MK 108 experts, please help!

[JunkyII]

Well the rudder could also have something to do with it....152 has a monster rudder which definitely helps making shots.

[Fulcrum]

Well the rudder could also have something to do with it....152 has a monster rudder which definitely helps making shots.

Agreed....and I use it quite a bit when making some shot situations.  K4 not so much.

[bustr]

Did some testing with the Ta152 and K4 MK108. I think HTC is modeling two different rounds based on the results. In truth the MK108 program probably has functions controlling rate of fire, velocity, and dispersion haptics which have been set slightly different. The IP points stay roughly the same for drop.

I performed three 5sec firing tests at 300 yards with both fighters to screen capture the target. Then counted round impacts offline and averaged them. Here are the rounds per minute results.

K4 ----- 492 rpm
Ta152 - 512 rpm

The National AF Museum figures for the MK108 are 487M\sec at 450rpm which was the figures for the early prototype. And there were two primary rounds used in the MK108. Both Minengeschoss but, one was cylindrical with a conical ogive that shot at 485M\sec while the second had a tapered ogive and shot at 500M\sec.

Dispersion testing showed the K4 patterns were wider than high while the Ta152 patterns were roughly equal in WxH.

I'm not sure how to test for the initial velocity with what is available to us in the game.  

Update:
At 500m with both planes it's taking just over 1sec to hit the target.

485m\sec will take about 1.3sec. from the book.
500m\sec will take about 1.15sec. from the book.

I don't have any way to tell the difference in .15sec. But, rate of fire is dependent on initial velocity.

[JunkyII]

I wouldn't be surprised if there may be a difference in the actual modeling of the guns.... I'd assume the characteristics of them shooting would be the same except with the position of the gun itself

[bustr]

Not really. In both engines the Mk108 is mounted into the rear end shooting through a pass through tube exiting the center of the spinner. The recoil is so low that neither plane should feel any effect. The only thing in real life that could effect the outcome of the trajectory would be the ogive of the round and a "slower or faster" initial velocity. During the life span of the gun type, the barrel length, number of groves and twist were never changed.

Recoil was controlled starting with the round was not fully seated when the primer was ignited. Most of the gasses then had escaped the barrel along with already pushing the bolt back which then was buffered with very heavy springs. So you ended up with a low velocity round and almost negligible recoil effect. The weight of the engine and the fact that the gun's action was behind the engine at the leading edge of the wing between the pilots feet should temper anything else. The ballistics were simply crappy because of the low velocity. At 860M\sec from the Mk103, the extra velocity and longer barrel improves the ballistics of the same round as you see in our Me410.

[Ardy123]

Remember that the velocity of the projectile is not just the speed of the projectile from rest but also must include the speed of the aircraft at the time of the shot..

example (k4 at 400 mph)
400mph = 178.816 m/sec
so 487 m/s + 178 = 665 m/sec

That also has an impact on the trajectory

[LCADolby]

My shooting is terrible at high speeds... Doesn't matter on the gun or projectile

[morfiend]

Not really. In both engines the Mk108 is mounted into the rear end shooting through a pass through tube exiting the center of the spinner. The recoil is so low that neither plane should feel any effect. The only thing in real life that could effect the outcome of the trajectory would be the ogive of the round and a "slower or faster" initial velocity. During the life span of the gun type, the barrel length, number of groves and twist were never changed.

Recoil was controlled starting with the round was not fully seated when the primer was ignited. Most of the gasses then had escaped the barrel along with already pushing the bolt back which then was buffered with very heavy springs. So you ended up with a low velocity round and almost negligible recoil effect. The weight of the engine and the fact that the gun's action was behind the engine at the leading edge of the wing between the pilots feet should temper anything else. The ballistics were simply crappy because of the low velocity. At 860M\sec from the Mk103, the extra velocity and longer barrel improves the ballistics of the same round as you see in our Me410.

  Bustr, the MK108 and Mk103 while both being 30mm they are not the same round! The shell casing on the Mk103 was much longer and held more propellent.


   But you knew that and just made a small error.





     

[bustr]

The ballistic trajectory profile is a result of the relationship between the round at initV in the chamber and it's travel down the barrel along with the barrel's relative relationship to gravity at the moment the round leaves the barrel. At an initial PSI that results in 500 M\sec at the exit of the 23 inch 30mm barrel with 1:16 twist. You have crappy dispersion that kills the round's effectiveness as a fighter to fighter gun in a single gun mounting. The added momentum from the plane's speed just means the round reaches it's crappy dispersion that much quicker. But, it is a negligible part of the overall components creating the trajectory profile. With a slow speed round with crappy ballistics, high aircraft speeds will tend to influence badly your ability to hit things unless you are traveling in a straight line.

Now if the velocity exiting the muzzle was 665 M\sec you would have a slightly better long range trajectory and dispersion past 100m. But, then you would have the recoil problems associated with the larger amount of propellant and probably a need for a slightly longer barrel. Then it would probably be too much for the small airframe of a 109 along with a weight increase overall of the gun so the action could survive the pounding. The original reason for the light weight low recoil of the Mk108 design with crappy ballistics. Or why you didn't see MK103 in gondolas mounted to 109's.

The MK108 ballistic profile in the game today, doesn't seem to be as friendly as it was 3 to 5 years ago. I no longer hear many players talking about making 400-600 yard kill shots as a standard with the tater anymore like they did back then. Players today seem to talk more about getting closer to achieve kill shots with the K4 and Ta152 against fighters.

Morph,

Mk103\Mk108 used the same round, different cases.

Mk103\108
Round\projectile  =   3 cm M-Gesch. 108 Ausf.A m. Zerl.\3 cm M-Gesch. L.spur m. Zerl. / 3 cm M-Gesch. .Gl.spur m. Zerl.

Mk103 Case\Shell -  30x184B 860M\sec
Mk108 Case\Shell -  30×90RB 500M\sec

[morfiend]

 



   

[Ardy123]

The ballistic trajectory profile is a result of the relationship between the round at initV in the chamber and it's travel down the barrel along with the barrel's relative relationship to gravity at the moment the round leaves the barrel. At an initial PSI that results in 500 M\sec at the exit of the 23 inch 30mm barrel with 1:16 twist. You have crappy dispersion that kills the round's effectiveness as a fighter to fighter gun in a single gun mounting. The added momentum from the plane's speed just means the round reaches it's crappy dispersion that much quicker. But, it is a negligible part of the overall components creating the trajectory profile. With a slow speed round with crappy ballistics, high aircraft speeds will tend to influence badly your ability to hit things unless you are traveling in a straight line.

Yeah, I don't know what I was thinking, I was never saying that it would impact the dispersion but that it would impact the curve of the trajectory and that doesn't even make sense because the shooter isn't suddenly going to a velocity of 0 after the projectile leaving the chamber. But dispersion being the real problem.. its kinda irrelevant.