Question about the 20mm cannon modeling

[vossiewulf]

I'm new to this game, but have been around WWII aviation and other sims a long time.

 

If my first hours, I was testing the La-5FN, the Bf-109G-2/G-4 and the Spitfire M.V. The thing I found odd is the shVAK acts to my eyes almost like a 37mm blooper gun, the MG-151/20 of the 109 isn't much better; even from close ranges, in tight turns the bad guy had to be completely beneath the nose to hit.

 

Then we come to the Hispano, which is a wonder weapon. Muzzle velocity much higher than either of the previous two, bad guys can be in view and you're watching the hits in the same tight turns that required the bad guys to be below the nose (109) or practically behind the shooter with the shVAK.

 

And the reason that doesn't make sense to me is that the muzzle velocity of the Hispano is ~880m/s, the MG-151/20 is ~850m/s, and the shVAK isn't terrible at ~750-780m/s. There shouldn't be much difference in the trajectory of the first two inside 300m, and the shVAK would only drop a little in that distance. Instead the velocities I see look more like a Hispano vs. MG-FFs or maybe the MiG-15's 37mm.

 

Note I'm not assuming this is the first time this has been discussed, the game has been around a while. So what I guess I'm looking for is what the current explanation from 1C is for this oddity.

[the_emperor]

Hey there,
the Hispano MkV fires a 131g projectile at 850m/s with a improved pointed nose fuse (for better ballistics) with 47323Joule
The Mg151/20 fires a 92g Mineshell at 790ms/ with 28708 Joules
and a 115g SAPI or HE-I Tracer at 705m/s (some sources state 720m/s) with 28578 Joules.
For the Shvak I just have Wikipedia as a reference:
A 91g HEI- Round at 790ms  with 28396 Joules.
and a 96g Round at 760 27724 Joules.
The Shvak and Mg151/20 should have similar ballistics while the Hispano surpasses both due to higher velocity at more weight and pointed fuse instead of a blunt travelling the 1000yards at 1.66 seconds.

Cheers

Edited March 18, 2020 by the_emperor

[vossiewulf]

Thanks TE, ok, those numbers are a bit different but not totally out of line with mine. To be clear, my testing was gunnery right around 100m or a bit less, in 3G-5G turns. At those distances, the difference in the trajectory of the MG151/20 and the Hispano is going to be inches at most even with your numbers, with the shVak maybe a foot below.

 

Out at 250m+ yes you'd start to see significant differences. But the difference in aiming points I'm using for these tests are really different for the three guns, with the Hispano rounds dropping just a bit, as I said it's the only one where I can see the rounds hit. With the other two I kept missing and had to record some sessions and go back and walk through them to see wow, I'm still way behind guys when the same shots with the Hispano rapidly disassemble a whole plane. These seem to me more like 800m/s, 600m/s and maybe 500m/s for the shVAK.

 

Don't get me wrong, I'm enjoying the game, but every game has a million assumptions in their modeling and a great game can still have a few wacky things.

 

In fact I laughed for quite a bit this evening, it was my first mission in the scripted fortress on the Volga after the ferry flight mission, had one kill already and had good hits on the wing root of a Yak-1b, The pilot was working hard, took me a while to reel him back in, and then he did one of the neg-G push evasives followed by snapping into a high pos G turn, his wing folded- some two minutes after I'd hit him. That was totally awesome that the damage model weakened the spar and when he went for 6Gs for the third or fourth time after taking hits, it failed. Those kind of things really do wonders for the suspension of disbelief.

 

Also I'm playing with an HP Vive, and the immersion of VR is amazing. I have a TrackIR 5 but I don't see myself using it much moving forward.

Edited March 18, 2020 by vossiewulf

[Yogiflight]

The main reason, I think is, the MG151/20 in the 109s and the ShVaK in the La-5FN are nose mounted, which means they are directed straight, parallel to the engine (at least the in 109, not completely sure about the La-5FN), while the guns of the Spitfire are wing mounted and therefore directed upwards, like the wing profiles.

[cardboard_killer]

I wonder if convergence could also be affecting the issue. If you set your convergence close, there will be little arcing of the rounds, but if you set it out to 500 meters the nose canon will travel a few feet upward once fired. Even more so with wing mounted guns.

 

I've seen a lot of good Il-2 pilot videos where the convergence is set pretty far ahead, much farther than I understand to have been the case for higher kill pilots historically from my readings. Is this a case of setting a long range convergence in order to get high arc against high deflection shot, close range targets?

[Yogiflight]

4 minutes ago, cardboard_killer said:

I wonder if convergence could also be affecting the issue. If you set your convergence close, there will be little arcing of the rounds, but if you set it out to 500 meters the nose canon will travel a few feet upward once fired. Even more so with wing mounted guns.

 

I can only really speak for the 109. The trajectory of the engine gun was not changed through convergence settings, as it was fix mounted, you could not move it. Don't forget, it was mounted with the housing behind the engine, shooting through a small tube in front of the engine. What was adjusted by setting the convergence, was the upper glas of the gunsight, so the view of the pilot did cross the trajectory of the bullets in 400m. So the pilot did not look straight ahead, while aiming, but a bit down. Only the machineguns above the engine were adjusted, so their bullets crossed the trajectory of the 20mm gun in 400m.

[cardboard_killer]

But is that true in the game as well as historically? Seems like a silly question, but no game is perfect, and I could understand that being missed.

[Yogiflight]

2 minutes ago, cardboard_killer said:

But is that true in the game as well as historically?

Good question. I have no idea.

[vossiewulf]

39 minutes ago, Yogiflight said:

The main reason, I think is, the MG151/20 in the 109s and the ShVaK in the La-5FN are nose mounted, which means they are directed straight, parallel to the engine (at least the in 109, not completely sure about the La-5FN), while the guns of the Spitfire are wing mounted and therefore directed upwards, like the wing profiles.

 

That's a good point.

[cardboard_killer]

From the 1C website:

 

[AlphaHasen]

 

Convergece BF-109 F1 with MG/FF.

 

More Infos https://www.deutscheluftwaffe.com/archiv/Dokumente/ABC/m/Messerschmitt/Me 109 / Bf 109 F1 Bedienung der Schusswaffe.pdf

Edited March 18, 2020 by JG4_RuckZuck

[Yogiflight]

2 hours ago, cardboard_killer said:

From the 1C website:

 

Note, this one is from the FW190 A8, with the MG131 machineguns vertically adjusted to 400m and the and the MG151/20 adjusted to 550m. In the Focke Wulf the guns were adjusted, not the gunsight.

BTW, this is no official 1C drawing, but from the Cliffs of Dover forum

It would be nice if the convergence of 700m for the gondola guns would be implemented, together with a default convergence setting, like it was IRL.

Edited March 18, 2020 by Yogiflight

[vossiewulf]

Here's the P-47 harmonization instructions, since there is a nice list of them here.

 

However, nice as they all are, I have no idea how if the fire of any of the aircraft match these.

 

[unreasonable]

4 hours ago, cardboard_killer said:

But is that true in the game as well as historically? Seems like a silly question, but no game is perfect, and I could understand that being missed.

 

In the game F4 the position of the gunsight is unchanged when convergence is altered, the flight of the shells is changed, ie at 100m convergence the 20mm trajectory goes up and through the reticule spot at 100m going well above it before dropping back down. At 1000m it stays low and just reaches the spot at 1000m

 

Easiest way to see this is to fire the cannon from a plane on the runway in QMB or the ME using a fixed camera position and overlay screenshots.  Actually if the OP wants to compare ballistics, this is also the best way: far too many variables in his original example to determine.   

[RedKestrel]

1 hour ago, vossiewulf said:

Here's the P-47 harmonization instructions, since there is a nice list of them here.

 

However, nice as they all are, I have no idea how if the fire of any of the aircraft match these.

 

No, in-game all wing-mounted guns fire to a point convergence, they don't produce a pattern like you see here. So they will hit harder at convergence but its a little harder to hit at different ranges.

[Jason_Williams]

I wouldn't focus on our DM or ammo right now because it's all being updated soon with our improved DM discussed on our recent DD. Don't stress about this kind of stuff right now.

 

Jason

[Feathered_IV]

Just buy FC.  Close to within 8 metres of your target and shoot.  

[vossiewulf]

9 hours ago, Jason_Williams said:

I wouldn't focus on our DM or ammo right now because it's all being updated soon with our improved DM discussed on our recent DD. Don't stress about this kind of stuff right now.

 

Jason

 

That's good to hear, but I don't have enough experience to complain about the damage model  My question was about muzzle velocities and therefore aiming points, are you updating the muzzle velocities of the weapons as well?

 

3 hours ago, Feathered_IV said:

Just buy FC.  Close to within 8 metres of your target and shoot.  

 

There's a problem here but at the same time, I've never seen any game do differently. What I mean is it's clear the enemy AI always knows when you close within shooting range.

 

You can read, well, everything about WWII aviation victories and you hear over and over that they rolled into a formation and nobody saw them. Hartmann in particular talks about flying right up to 10m away from Soviet plane after Soviet plane and shooting them down with them having no idea he was there.

 

Here, you can't do that, and that's a very large section of actual combat realism that's missing.

 

The one that bothers me a bit more, and I've seen it in many games, is the AI knows not only that you're in firing range but exactly where you're aiming and it will react to the pipper being moved to a spot that will hit them. Another way you can see this is the AI will over and over again know exactly where to fly to put themselves directly between you and the sun. Not approximately, but exactly.

 

I understand these features exist to make the game more challenging, but honestly I would rather have realism with the option of enabling features like that if I wanted to unrealistically inflate the challenge. So I hope they can make those kinds of things toggleable in difficulty options.

 

Edited March 19, 2020 by vossiewulf

[Jade_Monkey]

18 hours ago, vossiewulf said:

The one that bothers me a bit more, and I've seen it in many games, is the AI knows not only that you're in firing range but exactly where you're aiming and it will react to the pipper being moved to a spot that will hit them. Another way you can see this is the AI will over and over again know exactly where to fly to put themselves directly between you and the sun. Not approximately, but exactly

 

I'm pretty sure that's is not part of the AI routine and you just had it happen a few times and it really stuck with you. I'm not arguing about the AI know you are coming into them but the sun part is just not true.

[vossiewulf]

51 minutes ago, Jade_Monkey said:

 

I'm pretty sure that's is not part of the AI routine and you just had it happen a few times and it really stuck with you. I'm not arguing about the AI know you are coming into them but the sun part is just not true.

 

I defer to someone who has like a zillion more hours than me.