Convergence for A6m2....?

[Peyton]

Krusty,
This is great info for other planes too.  Do you have a link or have you published anything that shows what converg. to set on all aircraft.  I know it's personal preference but it would help us New Airmen. It gives us a place to start with the convergence.  Once we practice and get better we can play aroud with the converg.

Thanks

[Krusty]

Whoops, I saw and replied to your PM (which asked the same thing) before I checked this thread. I'll put the same thing on here for public consumption:

There's a lot of info on the forums explaining how the convergence works (including some nice charts to help visualize it), but my main advice to new pilots is this: Find out what distance you actually kill at (not spray 1k out, not lucky hits, actual "I aimed, I shot, I killed" kills) by filming your sorties and reviewing them, then set your convergence to that distance.

Set your convergence to that, and then fire at that distance.

That's going to help any beginner in any plane with any type of guns.

I will say if you end up setting it at 400 or more you're not reviewing the films properly. Chances are most of your "killshots" come under 300 yards.

[mtnman]

Just to be clear, when perfectly level and un-moving, your rounds arc upwards then fall down onto the convergence point (your gunsight crosshair).

This isn't always true...  But I agree with the rest of your post.

Your statement is true for nose-mounted guns, but generally not true for wing-mounted guns.  They all fly with an arched trajectory, but don't all "fall" into the convergence point.

Nose-mounted guns are closer to the line of sight, so the trajectory of the rounds will come up through the line of sight (so, firing closer than convergence causes hits to be high), and then fall back down and cross through the line of sight at the convergence point (assuming level flight at 1G loading...).  Firing beyond convergence range will always result in "low" hits.

Wing-mounted guns though, are mounted well below the line of sight.  This means that the rounds "climb" up to the line of sight, and don't meet it until the point of convergence (so, firing closer than convergence causes hits to be low).  

Depending on ballistics and convergence range, the rounds (from wing-mounted guns) may just meet the point of convergence at the "top" of the arch, and begin to fall (and never cross above the line of sight), or may actually come up through the line of sight at the convergence point and continue upwards for a while before falling.  This would mean that firing beyond convergence-range will result in "high" hits, then they'll be "right on" again, and then eventually "low".  Of course they'll be fanned out all over the place too...  In this example (with a convergence setting of 200yds), the rounds would be "low" all the way to 200 yards, then "high" from 201 yards to some point further out (lets just say 500 yards), where they'll cross/fall through the line of sight and hit "low" from that point on.

Those are just general rules, and will vary quite a bit depending on actual ballistics.  Setting convergence actually gets to be a pretty complicated thing.  It just gets worse when you factor in different mounting points and a wide range of ballistics.

The advice of getting close, and shooting with a fairly close convergence is definitely the way to go though.  Personally, with all the testing I've done in the TA I find it tough to beat a 275yd convergence across the boards, and firing when the counter switches from D400 to D200 (which is actually at 300 yds).  Different opinions are valid too, of course...

[mtnman]

I will say if you end up setting it at 400 or more you're not reviewing the films properly. Chances are most of your "killshots" come under 300 yards.

Man, is that ever true...

[Krusty]

mtnman, they are set to arc up then fall down, it's just the trajectory of the bullets over distance. Wing or otherwise.

AH used to have them reach the "gunsight" at the top of the arc, then they would fall down further out. This was changed at some time (way back, AH2 introduction era if memory serves) so that they reached the top of the arc before the gunsight, then fell back down towards it -- to model real weapons ballistics.

This means a sharper drop-off if a target is further outside your convergence range, as compared to previous AH coding.

[mtnman]

mtnman, they are set to arc up then fall down, it's just the trajectory of the bullets over distance. Wing or otherwise.

AH used to have them reach the "gunsight" at the top of the arc, then they would fall down further out. This was changed at some time (way back, AH2 introduction era if memory serves) so that they reached the top of the arc before the gunsight, then fell back down towards it -- to model real weapons ballistics.

This means a sharper drop-off if a target is further outside your convergence range, as compared to previous AH coding.

I understand that very well Krusty.  I'm much more familiar with "real world" ballistics than AH, but most of the testing I've done has shown me that AH is pretty dang close to RL.

Those "real world" ballistics are why I posted the above.  I could give you charts and stuff to back it up, but if you just sit back and think about it I think you'll see what I mean.

Many (most? all?) of the wing-mounted MG's should in no way cross "above" the line of sight and "fall" back down to it to hit the "bulls-eye" at 200 yards.  Heck, my smooth-bore muzzleloaders have better ballistics than that...

If they did, they would be far from real-world facts.

[Krusty]

smooth bore muzzle loaders probably won't fire 200 yards. Hence why "rifles" in the civil war were the first to be used reliably outside 25 yards.

Not that I'm nitpicking. You probably do know more about the matter than I do, but I do know that 200 yards is a long distance (2 football fields) and to say the 50cal doesn't drop over distance -- IMO that just goes against gravity's laws.


I'll quote a humurous line from way back I've always liked:

"Gravity: It's not just a good idea, it's the law"

[mtnman]

smooth bore muzzle loaders probably won't fire 200 yards. Hence why "rifles" in the civil war were the first to be used reliably outside 25 yards.

Not that I'm nitpicking. You probably do know more about the matter than I do, but I do know that 200 yards is a long distance (2 football fields) and to say the 50cal doesn't drop over distance -- IMO that just goes against gravity's laws.


I'll quote a humurous line from way back I've always liked:

"Gravity: It's not just a good idea, it's the law"

You're quote is pretty good...  The rest we can work on...

Smooth bore muzzleloaders will fire (and are dangerous) much further than 200 yards.  Their ineffectiveness was due to the lack of sights (most used a large bayonet lug instead of a front sight, and had no rear sight at all), and lack of stability imparted to the ball (due to the lack of rifling).  Even without rifling, smooth bores with crude front and rear sights are easily capable of shooting 3 inch groups at 50 yards, and are dangerous well beyond that.

Rifles in the civil war were not the first to be used reliably beyond 25 yards.  Not even close.  Even those cruddy ol’ smooth bores were more effective than that.  Even smooth bore pistols are that effective, if not a bit more.  Rifled pistols are effective beyond 50 yards...  Rifles from one hundred years prior to the Civil War were capable out as far as 400 yards, and possibly as far as 700 yards, depending on the source of the information.

But we stray...  I could go well beyond on this subject, but we can do that in another thread if you want.
_____________________________ ________

200 yards is not a long distance when it comes to ballistics on the guns we're looking at.  Heck, I use my .22-250 for shooting varmints out to 500yds. 

The bullets from a .50 MG drop of course, but to nowhere near the extreme you seem to think.  When it comes to the 50's I'm having trouble finding any bullet drop tables for the ranges we're discussing (they all seem to want to stretch things out to beyond 2000 yards).  However, if we take a rifle I'm familiar with (which likely doesn't shoot quite as "flat" as a .50, the point still becomes clear.

Setting a convergence of 200 yards is effectively the equivalent of "sighting in" a rifle for that range.  The first part of our problem is in visualizing the "correct" amount of arch in the bullets trajectory.  With a .270Win, if I sight it in at 200yds (I generally sight it in a bit further, but 200 will work fine here) the bullet will start below my line of sight (which is a few inches above the barrel; that becomes important later), crosses through my line of sight on an upward slant by about 25 yards, "climbs" to a maximum of about 1.5" above my line of sight at 100yds, and "drops" through the bulls-eye at 200yds.  Carried further, the bullet will be about 6.75" low at 300yds, and 20" low at 400yds.  In total, that's only about 21-22" of "drop" out to 400 yards.  The .50 won't much more than that, if at all.  I expect it actually flies "flatter" than that.

Here's the thing though, about how that applies to AH.  Our eye doesn't sit a few inches above the barrel.  It sits a few feet above it.  The line of sight in question in both cases stays the same though.  It's a line from your eye, through the sight, and out to the target.  In an airplane with wing mounted guns, the barrels are tilted upward much more than a hand-held (or nose mounted) barrel, in order to get the bullet to cross the line of sight at the sighted-in range.  The trajectory of the round stays about the same (although, technically, it'll actually fly "flatter", further, than one fired "level", but with a more pronounced drop in the end; for example, a bullet fired straight up will have no arch at all, until it stops and reverses direction).

Look at these diagrams (sorry, I don't have zero pictures).  In the side view you can see I added lines where the line of sight is in relation to the gun barrels.




An easy way to use these diagrams is to lay a ruler on it, and realize that in this case the propeller is 13'2".  That will allow you to realize that the pilots line of sight is about 4.5 feet above the guns.  Now, if the guns are sighted in "level" for 200 yards, the bullets will never cross the line of sight for the pilot, so will always appear to be "low".  That's because from zero to 200 yards they only "climb" 1.5".  In order to cross the line of sight though, they'd need to come up 4.5 feet (54 inches).  That means the gun barrels need to be angled upward more...

Now, the trajectory doesn't "bend" more to allow for this.  So where does that put the rounds at 400 yards?  How about at 100 yards?  If they shot like lasers, they'd be 2.25 feet low at 100yds, and 4.5 feet high at 400 yards (assuming a 200yd convergence).  Taking real world trajectory into effect, they'd actually be a little less in both places (less low, followed by less high...).  

This ignores that fact that the .50's probably shoot a bit "flatter" than my .270, and that the trajectory will initially "flatten" as the barrels are tipped more towards the vertical.  Take this into account, and the diagram will prove my point even further...

Now, a trip to the TA with the .target will also show this to be true (I've played with it a lot...).  These effects show...  However, they seem to be more subtle than you'd expect, until you realize that the center or "10" ring on the .target is 20 feet across.  That's one heck of a big bulls-eye, and the back of a plane can take up a deceptively small portion of it...

Keep in mind, this applies to wing mounted guns (like the A6M2's 20MM's).  Nose mounted guns are a bit different (and a bit easier).

[Krusty]

mtnman, first I have to call you out on muskets firing up to 700 yards. That's just bull. Max effective range was 50 yards or more, but the range to actually hit what you were aiming at was much shorter. Doesn't matter if it's "lethal" at 150 yards still, if the ball round is 100 feet off to the left and "missed by a mile."

Second, don't get me wrong when I say "they drop" -- they do, but not horribly so. They have a very flat trajectory for sure, but even considering the arc is a shallow one, it's still there. The issue with wing guns is that they're canted upwards (or the gunsight canted downwards?) so that they meet. If the guns were lasers it would be a straight line. They're aimed above the "laser level" and drop back towards the end point in a curve, but because they're lower on the airframe they never rise "above" the gunsights.

They do rise above the line-of-sight [from the barrel to the convergence point], though, and arc back towards the crosshair. When looked at from an angle, they may not rise above the gunsight line, but they do arc up then fall back to the target ever-so-slightly.

Much more noticable with cannons.

[mtnman]

mtnman, first I have to call you out on muskets firing up to 700 yards. That's just bull. Max effective range was 50 yards or more, but the range to actually hit what you were aiming at was much shorter. Doesn't matter if it's "lethal" at 150 yards still, if the ball round is 100 feet off to the left and "missed by a mile."

You seem to be using the term "musket" and "rifle" interchangeably when discussing early firearms, which is incorrect, and may explain your confusion. 

A musket is a smooth bore (non-rifled) firearm, generally of large caliber.  Effective accuracy is at least 75 yards (to hit a man-sized target) for an "decent" shooter.  Since we're also relating this to trajectory, they're "dangerous" beyond that.  I've shot deer out to 100 yards with mine (musket/smooth bore), without difficulty.  That's putting the ball into a 6" diameter target...

A "rifle" has grooves running the length of the barrel designed to impart a rotation to the ball, which stabilizes it in flight.  They're generally of a smaller caliber.  They shoot a smaller projectile at a higher velocity, and have much improved accuracy at longer range (but aren't much more accurate than a smooth bore at ranges of 75 yards and less).

A quick quote on the early rifles-

"The long rifle is said by modern experts to have a range of 80 to 100 yards.[citation needed] This figure is meant for the normal or novice user. A trained, experienced shooter who knows how to take variables into account such as (gunpowder) load, windage, drop, etc. can easily extend the medium range of the long rifle to 400-500 yards.[citation needed] In 1778 at the siege of Boonesborough, Kentucky, one of the officers of the combined British/Shawnee assault force was hiding behind a tree. He stuck his head out from behind the tree and was instantly killed by a ball to the forehead fired by Daniel Boone, who was known for always firing the same fixed measure load of blackpowder in his rifle. This shot was later confirmed by witnesses on both sides and the distance measured at 250 yards. Hitting a target so precisely at that range would probably make the Kentucky Rifle comparable in total effective (long) range with the British Baker rifle at 700 to 800 yards.[citation needed]"

Now, the 500 yard shot sounds nuts, but I've seen it done repeatedly, using a 2' diameter steel plate as a target.  Personally, I can shoot mine (rifle) into a 6" target at 100 yards standing without a rest.  At 200 yards I can hit a paper plate (with a rest), and I seldom even practice at that range...

"Range to actually hit what you're shooting at"??  My flintlock single-shot "dueling pistol" will easily hit a tennis ball, every shot, at 50 yards.  With some effort, a golf ball isn't so tough either...  In competition with our rifles, we shoot the flames off of candles out as far as 50 yards, in the dark, standing, off-hand (no rest). 

I also don't really care for a "Wikipedia" backing, but in this case it ties in pretty close to my own personal experience...  My opinion on these weapons may vary from yours, because I own them and shoot them.

They do rise above the line-of-sight [from the barrel to the convergence point], though, and arc back towards the crosshair. When looked at from an angle, they may not rise above the gunsight line, but they do arc up then fall back to the target ever-so-slightly.

No, they don't.  A quick experiment with the .target will show you that.  Regardless of your convergence setting, your rounds will never rise above the line of sight, at least with wing mounted guns.  And I'm not saying that's correct, because they should rise above the line or sight at some point, just not where you say they will...

Set your convergence to 200yds, and put the .target at 50, then 100, then 150.  Your rounds will hit low on each target.  They'll never hit high.  That part of the trajectory model is correct.

Now, to make that point extremely evident, set your convergence to as close-in as you can get it (let's just say 100yds), and run the experiment again.  You'll see the same effect.  But, at 150 yards they should hit high for sure...  Do they?

[Krusty]

Smoothbore = musket, on the first matter. I thought you were confusing the two with the comment:

Smooth bore muzzleloaders will fire (and are dangerous) much further than 200 yards.  Their ineffectiveness was due to the lack of sights (most used a large bayonet lug instead of a front sight, and had no rear sight at all), and lack of stability imparted to the ball (due to the lack of rifling).  Even without rifling, smooth bores [EDIT: Here's why I thought you were mixing them up, because smooth bores have no rifling, and aren't rifles] with crude front and rear sights are easily capable of shooting 3 inch groups at 50 yards, and are dangerous well beyond that.

Rifles in the civil [...] Rifles from one hundred years prior to the Civil War were capable out as far as 400 yards, and possibly as far as 700 yards, depending on the source of the information.

Since rifling was not found in many individual-carried (i.e. musket/rifle as compared to cannon/artillary) weapons before the civil war, I thought you were confusing them, not me. Sorry.

On the second, I was trying to suggest that "line of sight" was from the barrel to the target. As if you stood with your head where the gun ports were on the wing and looked at the convergence target. Not the gunsight crosshair. The bullets would rise above your line of sight (also the same line I suggested with the "laser" comment) and then fall back down, even if ever-so-slightly. I was trying to differentiate between the former and latter. From the cockpit you wouldn't notice, but from the gun you would.

[mtnman]

Smoothbore = musket, on the first matter. I thought you were confusing the two with the comment:

Since rifling was not found in many individual-carried (i.e. musket/rifle as compared to cannon/artillary) weapons before the civil war, I thought you were confusing them, not me. Sorry.

On the second, I was trying to suggest that "line of sight" was from the barrel to the target. As if you stood with your head where the gun ports were on the wing and looked at the convergence target. Not the gunsight crosshair. The bullets would rise above your line of sight (also the same line I suggested with the "laser" comment) and then fall back down, even if ever-so-slightly. I was trying to differentiate between the former and latter. From the cockpit you wouldn't notice, but from the gun you would.

Ah, ok, some misunderstandings then...  No problem!

The idea of standing with your head next to the wing mounted gun seems odd to me, as that's not how they're sighted in, but anyway...  If you did that, it would effect the line of "sight" idea, for sure.  It would give you a sort of "spectators" view.

I've run some more tests, and will post some charts and screen shots in a different thread to help clear up what is really going on with the vertical convergence thing.  That way it won't be buried in one mainly on the A6M2...

Rifled weapons were carried by many individuals before the civil war though, just not so much by the military.  George Washington himself was initially opposed to rifles in his ranks (and that was pre civil war...).  The rifle wasn't popular in the military initially because the slower rate of fire was seen to be detrimental, and not offset by the much improved accuracy.  Also, rifles are more "picky" when it comes to projectiles, and how those projectiles are loaded.  Early rifles were all "custom", and weren't able to use ammunition interchangeably.  A rifle was sold with a mold to make balls for that individual rifle.  This was pre- industrial revolution...  Imagine how difficult it would be to supply your troops if they all had rifles that shot essentially "custom" ammunition...

The way wars were fought made long range accuracy (rifles) unnecessary, and "undignified".  The thought of using them to snipe officers was appalling...  Officers were supposed to direct their men like chess pieces across the field of battle.  The men were supposed to wear bright clothing, stand shoulder to shoulder, and act like "men".  Firing volleys was seen as the proper way to fight.  A rifleman killing officers at long range was cowardly...

[Nemisis]

I have the cowl gun set to D650, and the cannons set to D375.

[Peyton]

Typical musket calibres ranged from 0.5 inches (13 mm) to 0.8 inches (20 mm). A typical smooth bore musket firing at a single target was only accurate to about 50 yards (46 m) to 70 yards (64 m). Rifled muskets of the mid 19th century were significantly more accurate, with the ability to hit a man sized target at up to 500 yards (460 m).[1] The advantage of this extended range was demonstrated at the Battle of Four Lakes, where Springfield Model 1855 rifled muskets inflicted heavy casualties among the Indian warriors before they could get their smooth bore muskets into range.

[TequilaChaser]

Typical musket calibres ranged from 0.5 inches (13 mm) to 0.8 inches (20 mm). A typical smooth bore musket firing at a single target was only accurate to about 50 yards (46 m) to 70 yards (64 m). Rifled muskets of the mid 19th century were significantly more accurate, with the ability to hit a man sized target at up to 500 yards (460 m).[1] The advantage of this extended range was demonstrated at the Battle of Four Lakes, where Springfield Model 1855 rifled muskets inflicted heavy casualties among the Indian warriors before they could get their smooth bore muskets into range.

it is nice to post your source for others

something like this  http://wapedia.mobi/en/Musket   helps others to possibly make a reply to your post  or respond to your post

hope this helps