Differences between the "Type 99" and MG-FF?

[Karnak]

Tony,

Are you working on any new books?

[Tilt]

Originally posted by Tony Williams


To be precise it is the combination of ballistic coefficient and muzzle velocity which determine the range.

Ballistic coefficient is important because it determines the rate at which the projectile slows down (the "aerodynamic drag", if you like).

I miss a refernce to a "ballistic coefficient" in "Rapid Fire"

I note an approach to the subject in p28  (momentum...which is also mass x speed) however I have been arguing to show that the muzzle energy is the better simplistic describer (as stated on p29) of range rather than weight and drag (which ignores the muzzle velocity).

I note that p16 explains that range was sacrificed by going to a lighter shell on a particular round type even tho muzzle velocity was increased however I assume that the net muzzle energy was also reduced when going to the lighter shell too?

eg What was the muzzle energy of the 20 x 82 HE compared to the (slower but heavier) 20 x 82 AP/HE (I only see figures for the HE)

of interest then from this discussion is a comparison of range for the 20 x 82 HE and the 20 x 99R HE. The 99R has lower drag and higher muzzle energy...........I would expect its flat trajectory to be significantly longer?

Would it be possible to add a section on the physics of ballistics (both propellent and  explosive) and trajectories plus a  comparaive assessment of  various rounds ............in one of your future works?

Tilt

btw I fully concurr with both your and Hohuns comments on ballistic/ kinetic variances at target.

[HoHun]

Hi Tony,

German documents indicate that the MG151/20 mine shells were about 3.75 times as effective against four-engined bombers as the MG151/15 projectiles.

The kinetic energy the 15 mm projectiles carried was about 3.3 times that of the 20 mm shells for the same effect.

The 20 mm mine shells contained 18.7 g explosives, the 15 mm HEI shells 2.8 g each.

Do you happen to have a comparative value for the Hispano HEI shells?

Regards,

Henning (HoHun)

[Tony Williams]

I am, this weekend, finalising the next book for sending to my publisher, which is scheduled to be in the shops in March next year (no, don't ask me why it takes so long).

It is the first of a three-book series on the development of aircraft gun, ammunition and installations. My co-author is Emmanuel Gustin, who knows a lot more about aircraft and installations than I do. The first volume covers 1933-45, the next will be 1914-33 and the last 1945-2002. The first volume looks as if it's going to be twice as big as the others...

I have been spending a long time collecting as much info as I can concerning ammunition loadings, HE weights, composition and performance, plus AP performance, from a wide range of sources (thanks, Brady and Henning, among many others!).  Some interesting comparative information came from British tests on German and British ammo during WW2.

The issues of sectional densities, ballistic coefficients and range are covered, and I have ballistic data on the German ammo in particular.

To answer the question, the Hispano shell held 10-11g of HEI.

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/

[brady]

TY sir:)

[Urchin]

Ok, one more question.  Assuming you can hit with the MG-FF on the 109E4, each shell that hits should be roughly equal in damage to the Mg151/20?  At least if I read that right.  

In Aces High, it isn't even close.  The single Mg151/20 in the nose of the 109F4 does WAY more damage than the wing-mounted MG-FF's in the 109E4.  And it is easier to hit with to boot.

That would seem to indicate one of two things to me:

1.  The MG-FF doesn't hit as hard as it should be hitting.
or
2.  The MG151/20 is hitting harder than it should be hitting.

They aren't even close to the same hitting power.  And no, I haven't run any scientific tests to 'prove' it, although they'd be fairly easy to run I think.  I'm just making that claim on the basis of my experience in the various 109s, in Aces High (which admittedly isn't scientific in the least).

[Tony Williams]

The MG 151/20 should certainly be easier to hit with, for two reasons;

1. The projectile has a shorter flight time due to the higher MV.

2. The gun is centrally mounted, right under the sights, so there's no harmonisation problem.

There shouldn't be a significant difference in hitting power, although the API shells which were usually included in the belt mix would obviously have more kinetic energy.

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/

[illo]

So i would like to ask why hizookas are so effective in AH?

MG/FF M (109E, 190a5) 690m/s
MG151/20 790-805m/s
Mgeshoss 18.6g NP/HA40 (round 92g)

HS II 880m/s
HE/I 10-11g of ?TNT? (Also didn't they had problems with HE fuse - explosions outside fuselage, so AP/I was used instead)
AP/I 4.2g thermit, incendiary.

And yes, once again Mine round fired from MG/FF M and MG151/20 has equal hitting power. About 4 should be enough (75g of explosive) to destroy most single engined aircraft. (Note MK108 M-round 72g of explosive). Effect would much depend on construction of opposing aircraft.(Whether overpressure could build up easily or not, ie. wood skinned aircraft could usually absorb more hits than aluminum ones)

Ps.Sorry no mean to hijack this thread

hmmm...one thing im also interested about. How about effect of vibrations caused by airflow on wing mounted MGs/cannon? How much it causes dispersion?

[Karnak]

illo,

AH's damage model seems too simple to me to do adequate justice to the complexities of WWII aircraft armaments.

Consider that the AP round of a Hispano Mk II is most likely going to just make an entrance hole and an exit hole on a bomber due to the large amounts of bomber that aren't critical systems or structure, but rather just skin.

A Hispano Mk II AP round hitting a fighter, on the other hand, is much more likely to hit a critical system such as the engine, fuel, pilot or main spar (which it would break).  I suspect that AP rounds would be just about as effective at killing fighters as the German Mine rounds.  The German Mine rounds would, however, be much, much more effective at killing big aircraft like B-17s and Lancs.

[illo]

Nice little ammunition chart for you. (not for you tony, hohun. you already have one)

[illo]

Karnak.

Yes, I agree. Ah models only heavy structural damage. (lost wings etc.)
With current DM AP rounds wouldn't have much to damage, while real fighters interior was full of more or less vital/vulnerable parts/systems.

[Tony Williams]

Originally posted by illo
So i would like to ask why hizookas are so effective in AH?

MG/FF M (109E, 190a5) 690m/s
MG151/20 790-805m/s
Mgeshoss 18.6g NP/HA40 (round 92g)

HS II 880m/s
HE/I 10-11g of ?TNT? (Also didn't they had problems with HE fuse - explosions outside fuselage, so AP/I was used instead)
AP/I 4.2g thermit, incendiary.

A couple of points.

First, M-Geschoss was never exclusively loaded in 20mm fighter gun belts; it was mixed with conventional HE-T (which only contained 3.7g HE) and API.

The Hispano HE was loaded with Pentolite (PETN+TNT) or Tetryl (US), the HEI had Tetryl (7g) and incendiary (4.3g).

The first version of the Hisso HE in RAF service had a superquick fuze which was ineffective, so until they developed a delay action fuze for the HEI they briefly reverted to a plain steel ball projectile as being more effective. The HEI was then mixed in the belt with SAPI, which contained 11g incendiary compound.

The question of aircraft damage has so many variables that it is difficult to generalise. When the RAF tested the German 20mm against the Hisso, they concluded that although the M-Geschoss was highly effective when it exploded in a confined space (eg a wing box), the Hisso would penetrate deeper and stood more chance of inflicting structural damage.

The M-Geschoss achieved its maximum effectiveness in 30mm calibre; the MK 108 was really designed around it, and fired nothing else.

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website: http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum: http://forums.delphiforums.com/autogun/messages/

[illo]

Thanks tony. Much new information for  me. Anything about when and which hispano ammunition type was generally used? (1940-45)

[HoHun]

Hi Karnak,

>I suspect that AP rounds would be just about as effective at killing fighters as the German Mine rounds.

While the fighter may have a larger proportion of vital components making it a better target for armour piercing rounds, it also features much smaller confined spaces which makes it much more vulnerable to mine shell hits, too.

German research indicated that a fighter's proportion of areas vulnerable to mine shells was even larger than a bomber's, and actually included almost the entire airframe.

I don't see any reason to assume that the relative effectiveness of mine shells versus armour piercing projectiles against fighters was any different than against bombers.

Regards,

Henning (HoHun)

[Tony Williams]

Originally posted by illo
Thanks tony. Much new information for  me. Anything about when and which hispano ammunition type was generally used? (1940-45)

I believe that the changeover from HE through ball to HEI took place during 1941. Certainly by 1942 the RAF standard load was 50/50 HEI/SAPI, and it stayed that way thereafter.

Incidentally,the SAPI was a standard HE shell body with a hard steel cap instead of a fuze. The incendiary mix was ignited by the force of impact. It was capable of penetrating around 20mm armour - which was enough.

The RAF never used an AP shot, but the USAAF did adopt one (the M75). I don't know what use they made of it, though. The HE/HEI rounds for the USAAF were to the same spec as the RAF's, but I don't think they used SAPI.

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine
guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/