Author Topic: 5"/38 Cal MK12 vs T13E1 75mm (Read 1885 times)

Baumer · « **on:** February 27, 2008, 04:47:05 PM »

Just a general question about the effectiveness of the 5" guns on the carrier and cruiser. It was my understanding that they were modeled from the 5"/38 cal Mk12 used on most US ships of the time period. And the cannon on the B-25H is a T13E1 correct?

I was practicing off line and noticed that it takes 9 rounds from a B-25H to sink a cruiser and 13 rounds from a 5 inch gun firing HE. That seems a little odd to me, the Mk 12 fires a 55lbs shell and the T13E1 fires a 14lbs shell. Does anyone have an explanation for why this is this way? I'm not sure if I'm missing something, I know the relative motion of the plane should help the 75mm velocity but is 250 mph that big of a difference?

Thanks,
Baumer

Major Biggles · « **Reply #1 on:** February 27, 2008, 04:50:15 PM »

were you usig the HE or AA shells on the 5" gun?

Baumer · « **Reply #2 on:** February 27, 2008, 05:06:06 PM »

I made sure I was firing HE. That was my first thought as well, but it's very repeatable. The only change I made to the off line arena was to enable damage for my country. I like to practice without all the other tracers around, could that make a difference?

Ghosth · « **Reply #3 on:** February 28, 2008, 07:41:47 AM »

Was just able to sink a enemy cruiser with 10 direct hits from 5" twin. There were 2 or 3 very close waterspouts next to the cruiser that I didn't count. Perhaps I should have, they may have more effect than we have been giving them credit for.

Funny that I couldn't get a waterspout from the 5" single so was very hard to range.

Nice digging Baumer!

Easy test setup, H2h, create lan setup, midway map (lots of fleets)
Moved one bishop fleet and one knight fleet so that they were aprox 5k apart.
(no aa firing) on side by side courses so it was easy to find range and keep hitting the cruiser.

I agree from past testing and flying in main that 9 HE rounds from the b25H WILL sink a previously untouched cruiser.

angelsandair · « **Reply #4 on:** February 28, 2008, 07:43:59 AM »

Well, the 14lb shell is going from 150-300 mph faster, so it acts as AP as well as HE

Karnak · « **Reply #5 on:** February 28, 2008, 11:13:27 AM »

Quote

Originally posted by angelsandair
Well, the 14lb shell is going from 150-300 mph faster, so it acts as AP as well as HE

Negligible boost and HE will get very litte AP boost by adding speed as it explodes on impact.

Also the cruiser should take well more than 10 5" hits.

Lusche · « **Reply #6 on:** February 28, 2008, 11:34:11 AM »

Quote

Originally posted by Ghosth
I agree from past testing and flying in main that 9 HE rounds from the b25H WILL sink a previously untouched cruiser.

You can take down a BH with 18 rounds (sitting on the gound, no added speed) and a cruiser with 9. In other words a B-25H 75mm shell has the destructive equivalent of 154-174 lbs bombs. Thats perfectly in line with the other 75/76mm guns (Panzer IV, T-34)

But considering that bombs have a much higher % of explosive filling than artillery shells (usually in the range of 5-15% for shells about 50% for bombs!), I find the destructive power of cannons vastly exaggerated in comparison to bombs.

EDIT: If the destructive equivalent of cannon shells would be toned down, the rocket-equipped SdKfz 251 would suddenly be a very valued tool for taking down towns

Baumer · « **Reply #7 on:** February 28, 2008, 01:01:33 PM »

I agree that the B-25 round is right in line with the other similar tank cannon's in terms of damage.

It just struck me as odd that the 5" round was weaker than I expected. I've been doing a little research for data and came across a rather interesting website with some good information on all kinds of naval guns.

http://www.navweaps.com/

It was interesting to see that given the overall effectiveness of the AA round, and that they seldom carried AP rounds shipboard. All they had to do was change the fuse to go from AA with a Mechanical Timed (MT) or Proximity (VT) fuse to HC with a Point Detonating (PD) fuse.

If you look under the ammunition area they quote numbers very similar to what Lusche stated for explosive charge per round weight. I believe it was something like 7-12%.

They quoted a "New Gun" muzzle velocity of 792 mps (Meters per Second). How does that compare with the 75mm? Just a thought,

usieric3 · « **Reply #8 on:** February 29, 2008, 12:18:23 PM »

What some of you may be missing is basic data; ballistics. The tube on the ship-borne weapon is vastly longer, creating greater velocity. The T13 is a modified version of a 75mm pack-howitzer used by mountain, glider and airborne troops. The longer the tube the greater the velocity and accuracy over extended ranges.

Stoney · « **Reply #9 on:** February 29, 2008, 12:56:48 PM »

Quote

Originally posted by Baumer
It just struck me as odd that the 5" round was weaker than I expected. I've been doing a little research for data and came across a rather interesting website with some good information on all kinds of naval guns.

The HVAR 5" rocket uses the Navy 5" projectile as the warhead. So, theoretically, the 5" HE on ship should be equivalent or close to a single 5" HVAR in destructiveness (excluding any kinetic damage). As just under 6X5" HVAR is equivalent to 1000 lbs of damage in game, it would seem that the relative power of the 75-76mm type cannons in game are a bit saucy...

passssao · « **Reply #10 on:** February 29, 2008, 01:14:23 PM »

Perhaps the angle of impact? in a plane you hit most from above, and in a cannon you hit most by the side.
Ships are more strong from side than from above, and i think in the short distance, the plane can place a more precise hit into engines room.

Just my opinion, salute all, passao

Baumer · « **Reply #11 on:** February 29, 2008, 02:00:56 PM »

I've been doing a little more research, and have come up with the following #'s for a comparison. The 5" data I found on the sight I included above, and the 75mm info I got from Wikipedia. Can anyone verify that the numbers below are correct? I know we don't have AP rounds in the game but I couldn't find the 75mm HE weight. This way it's an AP to AP comparison of relative force. The 5" HE weight is actually slightly higher at an even 25 Kg.

5" AP shell weight- 24.5 Kg
75mm AP shell weight- 6.32 Kg

5" average muzzle velocity (full charge) 762 m/s
75mm average muzzle velocity 619 m/s

given that F=MA (And if I can remember how to do this correctly

)

The 5" shell leaves the barrel at 19,354.8 Nm/s

(25.4*762=19,354.8)

The 75mm shell leaves the barrel at 3,912.08 Nm/s (6.32*619=3,912.08)

It's just me, but if the target were 1,500 yards away, I'd want to be much further away from the 5" target.

moot · « **Reply #12 on:** February 29, 2008, 03:45:11 PM »

Quote

Originally posted by Stoney
As just under 6X5" HVAR is equivalent to 1000 lbs of damage in game

Typo for 100 lbs?

Lusche · « **Reply #13 on:** February 29, 2008, 04:02:22 PM »

Quote

Originally posted by moot
Typo for 100 lbs?

No. A single 5" rocket equals 156lbs of ordonance in destructive power.

moot · « **Reply #14 on:** February 29, 2008, 04:45:02 PM »

Yeah that's makes it more of a typo for 100lbs than 1000lbs. Thanks.