DCS Bf 109K-4

[OutOnTheOP]

Well, not exactly.

 

1st - Imagine you are shooting an actual M2 .50 on the ground, trying to hit something at some hundreds of meters;

2nd - Have a light barrel on that HMG which will decrease your accuracy but lighten the recoil (I think?);

3rd - Get you and the gun in movement;

4th - Get your target also moving;

5th - Add thick glass just infront you;

6th - Add the turbulence factor;

7th - Add a general slight shaking everywhere (engines, uneven air, etc.);

8th - Remember you are instructed to only shoot small bursts of 10-15 rounds per gun and have a certain cooldown time (it's stated in various manuals of the time, I'll try to find them);

9th - Even if one bullet hits, it's possible it wouldn't do that much damage, they are just HMG bullets after all, not cannons;

10th - Maybe more stuff I missed?

 

If it was that easy, they wouldn't really need escorts. :thumbup:

 

A lighter barrel has negligible effect on accuracy. For a 1000-meter precision rifle, sure. In the context of a machine gun, the heavier barrel is really only important as a heat sink, to prevent reaching cook-off temperature. In the M2 .50 cal, the entire barrel and trunnion reciprocates in the receiver; the "play" the barrel has to wiggle around will affect accuracy more than barrel heat (and recoil will affect it more than either). That said, keep in mind the guns ALSO have a sub-freezing, 200-mph wind blast to cool it. Overheating isn't a big issue here.

 

The "short bursts" bit is to prevent barrel overheating (again, not a major issue in this context), and to conserve ammunition. Mostly, that advice applies to ground-application .50 cal, where you carry far less ammunition (even tanks often carried only a couple hundred rounds), and where you may have to fight for a much longer period before resupplied (days, rather than the minutes or tens of minutes an air battle lasts). For a bomber, they can get a new gun barrel and plenty of ammo in a couple hours, when they land. The .50 is perfectly capable of firing 300-400 rounds in one long burst; I've seen it done. Now, the barrel will be glowing cherry red by the end of that, drooping slightly, and you'll strip the rifling right out of the barrel, but it will keep shooting that whole belt without jamming.

 

Of course, even if heating and ammo conservation WERE significant considerations for bombers, I think the gunner would have just laid on the trigger in this case: extra ammunition does no good to a dead man, and if there was ever a time it was worth shooting out the rifling of the barrel, that was it.

 

At that range, turbulence or not, it's hard to believe that the gunner would miss entirely. I really can't tell if he's firing or not; they don't produce THAT much muzzle signature. He could be firing, but didn't do enough damage... or could be firing at a second aircraft that was attacking with the one that. Or, it could just be that this was a particularly long air battle, and he was out of ammo. Kind of hard to tell.

 

As to needing escorts... that has more to do with breaking up coordination of attacks on the bombers than it does with any lack of lethality on the part of the bomber gunners. I seem to recall having read somewhere that more Luftwaffe pilots were shot down by bomber gunners than by allied fighters. I'd have to see if I can find the reference.

[OutOnTheOP]

Testing done by the USAAF found that the bullet pattern from a B-17 during ground testing had the following results for 12 rounds to 600yds:

 

tail turret > dia 45' - 25mils

 

Ok, but that's the 100% probability circle (and done with a mighty small sample!)... if I recall correctly, the 80% probability circle on weapon dispersion is about half the diameter of the 100%, which means 80% would hit a 22.5 foot diameter, or, in short, within 11 feet of the desired aimpoint. Even head-on, the fuselage is around 4.5-5 feet in diameter... so a hit rate of 10-30% is not out of line.... and that's at 600 yards.

 

Even assuming that the hits were EVENLY distributed in the circle (which isn't how projectile dispersion works), the area covered by a 45ft diameter circle is 1590 ft^2, while a 5ft diameter circle is 79 ft^2... which still equates to a 5% hit rate, even with the terribly unfavorable assumption of evenly-distributed rounds in that 45 ft diameter, and without considering any of the surface area of the wing or tail surfaces.

 

A mere 3-second burst from the paired AN/M2 would be 85 rounds.... even at 10%, that's 9 hits into the engine bay alone... at 600 yards. That attack wasn't even half that distance.

[Alicatt]

Well, not exactly.

 

 

2nd - Have a light barrel on that HMG which will decrease your accuracy but lighten the recoil (I think?);

 

A heavier barrel lessens the felt recoil, it is one of the reasons why match target rifles have a much heavier barrel, but not the only reason.

 

Carlos Hathcock, US Marine corps sniper, used a modified M2 as a sniper rifle, firing it in single shot with a locked breech, he made his longest kill at 2500 yds.

Edited November 4, 2014 by Alicatt

[MiloMorai]

I knew someone could put those numbers to use.

 

I don't know if those numbers are for the Cheyenne or the earlier mount. The Cheyenne should be better (had a reflector gunsight instead of the ring and bead of the previous installation).

[Kodoss]

There many similar videos with no return fire from the bomber. As Sith said, gunner incapacitated, for if he wasn't the attacking a/c would have been ripped to shreds at that distance and no cine film would have existed.

 

If I remember correctly gunners weren't allowed to fire within the bomber formation, because of hitting the friendly A/C. Also a possibility.

 

If the right inner engine is dead, the turrets wouldn't move either. That's what the pilots attacked at the first run from the front.

 

By the way shooting down a bomber with rockets wasn't greatly counted as kill. It was more used to open up the formation and then attacking the lone bomber, like a pack of wolves seperates and attacks the weakest prey within a herd.

Edited November 5, 2014 by Kodoss

[JST]

Semi-related; a lenghty attack on a B-17 by 110 G-2, 20mm mineshells mostly. There doesn't seem to be any return fire, the bomber is even flying solo:

 

http://www.youtube.com/watch?v=z6_NLhqjvBI&feature=youtu.be&t=1m57s

[fastfreddie]

If I remember correctly gunners weren't allowed to fire within the bomber formation, because of hitting the friendly A/C. Also a possibility.

 

If the right inner engine is dead, the turrets wouldn't move either. That's what the pilots attacked at the first run from the front.

 

By the way shooting down a bomber with rockets wasn't greatly counted as kill. It was more used to open up the formation and then attacking the lone bomber, like a pack of wolves seperates and attacks the weakest prey within a herd.

 

They fired at everything including friendly escorts if they thought they were attacking aircraft. Some German pilots reported that some bomber groups quit using tracer ammo but in this case the gunner was probably dead. Usually the first thing they shot at was the rear gunner and then the inboard engines. Experienced fight units attacked from the front but new, ground attack, or transferred units usually would dive down below and come up to attack from the bottom or rear.

[Kurfürst]

Ballistics table for MK 108 Minengeschoss, Type A. I believe there were other developments for the same ammo, with more pointed noses than the blunt nosed Ausf. A, which retained muzzle velocity much better, however I am not sure if these were developments only or were used in regular service as well.

 

Note that velocity will also effected by air density (altitude!) and aircraft speed (100-200 m/s is added to the speed of the projectile) as well.

[Solty]

Remember that your targets move with speed as well...so that factor goes out of the window :P

[tintifaxl]

Remember that your targets move with speed as well...so that factor goes out of the window :P

 

That depends on the direction: head on attack for the win!

[Kurfürst]

Remember that your targets move with speed as well...so that factor goes out of the window :P

 

Relative to the target, yes, but ballistics of the shell - no. A shell fired at 500 m/sec from a plane travelling at 200 m/sec will have a velocity of 700 m/sec, or so.

[Solty]

:thumbup:

[OutOnTheOP]

Ballistics table for MK 108 Minengeschoss, Type A. I believe there were other developments for the same ammo, with more pointed noses than the blunt nosed Ausf. A, which retained muzzle velocity much better, however I am not sure if these were developments only or were used in regular service as well.

 

Note that velocity will also effected by air density (altitude!) and aircraft speed (100-200 m/s is added to the speed of the projectile) as well.

 

Oh, wow, the ballistic coefficient is even WORSE than I had calculated it at... that's got to be something around 0.26-0.27 BC1. That's... not a whole lot better than a solid lead round ball in .50 caliber. Closure rate between projectile and target in a tail-chase would be mighty low. Better get close!

[fastfreddie]

Oh, wow, the ballistic coefficient is even WORSE than I had calculated it at... that's got to be something around 0.26-0.27 BC1. That's... not a whole lot better than a solid lead round ball in .50 caliber. Closure rate between projectile and target in a tail-chase would be mighty low. Better get close!

 

Well Kurfurst's document has the exit velocity at 500m/s, my book had it at 520m/s, and Wiki has it at 540m/s so there seems to be variations in data unless they improved the system some. What does Strich mean on the document?

[Tryhorn]

What does Strich mean on the document?

 

Maybe Strich stands for the Angle Unit.

I have found the followed informations on the german wikipage for Strich (Winkeleinheit).

There's a nautical Strich and a artillery Strich. The last one is also called mil.

I think the document is using the artillery Strich, which means they are using 6400 Strich for 360°.

Or for better conversion 1 Strich is 0,05625°.

 

I have no idea if this is the right unit, but it could be a first point of reference for your search.

[Friedrich-4B]

Although this deals with a modern 30mm cannon in a modern aircraft, it gives good info on common ballistic problems when flying combat aircraft; albeit against static ground targets.

(This will also be added to the A-10 manuals thread.)

 

Incidentally, are there any reports on the MK 108's effectiveness against ground targets?

[Kurfürst]

The GAU 8 is not really comparable to the MK 108, as its a radically different setup (multiple barrels, extremely powerful round and obscene rate of fire) which greatly contributes to that its accuracy (dispersion) is much worse at 5+ mils, as given by the report. Of course the GAU just literally obliterates any target with the sheer amount of rounds fired - it very much works like a huge shotgun firing #000 DU shots.

 

The MK 108 is, in contrast, a rather accurate weapons system (with dispersion ca. 1,5 mils IIRC) that fires fewer shells with much lower muzzle velocity and is meant for air targets. I suppose there is not much of a point firing its HE and Incendiary rounds at anything else than similarly flimsily built unarmored ground targets, though hitting a truck, an open topped half-track or gun position with the equivalent of 10 hand grenades per second sounds effective.

 

For everything else, there is MasterCard and/or the MK 103, a very different beast meant for the K-10 variant, despite the comparable ballistics performance GAU 8, with a dispersion of 2 mils but only about 1/10th of the rate of fire.

[Friedrich-4B]

The GAU 8 is not really comparable to the MK 108, as its a radically different setup (multiple barrels, extremely powerful round and obscene rate of fire) which greatly contributes to that its accuracy (dispersion) is much worse at 5+ mils, as given by the report. Of course the GAU just literally obliterates any target with the sheer amount of rounds fired - it very much works like a huge shotgun firing #000 DU shots.

 

My point in providing the report on the GAU8 is that it represents the types of problems involved in determining an aircraft weapon's ballistic capabilities during combat, as opposed to data gathered from ground-based test rigs or practice ranges, where targets don't fire back - it was never a direct comparison to the Mk 108.

 

The MK 108 is, in contrast, a rather accurate weapons system (with dispersion ca. 1,5 mils IIRC) that fires fewer shells with much lower muzzle velocity and is meant for air targets.

 

Is that 1.5 mil based on air combat statistics, or is it based on data gathered from test rigs on the ground? (Noting that the report on the GAU8 goes on to mention that the data gathered from combat showed that the dispersion in actual combat was greater than the test figures supplied by the aircraft and weapons manufacturers.)

 

Performance of aircraft system depends on system errors and target type,

manoeuvre of target, range and especially on air defense system intensity. System errors are error group such as ammo dispersion, gun pointing error, fire control prediction error, aircraft position, orientation, speed and acceleration errors, bore sight errors, target track errors, range errors, state estimate errors including time of flight error, body bending error, etc

 

At what ranges did the MK 108 achieve a theoretical 1.5 mil, and under what conditions?

[Der_Fred]

https://www.dropbox.com/s/t3s1mltu7lo80nc/DancingCloud.avi?dl=0

:)

[Kurfürst]

At what ranges did the MK 108 achieve a theoretical 1.5 mil, and under what conditions?

 

http://en.wikipedia.org/wiki/Angular_mil#Metric_Mil-dot_formula

[Yo-Yo]

Maybe Strich stands for the Angle Unit.

I have found the followed informations on the german wikipage for Strich (Winkeleinheit).

There's a nautical Strich and a artillery Strich. The last one is also called mil.

I think the document is using the artillery Strich, which means they are using 6400 Strich for 360°.

Or for better conversion 1 Strich is 0,05625°.

 

I have no idea if this is the right unit, but it could be a first point of reference for your search.

 

Looks like mils (there are several systems of artillery angle units based on different section of a 360 angle - 6000, 6200, 6400, maybe there are more systems). In this context, I think, it's an angle between the bore line and the point of impact.

[brooks143]

what is the release date on the 109?

[Highfox]

what is the release date on the 109?

 

Nov 2014.

I think I read somewhere it will be toward the end of the month (maybe I just made that up) !

 

Still I keep checking the forum every hour lol.

[NineLine]

Yup, no date has been give at this time, just that Nov is the target month.

[Viersbovsky]

Looks like mils (there are several systems of artillery angle units based on different section of a 360 angle - 6000, 6200, 6400, maybe there are more systems). In this context, I think, it's an angle between the bore line and the point of impact.

 

"Strich" means "line" or "dash" in German. Thus it think the addendum of the document refers to it:

 

"Conversion number for 1(dash) = 3.375' = 0.9875%0"

 

Maybe that helps clear things up.

 

edit: Yep, after some quick calculations it is Artelleristischer-Strich, or 0.05625° or roughly 1 mil. Theta 0 is simply the angle of the right triangle you get when drawing x and y as its legs.

Edited November 12, 2014 by Viersbovsky