P-38 Convergence

[Ratpack1]

It was the original one yes.

[warhed]

I find that I have no trouble getting bullets to converge on my 38.   

That was your question right?

Your self-deprecation is so underappreciated 

[Cajunn]

Every plane I fly, cannons 275, MG's 250

[hlbly]

One thing I want to point out is this . what delirium <I think> is also doing that he didn't explain is this , by putting his 20mm 50 farther out than his .50's . He makesthe cannon and mg's hit much closer together . Due to differences in muzzle velocity and other factors placing the 20 mm this way they hit much closer together then if they are set at the same range . Go to TA and check the difference by using the friendly lock . It will clearly show the 2 x's much closer together .

[DamnedRen]

I normally shoot inside 200. I set my guns to 200. If I can all my shots are made from nose to tail or wing root to wing root.
That way I don't pass through the parts and risk damaging my ride.

I do this with all my rides. I have a notch on my vertical line above the pipper which lets me ping out to 800 just to wake the guy up. He shouldn't be asleep when he turns and takes one for the gipper.

If you notice it is not a convergence set up for any type of HO. I don't teach that nor do I do it (unless I just wanna p the guy off ). There are lots of other folks that can do that.

Ren
Aces High Training Corps

[mtnman]

One thing I want to point out is this . what delirium <I think> is also doing that he didn't explain is this , by putting his 20mm 50 farther out than his .50's . He makesthe cannon and mg's hit much closer together . Due to differences in muzzle velocity and other factors placing the 20 mm this way they hit much closer together then if they are set at the same range . Go to TA and check the difference by using the friendly lock . It will clearly show the 2 x's much closer together .

It's funny I guess, but it shouldn't work that way...

If the cannon rounds fly slower than the MG's, they'll tend to fly a path with a more exagerated arch.  And the MG's would fly "straighter".  If that's the case, then the cannon rounds will fly a path ABOVE the path the bullets fly, and won't drop down to the level of the bullets until they hit the set convergence distance...  

Setting the cannon to converge at a point further away than the MG's should exagerate that difference even more...  Causing the cannon rounds to fly a path even higher than they normally would, or even further outside the flight-path of the MG rounds...

Conversely, setting the cannon rounds to hit at a distance slightly closer than the MG should be a better compromise...  This should cause the cannon rounds to fly a path that isn't as high above the MG's flight path through the course of the flight, and hit slightly below the MG rounds.  

Assuming the cannon rounds flew an arch that was 1 foot more vertically pronounced than the MG's, setting the cannons to hit closer would cause the cannon rounds to fly only 6 inches above the MG's at their highest point, and hit 6 inches low at the target distance...  Whereas setting the cannons to hit further out may cause the cannon rounds to fly a path as much as 1.5 feet above the flightpath of the MG rounds...

Sounds backwards maybe, but if you stop to think about the flightpaths for a minute...  I suppose I could draw a diagram...

Of course, I'm not positive (although I do suspect) that the MG's fly a "flatter" trajectory anyway.  If the MG's actually fly a more pronounced arch than the cannon rounds, then setting the cannons to hit further out may be the correct option.

And of course, setting the MG's and cannons to hit at a certain point is really only going to matter on a target that appears stationary, because the cannon rounds and MG rounds may all hit a certain point, but they won't do it at the same time.  On a crossing target, that would require a differing amount of lead for the cannons vs the MG's.  If you lead enough for the faster-flying rounds, your slower flying rounds will pass behind the target.  Lead a bit extra for the slower rounds, and the faster rounds will have too much lead, and pass in front of the target.  

Toss in a different rate of fire for the guns and things could start getting a bit complicated, hehe!

Of course, a 25yd difference between the two convergences probably doesn't make more than an inch of difference anyway...

Ballistics is fun.

[hlbly]

I never thought it out but I see your point . So I went into the TA to check . The green crosses are closer together with the 20mm 50 farther out . I reread your post mountain . I think you have the right of it . After I got a pen and paper and sketched it out I agree. However the 2 X's when u enable friendly lock say otherwise . That being said , is it a bug ? Wouldn't the fact that the X's are closer together mean you are landing more concentrated bursts on you target moving or other wise ?

[mtnman]

Good questions, and I can't say that I know...  I've never played with the nose-mounted guns in the TA.

One thing I've noticed in the TA is that the little green x doesn't always go where the bullets go...  It's not quite a "perfect" tool.  Rolex and I flew together in there doing quite a bit of testing a while back (over a year ago, I believe), and we were able to find some flaws with where the green x told you to shoot under certain circumstances.  We actually had to aim differently in certain situations than the x told us to, in order to score hits.  Honestly, I don't remember the specifics anymore though.  I believe that firing while inverted was one place to see that. 

I do a huge amount of shooting IRL, and pay a lot of attention to how things work.  I shoot flat shooting rifles like my 22-250, and very slow, highly arched smoothbores like my BP Brown Bess (.75 cal).  Even some BP cannons (Although I've now sold mine...)  I pay a lot of attention to detail.  Coming into the game with that knowledge, I'm probably looking for things that most folks don't pay attention to.  Overall, I/we found the "shooting" model to be pretty close, but not quite perfect (I'm not complaining, it's way better than I expected it to prove out, and I have no idea how to make it better...)

A few things to realize when you test-  One, the target is WAY bigger than you think.  It's huge...  The spacing between each ring is ten feet (from what I recall) which makes the center ring 20 feet across, and the total target size is 100ft x 100ft.  What looks like a pretty nice, tight group may actually be 10-15 feet across!  Two, ballistic "facts" like the fact that bullets will strike high when you fire uphill, OR downhill, are modelled correctly.  I believe I see errors when I fire upside down, or in "knife-edge" attitudes, but it's awful hard to test/prove that.  If there are errors there, I can't say that they adversely affect the game.  Level flight is pretty easy, I do all my testing on Auto-level, afetr speed has built up and stabilized.  Remember, in game most people hit things (with guns) less than 5% of the time...  I'm not sure how much more difficult HTC needs to make the shooting...  Also, if you fire while experiencing anything more or less than 1G your results will be skewed.

Another big factor is the vertical spacing between your "line of sight", and the muzzle of the weapon.  The greater that distance the more difficult things get.  When mounting a scope on a rifle, getting the scope as low and close to the barrel as you can is beneficial.  In a plane like the F4U, that vertical distance appears to me to be 5-6 feet.  It's less (so, better...) in a P38 (or any other nose-mount gun).  Draw a line from your eye, through the sight, and to the target.  That's always a straight line...  Now, realize that in addition to tilting the muzzle up to compensate for trajectory, you also need the bullet to "come up" to your line of sight, and generally THROUGH your line of sight (in a hand-held rifle), to drop back down onto the target at range.  My .270 bullet will cross my line of sight at about 25yds, be about 2.5 inches high at 50 yards, and hit the bulls-eye at 100, for example.  If I set my F4U convergence at 100yds, with a flat shooting gun like a .50, where will my bullet hit at 200yds?  Extremely high...  For a 200 yard shot, the .50 has less than 3 inches of vertical "arch".  But in the F4U with it's low guns, in order for the bullet to cross my line of sight at 100yds, its coming up roughly six feet!  That's pretty steep!  With the flat trajectory of the .50's I would guess my bullet would be a little less than 6 feet above the target at 200 yards, roughly 10-11 feet high (above my line of sight) at 300yds, maybe back to only 6-8 feet high at 400, and eventually coming back down to my line of sight...  See what I mean? 

Now, in game, that's not what I see.  I can't get my bullets to hit high (above my line of sight) no matter how close I set my convergence.  Even setting convergence to 200 should result in high hits at 300, when you take the line of sight and flat trajectory into account.  Now, it may have something to do with the sighting system, I don't know...  When we look through the sight, is it basically a pane of glass?  Or are we seeing an image that compensates for the distance between the eye and the muzzle?  No idea...

Now, if we tip the plane on its side, the guns are no longer tilted "up" to compensate for gravity, but to the side instead.  Where should the bullets go now?  Way over to the side due to the tilt of the guns, and way low, because there's no longer any tilt to fight gravity...

Put the plane inverted... now where should the bullets go?  Now the "upward" barrel tilt to compensate for gravity is actually reversed...  The barrels are now tilted to "assist" gravity...  With a convergence set at say, 200yds, the bullets should actually cross through the line of sight earlier, so from the upside down pilots view his bullets will hit high (or completely miss the target, hehe!), which in reality means he's firing well UNDER his target (barrels are tilted down, and gravity is pulling down).

Anyway, there's a lot too it when you really look at it.  And we're only looking at vertical aspects so far.  There's probably more to it than we really want to discuss...

[Cajunn]

I don't think its the flight of the rounds more than its where there all meeting up at. Therefore beings that the cannon rounds or heavier you have to put more lift in them the make them converge at the same point as the lighter MG rounds. By setting the cannon rounds closer then the MG rounds you would in fact be shooting underneath point of convergence of the MG rounds. 

[mtnman]

I don't think its the flight of the rounds more than its where there all meeting up at. Therefore beings that the cannon rounds or heavier you have to put more lift in them the make them converge at the same point as the lighter MG rounds. By setting the cannon rounds closer then the MG rounds you would in fact be shooting underneath point of convergence of the MG rounds. 

If the cannon rounds are set to the same convergence as the MG rounds, they should all pass through the same point at that set convergence distance...  That's what setting convergence is about.

If your MG convergence is set at 200, your bullets should hit the bulls-eye at 200.  If your cannon convergence is set at 200, your cannon rounds should hit the bulls-eye at 200.

Why would you sight in any gun at 200, if you wanted it to hit the bulls-eye at 300?

Convergence sets the desired impact point.  If you need to set the cannon convergence to 300 in order to hit the target at 200, something ain't right...  If setting cannon convergence to 300 results in shots hitting the bull at 200, where do they hit at 300???

Or are we under the impression that HTC has the cannon rounds hitting low at their set convergence?  How low?

[Cajunn]

If the cannon rounds are set to the same convergence as the MG rounds, they should all pass through the same point at that set convergence distance...  That's what setting convergence is about.

If your MG convergence is set at 200, your bullets should hit the bulls-eye at 200.  If your cannon convergence is set at 200, your cannon rounds should hit the bulls-eye at 200.

Why would you sight in any gun at 200, if you wanted it to hit the bulls-eye at 300?

Convergence sets the desired impact point.  If you need to set the cannon convergence to 300 in order to hit the target at 200, something ain't right...  If setting cannon convergence to 300 results in shots hitting the bull at 200, where do they hit at 300???

Or are we under the impression that HTC has the cannon rounds hitting low at their set convergence?  How low?

I noticed the difference in the hanger while setting the convergence on the 109's, pull the MG's out then pull the cannon out until the cannon line matches the MG's line and the cannons about 50 yards further then the MG's. And your point is valid it should match up at the set distance. I don't know if it has to do with the fact that a through the hub cannon is lower then the MG's and you have to aim it higher to match.

[mtnman]

I noticed the difference in the hanger while setting the convergence on the 109's, pull the MG's out then pull the cannon out until the cannon line matches the MG's line and the cannons about 50 yards further then the MG's. And your point is valid it should match up at the set distance. I don't know if it has to do with the fact that a through the hub cannon is lower then the MG's and you have to aim it higher to match.

I just did that Cajunn (first time I've looked at the 109 convergence, hehe!).  I think I see what you mean.  Although, if I zoom in while setting mine, the lines meet when the convergence for both MG and cannons is the same.  If I don't zoom in, it looks like they match when the cannons are stretched further out, but when I zoom in I see the difference.  Those lines are straight, too, so aren't exactly accurate when it comes to trajectory, which is the whole premise behind setting convergence different for MG's and cannons.

It's funny I suppose, but the small difference in trajectory, and the small difference in convergence makes little difference, especially since (from what I can see) the bullets NEVER go above the line of sight.  The small difference imparted by having a different convergence (a few inches at 300 yards?) setting is probably smaller than the modeled dispersion of the guns anyway (which appears far greater in the testing I've done).

And the fact that the cannon is mounted lower than the MG's helps too, since the greater arch in the trajectory will actually bring the cannon rounds up closer to the path the MGs fly.

I mainly wanted to point out that the idea of setting the cannons further out is flawed in reality.  Especially if the cannons are mounted alongside or ABOVE the MG's.

Here's a previously posted digram showing a bunch of convergence info.  I "painted" in some colored lines to highlight what I'm referring to.  The red line is the line of sight.  See how the bullets come up above it?  The yellow line shows a flatter trajectory round, vs the green line which shows the effect of setting a more arching trajectory round further out.  See how the flight path deviates so far from the flightpath of the MG's?  Setting the convergence of both to be the same would minimize that effect.  And in reality, setting the MG's further out than the cannons (reverse of the prescribed recommendation) may give the best "happy medium" of trajectories.

You can also see how firing while banked would cause your rounds to drop low and to the side...



And again, this really matters the most on "stationary" targets, because no matter how you set your convergence, the MG's and cannon won't arrive at the same place at the same time.  That's actually WHY the trajectory is different...  Cannon rounds and MG bullets fall at almost the same speed.  It just takes longer for the cannons to get there, and trajectory is mainly driven by speed and TIME.

[Cajunn]

Love the chart I saved it I hope its ok, and I understand what you are saying and really never zoomed in while setting the convergence I will from now on though. And setting convergence under 200 yards is probably  better because according to the chart it puts your line of fire in your line of sight, because your line of sight doesn't move, right?

[mtnman]

Your line of sight doesn't change.

I don't think I'd set it any closer than 200.  And I don't think I'd set it any further than 400.  But it does come down to your preference.  I set mine at 275. 

The chart shows wing-mounted 50's, nose mounts will vary from what the chart shows.

It's not my chart either, I found it on a different post.

[A8TOOL]

If the cannon rounds are set to the same convergence as the MG rounds, they should all pass through the same point at that set convergence distance...  That's what setting convergence is about.

If your MG convergence is set at 200, your bullets should hit the bulls-eye at 200.  If your cannon convergence is set at 200, your cannon rounds should hit the bulls-eye at 200.

Interesting read  MNTMAN but there is still an argument there. The cannons will drop faster than the 50's which as we know shoot straighter. If your going in a nice straight and level line it would all work out perfectly but if your pulling back on the stick even slightly then everything changes. In the real world I'm sure there is an exact science to this but this is HTC's world. All 50's don't shoot the same here and is dependent on how HTC see's fit to model the planes for use here.

As I said before. HTC has messed with the 51's three times that I know of since AH 1. each time they messed with it they also changed the way it shoots. That can also be said of the F4U-C. When I first started it was the baddest plane of the set. It's now a much different plane compared to that earlier version.

Cannon rounds and MG bullets fall at almost the same speed.  It just takes longer for the cannons to get there, and trajectory is mainly driven by speed and TIME.

Hummm