: 7,5cm Kwk 42 L/70: Panther tank
88x571R: 8,8 cm L/56: Tiger 1
88x822R: 8,8cm L/71: Tiger 2

Here you can see why the Panther gun had better penetration than the short 88 and why the long 88 had such outstanding performance, thats one huge round.

zT33A #10 Posted Nov 03 2011 - 17:12

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The 17pdr propellant capacity was large enough that it was used (necked up) with the 20 pdr centurion and the 105mm for the L7/M68.  They kept improving propellant and projectiles but the cartridge case remained basically the same until its replacement by the 120mm and its caseless ammo.  I believe velocities exceeded 1000m/s on some apds/apfs rds towards the end of the run.

SFC_Storm #11 Posted Nov 03 2011 - 19:08

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View Postthejoker91, on Nov 03 2011 - 15:35, said:

http://milpas.cc/rif...ion/tankger.jpg

Here you have some more ammo.

In order from left to right:

37x249R: 3,7 cm Pak / Kwk AP
50x289R: 5 cm L/42 Kwk Pzgr 40
50x420R: 5cm L/60 Pak 38
75x243R: 7,5 cm L/24
75x495R: 7,5 cm L/43 and L/48: later Pz IV
75x640R: 7,5cm Kwk 42 L/70: Panther tank
88x571R: 8,8 cm L/56: Tiger 1
88x822R: 8,8cm L/71: Tiger 2

Here you can see why the Panther gun had better penetration than the short 88 and why the long 88 had such outstanding performance, thats one huge round.

SorrY I dont see any picture, but quoting it I do :) thx

DerJager #12 Posted Nov 04 2011 - 03:38

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The 17.6mm QF 17lber had an overall cartridge length of about 1.4 times the length of the 76mm M1A1.

Both used APCBC as their main ammunition, the 17lber just fired it to higher velocities.

anglomanii #13 Posted Nov 06 2011 - 23:52

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from the info i have seen (on towed and british tanks), the 17pdr while having a much bigger charge, was so much better simply due to the optics used and as well as the recoil and shell ejection/loading equipment, from what i can gather it simply meant that the british tanks where able to spot targets at longer distances more accurately and shoot faster with less recoil and need to relay the gun. it was supposedly a little different on the firefly but i don't really have enough info to speculate.

Dominatus #14 Posted Nov 07 2011 - 00:01

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View Postanglomanii, on Nov 06 2011 - 23:52, said:

from the info i have seen (on towed and british tanks), the 17pdr while having a much bigger charge, was so much better simply due to the optics used and as well as the recoil and shell ejection/loading equipment, from what i can gather it simply meant that the british tanks where able to spot targets at longer distances more accurately and shoot faster with less recoil and need to relay the gun. it was supposedly a little different on the firefly but i don't really have enough info to speculate.

The M1A2's improved breach might be similar to the 17 pdr's but I'm not sure. A lot of adjustments had to be made to the Firefly's gun for it to fit. One such change was rotating the gun sideways.

DerJager #15 Posted Nov 07 2011 - 01:23

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17lber didn't have any better recoil mechanism than the M1 76mm when both were mounted in a tank.


And the M1 had a higher ROF than the 17lber, (significantly higher, infact. In the M4's turret, it was about the same as the KwK 36 88mm L'56.).

Standard zoom of the 17lber was 3x as opposed to the M1's 2.5x. It could be doubled to 6x, but that also reduced the effective firing range, because you would loose some accuracy (as I understand it, the brits put the secondary optical lens INFRONT of the gunsight markings, so it also magnified the markins, making them inaccurate).

Dominatus #16 Posted Nov 07 2011 - 01:41

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View PostDerJager, on Nov 07 2011 - 01:23, said:

17lber didn't have any better recoil mechanism than the M1 76mm when both were mounted in a tank.


And the M1 had a higher ROF than the 17lber, (significantly higher, infact. In the M4's turret, it was about the same as the KwK 36 88mm L'56.).

Standard zoom of the 17lber was 3x as opposed to the M1's 2.5x. It could be doubled to 6x, but that also reduced the effective firing range, because you would loose some accuracy (as I understand it, the brits put the secondary optical lens INFRONT of the gunsight markings, so it also magnified the markins, making them inaccurate).

That the M1A1 or M1A2? Or something else like the M1A1c? As to 17pdr's RoF in a tank, what about on Challengers and such?

DerJager #17 Posted Nov 07 2011 - 04:49

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Both. The M1A2's ROF fire advantage is exagerated in game. The M1A1 just had a shortened barrel, M1A1c just had a shortened barrel and a muzzle brake, and the M1A2 I think was essentially the same as the M1A1c, but with a slightly (emphasis on slightly) modified breech.

An M4 sherman armed with a 76mm gun and a good crew could probably have managed about 19-20 rounds per minute in a short burst. After a bit though, the crew would begin to get tired, and the ROF would likely have slowed down down below 17 RPM and down into the 12-14 RPM range.

Remember, they're doing strenous work inside a closed up inside a metal box in the middle of summer with the sun beating down on the tank.


I'm not entirely sure about the Challenger or post-WWII tanks. My area of expertiese is WWII tanks, aircraft, and infintry weapons. I suspect that it would be somewhere closer to 14-15 rounds per minute, perhaps even 16-17.

wyatt022298 #18 Posted Dec 03 2011 - 00:02

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17 pder used a good bit bigger charge, thats all.




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