Author Topic: Lazy 30mm question  (Read 4076 times)

Offline Spork

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Re: Lazy 30mm question
« Reply #15 on: January 16, 2011, 09:57:09 PM »
My point isn't that convergence matters much with nose-mounted guns.  It doesn't.  There are ways to adjust it to "make it" matter more than it should, one of which is to stretch it way out.  A handicap of sorts, willingly applied.

The timing aspect though, still plays out, and gets worse the further out you fire (simply because range estimation, and estimation of projectile travel time gets more difficult).  I've never looked at the specs for any gun on any German plane, so I'll just take your word for the 6.5 rounds per second rate of fire.  A gun firing at 6.5 rounds per second is firing one round every .1538 seconds.  By my math, a plane crossing in front of you at 250mph is moving at 340 FPS, which means it travels 53.2 feet in the time between rounds leaving the barrel.  An F4U is a pretty large fighter (at 33ft 4" length), and 250 is not too fast when it comes to an estimate of speed.  Plenty short to squeeze (albeit unintentionally) into a 53ft space.

That basically means that in a 90 degree crossing shot at a 250mph target, only one round really stands a chance of hitting it.  The round fired before will pass in front, the round after will pass behind.  That "golden" round, fired at roughly the right time, and aimed perfectly, stands about a 62% chance of hitting.  If the trigger squeeze is off by .09 seconds though, it's a miss.  If you're "off" by more than .09 seconds, your next perfectly-aimed round would be the one to stand a 62% of scoring a hit.  Odds of a hit would be worse if the target was a smaller plane, or was crossing at a higher speed, and would drop to zero if it wasn't aimed perfectly.

Of course, there are ways to improve your odds.  As you mention, getting close will help, as will reducing the crossing angle and/or speed.  Setting up a situation where you can hold (and adjust) a sustained lead would be even better.

And of course, setting up a sustained lead would totally blow any importance the convergence setting has, especially with nose-mounted guns.


You just negated all of your "math" with that statement.



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Offline mtnman

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Re: Lazy 30mm question
« Reply #16 on: January 17, 2011, 05:16:59 AM »

You just negated all of your "math" with that statement.



Spork

Nope.  But it appears that you don't comprehend the rest.  Try harder.   

It doesn't matter to me what the rate of fire is exactly; I'm quite willing to use Grizz's knowledge of that.

Figure the math out on your own.  Show me where it's wrong.  Show me how the math shown is negated, by not looking up a spec on a gun.
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Offline Spork

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Re: Lazy 30mm question
« Reply #17 on: January 17, 2011, 11:35:40 AM »
Nope.  But it appears that you don't comprehend the rest.  Try harder.   

It doesn't matter to me what the rate of fire is exactly; I'm quite willing to use Grizz's knowledge of that.

Figure the math out on your own.  Show me where it's wrong.  Show me how the math shown is negated, by not looking up a spec on a gun.

 :aok
Ignorance is bliss isn't it?


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Offline mtnman

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Re: Lazy 30mm question
« Reply #18 on: January 17, 2011, 07:59:28 PM »
:aok
Ignorance is bliss isn't it?


Spork


Ha!  You're so coy!

The math is correct, based on the information (and example) given.

Are you saying that Grizz's RoF estimate is wrong?  Maybe I'll look it up, if I get time.

Are you able to contribute anything?

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Offline grizz441

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Re: Lazy 30mm question
« Reply #19 on: January 17, 2011, 08:12:52 PM »
Ha!  You're so coy!

The math is correct, based on the information (and example) given.

Are you saying that Grizz's RoF estimate is wrong?  Maybe I'll look it up, if I get time.

Are you able to contribute anything?



My number came from in game test, actually Sunbat tested it and told me what he recorded.   Calculating the time it takes to fire all 65 taters off.  I trust his means.  It might be slightly off but not really a significant amount for all intents and purposes.  I agree that a plane can squeeze through a pure 90 degree deflection shot, I trust your math MtnMan.  However, most angles are not pure 90 degree crosses which makes it much more difficult to squeeze through.  A properly set up, aimed, and placed stream of taters will destroy the aircraft 90%+ of the time.
« Last Edit: January 17, 2011, 08:14:28 PM by grizz441 »

Offline Gooss

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Re: Lazy 30mm question
« Reply #20 on: January 17, 2011, 08:20:24 PM »
:aok
Ignorance is bliss isn't it?

You are the proof.   :rofl
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Offline Spork

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Re: Lazy 30mm question
« Reply #21 on: January 17, 2011, 08:56:28 PM »
My point isn't that convergence matters much with nose-mounted guns.  It doesn't.  There are ways to adjust it to "make it" matter more than it should, one of which is to stretch it way out.  A handicap of sorts, willingly applied.

The timing aspect though, still plays out, and gets worse the further out you fire (simply because range estimation, and estimation of projectile travel time gets more difficult).  I've never looked at the specs for any gun on any German plane, so I'll just take your word for the 6.5 rounds per second rate of fire.  A gun firing at 6.5 rounds per second is firing one round every .1538 seconds.  By my math, a plane crossing in front of you at 250mph is moving at 340 FPS, which means it travels 53.2 feet in the time between rounds leaving the barrel.  An F4U is a pretty large fighter (at 33ft 4" length), and 250 is not too fast when it comes to an estimate of speed.  Plenty short to squeeze (albeit unintentionally) into a 53ft space.

That basically means that in a 90 degree crossing shot at a 250mph target, only one round really stands a chance of hitting it.  The round fired before will pass in front, the round after will pass behind.  That "golden" round, fired at roughly the right time, and aimed perfectly, stands about a 62% chance of hitting.  If the trigger squeeze is off by .09 seconds though, it's a miss.  If you're "off" by more than .09 seconds, your next perfectly-aimed round would be the one to stand a 62% of scoring a hit.  Odds of a hit would be worse if the target was a smaller plane, or was crossing at a higher speed, and would drop to zero if it wasn't aimed perfectly.

Of course, there are ways to improve your odds.  As you mention, getting close will help, as will reducing the crossing angle and/or speed.  Setting up a situation where you can hold (and adjust) a sustained lead would be even better.

And of course, setting up a sustained lead would totally blow any importance the convergence setting has, especially with nose-mounted guns.

If you don't see why your "62% of scoring a hit" is wrong, then I am not going to sit here and explain it to you. However, I guess to be fair, if you did know that it was wrong you wouldn't have posted it in the first place so  :rock sir



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Offline Spork

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Re: Lazy 30mm question
« Reply #22 on: January 17, 2011, 09:09:55 PM »
My point isn't that convergence matters much with nose-mounted guns.  It doesn't.  There are ways to adjust it to "make it" matter more than it should, one of which is to stretch it way out.  A handicap of sorts, willingly applied.

The timing aspect though, still plays out, and gets worse the further out you fire (simply because range estimation, and estimation of projectile travel time gets more difficult).  I've never looked at the specs for any gun on any German plane, so I'll just take your word for the 6.5 rounds per second rate of fire.  A gun firing at 6.5 rounds per second is firing one round every .1538 seconds.  By my math, a plane crossing in front of you at 250mph is moving at 340 FPS, which means it travels 53.2 feet in the time between rounds leaving the barrel.  An F4U is a pretty large fighter (at 33ft 4" length), and 250 is not too fast when it comes to an estimate of speed.  Plenty short to squeeze (albeit unintentionally) into a 53ft space.

That basically means that in a 90 degree crossing shot at a 250mph target, only one round really stands a chance of hitting it.  The round fired before will pass in front, the round after will pass behind.  That "golden" round, fired at roughly the right time, and aimed perfectly, stands about a 62% chance of hitting.  If the trigger squeeze is off by .09 seconds though, it's a miss.  If you're "off" by more than .09 seconds, your next perfectly-aimed round would be the one to stand a 62% of scoring a hit.  Odds of a hit would be worse if the target was a smaller plane, or was crossing at a higher speed, and would drop to zero if it wasn't aimed perfectly.

Of course, there are ways to improve your odds.  As you mention, getting close will help, as will reducing the crossing angle and/or speed.  Setting up a situation where you can hold (and adjust) a sustained lead would be even better.

And of course, setting up a sustained lead would totally blow any importance the convergence setting has, especially with nose-mounted guns.

Alright, I'll stop being a dick and explain why your math for the "golden round" is wrong.

There are several different factors that you did not account for in your example throwing your math off, which in turn negates it. When I first posted the "I've never looked at the specs for any gun on any German plane" statement negated all your math it is because of this:

Your rounds between firing is correct, but that is the only thing you got correct. When you fire a round that round has a velocity. It is that velocity that determines "when" the round impacts not only how fast the target is crossing you. That means Round Velocity plays an integral part of the equation, no? And when you said " I've never looked at the specs for any gun on any German plane" that means you do not know the round velocity. Without which, your calculation is completely inaccurate.

Another part of your equation that you failed to mention or calculate for, is your own plane's velocity. You are traveling forward as well are you not? Airplanes can't hover, obviously, so yes you are. You also will need to take that into account (your forward velocity) when you are calculating when a "hit" will occur because you have a "closure rate" between the two aircraft which, in turn, decreases the distance between the two targets for every round that is fired.

Round diameter (if it impacts/where it impacts/how much of the explosion reaches and effects the target), constantly changing angles vs. the two points of reference(you vs. your target) etc.

All of that would will need to be calculated for to get your "golden round %"

Make sense?


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Offline Owlblink

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Re: Lazy 30mm question
« Reply #23 on: January 17, 2011, 09:49:14 PM »
Well, Spork is correct on many points, however mtnman states to assume a 90 degree angle-off-tail for the cross shot, so that is a constant not a variable.

Also, like every statistical calculation, there is no such thing as 100% accuracy. You cannot, in life, account for every single aspect. Everything works within a system of events, nothing is singular or linear even though it can sometimes appear that way. You could, for instance, even consider the engine torque to play a role in the equation as well, but that is often overlooked because the "preciseness" doesn't matter in the end, just a common 95% level of confidence

That being said, we're getting off topic, but when stating numbers it's best to show your calculations. Even if your average troll doesn't follow it, someone else will, and you can't argue with numbers presented in fact.

Very nice thread, I've been given a bit more insight into the art of tater smashing. Keep up the help full work  :salute
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Offline grizz441

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Re: Lazy 30mm question
« Reply #24 on: January 17, 2011, 09:57:15 PM »
Actually, in MtnMan's example, round velocity is completely irrelevant.  I should probably let you figure it out for yourself as to why you are so terribly wrong, but since I don't think you are capable, I will explain it to you.  If you fire projectiles at a certain rate per second all at the same velocity, it is irrelevant at what velocity they are firing at.  The gap between the bullets will not change, as the gaps are only a function of the firing rate.  If you shot bowling balls out of your aircraft at 6.5 bowling balls per second at 10mph, the gaps would be equal to the gaps created by a machine gun with the same firing rate.  All round velocity matters for is lead, which has nothing to do with a plane sneaking through the rounds.  MtnMan was correct, you are wrong.

Make sense?

Edit:
The gaps would be different based on different speeds, I mistyped that sentence in red, however the probability of getting hit would be equivalent based on small gaps, small velocity versus large gaps large velocity.
« Last Edit: January 17, 2011, 10:41:12 PM by grizz441 »

Offline mtnman

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Re: Lazy 30mm question
« Reply #25 on: January 17, 2011, 10:03:21 PM »
Alright, I'll stop being a dick and explain why your math for the "golden round" is wrong.

There are several different factors that you did not account for in your example throwing your math off, which in turn negates it. When I first posted the "I've never looked at the specs for any gun on any German plane" statement negated all your math it is because of this:

Your rounds between firing is correct, but that is the only thing you got correct. When you fire a round that round has a velocity. It is that velocity that determines "when" the round impacts not only how fast the target is crossing you. That means Round Velocity plays an integral part of the equation, no? And when you said " I've never looked at the specs for any gun on any German plane" that means you do not know the round velocity. Without which, your calculation is completely inaccurate.

Another part of your equation that you failed to mention or calculate for, is your own plane's velocity. You are traveling forward as well are you not? Airplanes can't hover, obviously, so yes you are. You also will need to take that into account (your forward velocity) when you are calculating when a "hit" will occur because you have a "closure rate" between the two aircraft which, in turn, decreases the distance between the two targets for every round that is fired.

Round diameter (if it impacts/where it impacts/how much of the explosion reaches and effects the target), constantly changing angles vs. the two points of reference(you vs. your target) etc.

All of that would will need to be calculated for to get your "golden round %"

Make sense?


Spork

Yup, makes sense, but it's a common misconception.  

The velocity of the round doesn't factor into the "time between the spaces", so to speak.  It factors into the timing in how far ahead (in time and or distance, depending on how you want to look at it) of the target you'd need to aim.  The distance the target will travel between the time the rounds are fired is the same regardless of the velocity of the round.  The round could go ten times as fast as it does, but the target would still travel the same distance in the time between each round leaving the bore (if the RoF is the same).  I can elaborate more tomorrow night if need be, but if you think it through I think you'll see it.

It's a rate of fire question, not a velocity question.  Velocity would effect how much lead is required, it wouldn't effect how far the target moves between round 1 being fired, and round 2 being fired.

I didn't factor the forward progress of the 109 in, because it's really fairly negligible compared to the speed of the round.  It really only makes a difference of a few percent generally.  And again, it doesn't effect the distance the target travels between the time the rounds are fired.  As proof, think of it like this- if you fire at a plane crossing in front of you at xxx mph, the target will travel xxx feet every x seconds.  Now, fire your guns forward while that plane crosses behind you...  How far does he travel in the time between the rounds being fired?  The same distance as he would if he was in front of you, or beside you, or under you... 


The other reason I didn't factor in a whole multitude of things into the equation is that almost all of them reduce the likelihood of a hit.  There are really only a few things you can do to improve your chances of a hit, whereas there are a whole lot of things that make your chances worse.  In reality, the stationary, "rock-solid" firing platform, vs the pure 90 degree crossing shot on a known-speed, known-size, and known-distance target is as good as it gets.  Forward motion of your plane also has negative connotations when it comes to aiming, especially in a situation where closure is high, and required lead is great.  It'll reduce your chances of a hit almost invariably, because it makes estimation (which ties to lead calculation) more difficult.  Your first shot fired is the generally your best-aimed shot.  When it fails, and you need to re-adjust, you'll now have less time and a different set of variables to contend with.  Of course, the target is a little bigger...


Look at the 62% estimate, and then consider the arguments (although I agree that they do have merit).  The argument seems to be that 62% isn't a high enough probability of a hit?  In reality, how high is the probability of a hit by any 30mm round fired?  62% is ridiculously high...  If the best 109 pilot in the game counts his 30mm hits for a week or a month, or whatever, what % will be hits?  Is anyone holding a 62% hit% with the 30mm's?  Why not?
« Last Edit: January 17, 2011, 10:13:59 PM by mtnman »
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Offline moot

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Re: Lazy 30mm question
« Reply #26 on: January 17, 2011, 10:15:10 PM »
Grizz it does matter what speed they're flying at. That and the rate of fire decide how large the gaps are between each round, and how fast a target needs to be flying relative to the bullet stream to slip thru those gaps untouched.

If you're firing more than one round, it probably means you aren't near 100% sure of your aim & timing, so right away hitting's up to chance, ie probability.  Rate of fire then matters if the gun's ROF is low enough that the target could fly thru the stream, e.g. 2 taters fired just so the first passes in front of target nose and the second right behind its tail.

The gaps are a function of both firing rate and relative speeds.  Imagine running thru rain: with rain pouring down normally, then with rain stopped (like running thru one of those Matrix scenes where time's stopped), then with rain pouring down at near infinite speed. And all three again with varying raindrop density. Each one gives you different probabilities of getting wet / running around the raindrops without getting wet.

More on topic - changing convergence on a low velocity round like the MK108 can really get in the way of a low/medium experience player when you shoot at very high speed.  You can see this easily if you take a 262 offline and shoot long bursts of all guns at 550mph+.  Do it once with short convergence, then again with long convergence.  At high speed, the rounds will travel much further (since their velocity isn't just muzzle velocity but MV + the plane's very high speed) before bending back down.
And then it's even less intuitive when you shoot near vertical angles, or inverted.


Mtnman - 62% meaning chance the pilot aimed and timed on target, or 62% chance a perfectly aimed/timed shot will hit due to dispersion?
« Last Edit: January 17, 2011, 10:18:30 PM by moot »
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Offline The Fugitive

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Re: Lazy 30mm question
« Reply #27 on: January 17, 2011, 10:19:16 PM »
ummmmmm shall we say "schooled"   :D

Well posted, and explained gentlemen.

Offline grizz441

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Re: Lazy 30mm question
« Reply #28 on: January 17, 2011, 10:19:43 PM »
Grizz it does matter what speed they're flying at. That and the rate of fire decide how large the gaps are between each round, and how fast a target needs to be flying relative to the bullet stream to slip thru those gaps untouched.


I don't think so dude.  The size of the gaps are proportional to the velocity.  The two factors effectively cancel one another out.  If you fired bowling balls at 10 per second, their velocity would be incredibly low but their gap would be very tight.  If you fired 50 cals at 10 per second, the velocity would be incredibly high but their gap would be very wide.  The two are linearly proportional.  Ultimately, the only thing velocity affects is lead.

As for your matrix example, that would be a function of your target's speed, not the speed of the bullets.  In other words, a target with X velocity has the same probability of squeezing through a stream of 2 bullets spaced z feet apart traveling y mph as he would 2 bullets spaced 2*z feet apart traveling at 2*y mph.

Edit: We are saying the same thing.  I misconstrued what I was trying to say in my initial post.  In a nutshell, all that matters is the rate of fire.
« Last Edit: January 17, 2011, 10:44:08 PM by grizz441 »

Offline Muzzy

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Re: Lazy 30mm question
« Reply #29 on: January 17, 2011, 10:19:51 PM »
I got a golden bullet today....got a kill with the tater at -400....so, like, it's possible, right?

Okay I'm leaving again.  :bolt:


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