Ahhh back that far. Yeah I think there was a tweak to the ROF after someone dug up some better data. Thing is that they start off modeling something one way and then a whole bunch of people get in a frenzy and the ultimate benefit is that long lost documents that may once have existed only in a couple of places are found and tweaks are made if the data is good. Actually this flight simming hobby has probably helped gather allot of knowledge that was previously obscured for a very long time.

Salute

The rate of fire of the Mk108 is of the very best variation.

The real problem with this weapon is that bullet drop due to the very low velocity does not seem to be modelled.

This was a bomber killer weapon, completely unsuited to Fighter vs Fighter action.

Yet in the game, there is no real problem in firing the weapon from almost any horizon, including wings vertical. The bullet drop for anything off wings horizontal and level at convergence should be horrendous, but does not seem to be the case.

As usual and as for many of your post about (against?) the Me109,this is quite wrong Buzzaw...

Its 650 rpm ROF is comparable to a simple 20mm allied canon and at a short range it could blow out any *BIG* target like P51D,P47D and TempestMkV with a *single hit*.This wasn't a bomber-killer weapon,this was a *versatile* weapon.

BTW,at a late stage of the war,some 30mm shells did even see their self destruction system disabled,to increase the effective range of the gun.This doesn't seem to be modelled ingame,no complain about this Buzzaw,uh?

Other points:
The centerline position of that gun on Me109 permitts some interesting advantages:
-The gun recoil effect was partially reduced,thanks to the fuselage structure which is better suited for firing such a heavy armament (when comparing with Fw190-A with 2xMK108 in the wings)
-The aiming was also favorised by this kind of centerline placing,especially at short range.

IMHO,the Me109 was certainly the best MK108 piston carrier/user.
The Me262 jets were also dreadful monsters that brought all those good characteristics up to 4xMK108,still in the nose...





As far as i know,German army was absolute specialist in very high ROF canons...
Ingame,as already said,all is ok.

Let's do a simple test,

Set your game in "arcade mode",then
Realise a ~1 sec bursts on the ground with a Me109 with MK108,and look how many impacts you see.
Play with the timeset to increase the precision of your measures

Here is what i get,in 4.08m:





From 10 to 12 impacts on ground for each test,for one second burst => 650 rpm.

Same results from many patches...

BTW and IRL,a final improved version of MK108 had been tested and was able to reach 900 rpm (!) in the last stages of the WW-II:

From "Flying Guns, World War II" by Williams & Gustin [Airlife, 2003]"

"Towards the end of the war the MK 108A was achieving 900rpm on test, but this did not see service."

OMG...

Thanks to Peter for the info!

@+

In 4.08, Rof of MK 108 for K4 or Fw190 A8, for example is 660 Rps, and 500 or 525 m/s muzzle velocity, depending of used round.

Regards,

Josse

660 rpm and 500-525 m/s fits roughly with the numbers given by Tony Williams. The fact that they are slightly high compared with his figures should give Luftwhiners pause. :-)

I am puzzled about Busszaw's claim about bullet drop though. I thought the ballistcs in the game were physics-based, i.e. a projectile weight of X and a muzzle velocity of Y should give a trajectory that looks like Z (I assume projectile aerodynamics are not factored in).

Is this correct?

I after 7 years - who really cares anyway LOL

would be nice to see 8 .50s hit like 4 20mms so the 1 burst to kill any enemy cannon would equal out the armed and unarmed feel of the game. no matter what ac who ever bounces first and gets hits is usually the victor.

1 pass kills everytime vs 3-4 passes = so much more difficult. Thats why all the usa jockies fly german

Except me.

I fly Soviet.

Eight 50 Cals does not equal four 20 mms.

As you can see from the charts on Tony Williams's site those combinations are about equal in weight if fire, but that's without the explosive effect of the 20 mm shells. Clearly cannon are more destructive.

(Red line = six 50 Cals. Green line = four Hispanos.)


It's also why everybody switched to guns eventually. With the exception of the USAAF that switch was nearly complete by 1945.

Sorry, have to disagree since you have provided zero factual contradiction.

Let's look at the Mk 108 and compare it with the U.S. .50 calibre

Muzzle velocity 505 metres per second.

Compare that for example with the U.S. .50 calibre, which has a MV of 890 metres per second or nearly twice as fast.

Gravitational acceleration is 9.8 metres per second squared, or 32 ft per second squared.

What that means, is that in the one second after a round leaves the muzzle, it will normally fall approximately 4.88 metres or 16 feet due to gravitational acceleration.

There is no straight line for a fired round, all bullet paths are downward curves.

The Mk 108 round will have dropped approximately 4.88 metres or 16 feet at a point 505 metres distant from the muzzle. The .50 calibre will drop 4.88 metres or 16 feet at a point 890 metres distant from the muzzle.

It's more complicated than that. The round starts with a gravitationally acceleration of zero when it leaves the muzzle. As it moves away, the speed at which it moves downwards increases, so in effect, the further it is away from the muzzle, the faster it is falling downwards, and the further proportionately it has travelled downwards.

From this you can see the big advantages that high velocity weapons have, since most of the time, ranges are around 250 metres. A high velocity round like the .50 calibre will travel 250 metres much faster than the low velocity Mk 108 round, and the bullet drop difference between the two will be proportionately much greater.

WWII engineers compensated for bullet drop in their aircraft weapons by making the aiming point for the guns variable, and allowing ground crews to adjust them to compensate for gravitational acceleration. When we talk 'convergence', the ground crews were not only concerned about getting the bullets to come together into a focused stream, they were also compensating for gravity. The crosshair of the sights are lined up directly on the target, but the guns are aimed slightly upwards to compensate for bullet drop due to gravity.

Problem: In WWII aircraft, since 'convergence' is set up on the ground, at a firing butt, with the aircraft's wings level, compensation for gravitational acceleration of the round only works in actual combat conditions when the plane's wings are also level. When the wings are not level, it actually impairs the ability of the pilot to aim, ESPECIALLY when the weapon being fired is low velocity.

Example. A Mk 108 which has been set up with a convergence of 505 metres, in an aircraft which has its wings level, and which is fired at a target level target 505 metres distant will hit that target if the pilot puts the sight crosshairs on it.

If that same Mk 108, set up with that same convergence, aiming at the same target, at the same distance, now has its wings vertically banked to the right, the bullet will not hit the target, in fact the bullet will miss the target by a measurement of 4.88 metres to the right, and 4.88 metres downwards. That is because the convergence in this case, which has the gun aimed up to hit 4.88 metres higher than the target to compensate for gravity, now throws the round to the right, since the wings are vertically banked right. "Up" becomes right. Additionally, the normal effects of gravitational acceleration are still in effect, so the round accelerates downwards at the normal rate, and thus ends up 4.88 metres below the aiming point.

The Mk 108 was designed to fire at bombers, which are a stable non-maneuvering target, able to be fired at from level flight. In that role, it was quite successful, against hard maneuvering fighters, where the chances of a shot from a wings level position is vertually nil, it should be far less successful.

There are other factors which should weigh in on the Mk 108's effectiveness, among them bullet shape.

For example, for velocity retention, an aerodynamic round is very important, ie. one with a shaped nose. A flat headed nose on a bullet works very poorly. A Mk 108 round has a very large flat nose. (a .50 calibre round has a sharp streamlined nose) In addition, the shape of the rounds tail is important. A 'boat-tailed' round, or one which tapers to the rear, such as the .50 calibre will also retain its velocity much better than a round with a flat tail, such as the Mk 108. The shape of the Mk 108 round meant it would lose velocity very quickly. Which meant that gravitational acceleration would come even more into play. As the velocity of the Mk 108 drops off, it covers less distance, and gravitational acceleration drops the bullet path further downwards.

I don't have the time or patience to do the exact calculations for all these variables, but I suspect that the IL-2 model for gunnery does not take into account many of them. Which is why the Mk 108 is so effective in a fighter vs fighter role.