Type 99MK I vs MK II 20mm Cannon in AH

[brady]

The Japanese type 99MK I cannon and the Type 99 MK II cannon fired the same projectiles, and in keeping with Japanese doctern aprox 4/5th's of the ammo chain was HEI, point detionation ammo. The Compleat rounds differed between the two in that the Later (MK II) rounds had Larger casings to hold more powder, but the working end was the same.

  OK bearing this in mind.....10Bears and I hoped into the SEA to do some testing, after a couple hours of testing using the C47 as a target and the A6M2 and the A6M5 as the firing platforms for the the two different cannon models we came to this conclushion.

  The type 99 MK I hits about half as hard as the Type II when fired from an equil range at the Goon. AT D 180 a Burst into the  fuslage just behind and bellow the wing took aprox. 10 to 15 Type 99 MK II cannon hits to cause it to snap the plane in two or explode the plane. The same effect from aprox. the same distance took 30 to 40 Type 99 MK I cannon hits to acheave.


   Now if the Shell is the same ( or suposed to be) what is the deal hear? MV must be the culperet, howeaver with a HEI round that would detonate on impact anyway why is this so? I can certainly understand why the rounds differ in their balisticts howeaver I am woundering why such a drastic decrease in effect once a hit is acheaved.

[Batz]

I thought the mk 1 was a small round (length wise). Do both the mkI and mkII hold the same explosive content?

[Tony Williams]

Both Types fired the same projectiles - it was only the cartridge case length which differed. See: http://www.quarry.nildram.co.uk/Oe1b.jpg
The Type 99-1 was the Oerlikon FF (20x72RB), the Type 99-2 the Oerlikon FFL (20x101RB).

The question of the effect of velocity on the damage inflicted by an HE shell is an interesting one, and not entirely clear. You have to remember that HE shells (with the partial exception of the M-Geschoss) did not damage by blast effect alone, but by a combination of kinetic and blast effects. The blast broke up the shell and sent fragments flying through the target, so the faster the shell was going when it hit, the faster the fragments would travel through the target. Also, not all HE shells had instant fuzes; in fact the most effective had delay fuzes, to give them time to smash their way into the structure; again, muzzle velocity helps here.

For a longer discussion of this subject, see: http://www.quarry.nildram.co.uk/WW2guneffect.htm
As you will see, the 20x72RB scores 12 for destructive effect, the 20x101RB scores 15. That is, however, only an estimate.

Tony Williams: Military gun and ammunition website and Discussion forum

[brady]

 To Quote Tony's own Sight:


"if the projectile is primarily relying on HE blast or incendiary effect, the velocity with which it strikes the target is almost immaterial. Provided that it hits with sufficient force to penetrate the skin and activate the fuze, the damage inflicted will remain constant. "




So a 50% diferance in the Destructive effect of the round as evidanced from my testing would not be correct in terms of preformance modeling. If we are to sight your figures from above they should be far closer to one another, somthing on the order of 80% as effective for the Type 99 MK I, compared to the Type 99MK II.


   Now My refrence source for this material is actualy in Storage presently I have some old scans on my harddrive(pic above) , in the Back of the Book I took this from It list's the fuze's and their carteristics, I wounder if an examanation of that data could bring the two closer together in terms of thier effect on impact based on the delay of the fuse. I may nead to go a drive tomarow. to get it.

 How do the Europen Rounds for these weapons difer from the Japanese rounds?


 Batz said:

 "I thought the mk 1 was a small round (length wise). Do both the mkI and mkII hold the same explosive content?"

  Aside from what Tony said above, the Scan clearly shows both Guns( Type 99 MK I and II) progectiles held the same explosive content, The compleat round length is listed Bellow the image of the prodjectile for both Types of Gun, the "Round" is the casing and the prodjectile.

   

       



   

[Tony Williams]

Originally posted by brady
How do the Europen Rounds for these weapons difer from the Japanese rounds?
 

The Swiss Oerlikon projectiles were pretty much the same as the Japanese ones. The MG-FF/M rounds were also similar in effectiveness, apart of course from the M-Geschoss.

I agree with you that there should not be a huge difference in destructive effect between the two. Probably the major advantage of the higher velocity of the 99-2 was that it improved the hit probability.

Tony Williams: Military gun and ammunition website and discussion
forum

[brady]

CC that Tony, again TY for you help in understanding this.

[brady]

I wounder if this issue will be considered revelent enought to warent change?

[HFMudd]

I hope so.  I hate to admit it but I got so frustrated in the CT attempting bring down F4F with the Type 99's Saturday that I have been playing in the MA on the Trinfinity terrain.*

The conclusion I reached was that AH overmodels the kinetic portion of the damage.  This is of course based on nothing other that pesonal opinion and, as always, I defer to Tony Williams.



* I do plan on seeking professional help.

[Pongo]

Originally posted by HFMudd
I hope so.  I hate to admit it but I got so frustrated in the CT attempting bring down F4F with the Type 99's Saturday that I have been playing in the MA on the Trinfinity terrain.*

The conclusion I reached was that AH overmodels the kinetic portion of the damage.  This is of course based on nothing other that pesonal opinion and, as always, I defer to Tony Williams.



* I do plan on seek professional help.

That would match the problems they had getting the Hispano down to earth.

[brady]

"* I do plan on seek professional help. "

   LOL, Ya I feal your Pain, I uped my dosage this week:)

[Rasker]

does AH model the differences between the earlier and later LW 20mm's?

[brady]

AFIK, they do, but LW ammo chain make up was different from Japanese load out's. Japanese were as stated above mostly HEI 4/5th's or their abouts while LW  Chains had a mixed load that changed over the course of the war.

[Urchin]

Oh I'd certainly agree that the kinetic portion is vastly vastly more important in Aces High than any explosive content of any shell could be.  

However, there is a very solid reason for this- I'll leave it to you guys to figure out.

[Batz]

but LW ammo chain make up was different from Japanese load out's. Japanese were as stated above mostly HEI 4/5th's or their abouts while LW Chains had a mixed load that changed over the course of the war.

The ancestor of the MG-FF was the German Becker cannon which saw service in WW1. After the war, the production rights were sold to a Swiss company, SEMAG, who developed an improved version and then sold on the designs to Oerlikon, another Swiss engineering firm named after the suburb of Zurich where it was based. Oerlikon developed the basic design further in three versions; low, medium and high velocity. The Oerlikon FF was the smallest of them (also sold to the Japanese Navy who called it the Type 99-1 and fitted it to the Zero fighter). The German MG FF was based on the FF F, but the weapon was entirely redesigned for German production techniques.

The recommended use of ammunition in the MG FF was as follows:

- 2 Minengeschoß m. Zerl.
- 2 Brandsprenggranatpatronen L'spur m. Zerl oder Brandgranatpatronen
- 1 Panzersprenggranatpatrone o. Zerl oder Panzerbrandgranatpatrone (Phospor) .......o. Zerl

The tracer was used on HE/I (Brandsprenggranatpatrone) or pure incendiary (Brandgranatpatrone) rounds. The latter was apparently a new development in 1944, intended to replace the less effective HE/I. The fifth round was a semi-AP projectile, explosive or incendiary. Apparently the main reason this was used instead of a solid AP round was that a solid projectile would have been too heavy.

Performance Specs

Manufacturer: Oerlikon
Caliber: 20mm
Weight: 28kg
Length: 52.8in
Muzzle Velocity: 600 m/s Rate Of Fire: 520 rpm
Round Type: HE, semi-AP, I
Round Dimensions: 20x80mm
Round Weight: 134g

[brady]

I think Urchin is being to cleaver again:) " The Allied High" nick name, for ah was after all earned:)