Would like some 109 training

[mtnman]

Edit-Never mind this post, I found the result I was looking for with my last test, and it was exagerated by being inverted, as it should be...

I was having trouble finding the "high" shot placement resulting from setting convergence very close.

Just because it helps display the scale of the .target, here's a B17 imposed on it.  Look at all the room in the "10" ring for potential misses!

[moot]

375 is my close guess to what 400 icon range translates to when you account for trigger delay on a closing target (most of my shots).  And it's an old habit from years ago (~2000) when I'd tested MK108 and found that it wasn't worth setting convergence past 350-400 yards because of the MK108's terrible dispersion.

So like I was saying and Mtnman also said with a few differences, it's really something you have to fit to your flying, not the other way around.  Especially when there's only one nose mounted gun that's paired with other guns whose ballistics are different.  Over the years, there's two main categories that MK108 shooters fit in.. One will have the 108 set close and adjust for elevation manually, and the other sets it further out and manually lower their aim on close shots.  Most of the ones I've talked to (never went out and surveyed, this is just from memory) who're in the second group are doing it so that all guns land together at that sweet spot range.  The only significant disadvantage to this is that the MK108 will shoot measurably high (WRT your piper) on a target that's crossing you on your wings' plane while you're flying perpendicularily at the target at high speed.

edit - I've just tested offline on the .target, and there's no appreciable vertical offset at any shooting range from a 375y convergence setting on a 200y target.  So either I've been doing it wrong all these years, or there really is a big difference between a relatively slow target and one that's flying at zero relative velocity.

Such a mindset and lack of sound information lead to a lot of frustration with the gun on my part.

No amount of theory will replace practice.. You can have your piper perfectly on target, and have the 108 rounds fly around it because of dispersion..  Or have a very fast point blank snapshot on a target flying nose to tail across the exact center of your sight, and have the 108 fire just before and just after the target passes by.  It's very frustrating, no doubt.

[mtnman]

No amount of theory will replace practice..

How true!

The theory end of it is important too, though.  Understanding the hows and whys of gunnery, and seeing concrete proof of that theory in practice is very helpful in formulating a logical plan of attack for "in the field" performance.

I spend a fair amount of time on the rifle range testing loads, sight-in distances, effect of wind, effect of sunlight on my sights, effect of different rest materials, etc, and couple that with knowledge from studying ballistic theory and the testing of others.

When it comes time for a shooting competition, or for hunting, my performance is better as a result of the combined practice, study of theory and test results, and an informed decision based on all that, as opposed to a "guess" when things aren't going the way I want them to go.  It eliminates a lot of the "superstition" that can replace factual knowledge.

[moot]

The back and forth between the two is what's vital. You can't load up with theory and expect to convert it into practical results right off the bat .. hehe
I'm trying to think of a way to conclusively determine if the vertical thing on the MK108 is really bogus or not.  I can't believe I imagined it all this time..

[Qrsu]

Looks like I'm going to have a K-4 binge this month. Thanks guys. 

[mtnman]

edit - I've just tested offline on the .target, and there's no appreciable vertical offset at any shooting range from a 375y convergence setting on a 200y target.  

That "should" be a noticable advantage to nose-mounted guns vs wing-mounted guns, as well as the fact that in 175 yards you shouldn't be seeing "huge" trajectory issues, especially at reasonable range.

With a firearm, there are several advantages to getting the barrel as close to the line of sight as possible.  With a centerfire rifle, having the scope mounted "high" and using rings that allow you to shoot using the open sights while looking under the scope isn't considered as desirable from a long-range accuracy view as mounting the scope as low/close to the barrel as possible.

The further from the line of sight, the more steep the bullet must rise to come through the target at the distance the weapon is sighted-in.  The steeper angle exagerates the high/low aspect of shooting at a target that isn't at the sighted-in range.  With a nose-mount, even if the round drops 4 feet in 400yds (which I doubt it does), that would mean that setting convergence at 400 would put the arc about 2 feet high at 200, which will still give a hit on a plane (it won't go so high as to go over the top of it, at any range).  Shooting at longer range gives the intuitive result of a "low" hit.

The same gun, wing-mounted, will be set at a steeper angle to come through the pilots line of sight at 400 yards.  The wing-mounts may be set as much as 5 feet below the pilots line-of-sight.  That means at point-blank range, the bullets may be as much as 5 feet LOW, but at distances FURTHER than 400yds, the rounds will hit HIGH, because due to the exagerated angle, the rounds will still be coming UP through the line of sight!  This is even more pronounced with flat-shooting MG rounds, like the .50's.  Of course, eventually the rounds will fall back through the line-of sight, but that'll be quite a ways out there.  This sets up a counter-intuitive issue where shooting close means shooting too low, and shooting too far may mean shooting too high.  So, if the pilot compensates for a long-range target by aiming extra-high, where do his bullets go?

This is the effect I have trouble seeing in AH, but like I've already mentioned, the gunnery is hard enough as it is...

From an AH view, nose mounted guns put the barrel much closer to the line of sight than wing mounts do.  Nose mounts have the barrel a few inches under the line of sight, while wing-mounts are several feet lower.  Nose-mounted guns should be "more-forgiving" of firing at non-convergence distances.  And we haven't even tossed in the side-crossing effect of wing-mounted guns...

[boomerlu]

The back and forth between the two is what's vital. You can't load up with theory and expect to convert it into practical results right off the bat .. hehe
I'm trying to think of a way to conclusively determine if the vertical thing on the MK108 is really bogus or not.  I can't believe I imagined it all this time..

I agree. Theory gives your practice focus and something which you can measure your progress by. But as with anything where human judgment and motor skills come into play, practice is irreplaceable.

What's helped me the most here are the few pointers about the range transitions and the fact that I know my practice will pay off so I'm encouraged to stick with the gun.

As far as the MK108 "no vertical offset" - that's what I was talking about when I said I didn't really see too much difference. Even at high range convergence settings, there wasn't much difference in bullet drop whether at close or long. It may just be psychological bias. There's a website with comparisons between the 20mms - the convergences seem more important in determining the horizontal crossing pattern than in setting bullet drop.

[moot]

Yes, and that's a big problem for accurate shots with the tank turrets in the game..

I guess if we found the origin and final point of any AH bullet's curve, we could then calculate the exact ballistics of each gun and double-check them against the AH physics' .target at increments of 50 yards..  That'd be more reliable than the error margin from only practical tests inside the game (with joystck wobble, etc.).  Then we could draw trajectory profiles for each convergence setting..

Boomerlu - The vertical thing... I know I saw it many times.. Maybe I'm only remembering vertical shots (where bullet drop from gravity doesn't happen).  But I could swear I've had it happen on level targets too. 

[boomerlu]

I've also seen situations where I have to aim below the target because the bullet is arcing up. That is why I was so confused about the ballistics  . Mostly this becomes an issue only for dead six shots.

Ironic that we find dead six shots more difficult than a deflection crossing shot.

[mtnman]

I've also seen situations where I have to aim below the target because the bullet is arcing up. That is why I was so confused about the ballistics  . Mostly this becomes an issue only for dead six shots.

Ironic that we find dead six shots more difficult than a deflection crossing shot.

Are you sure you needed to aim low for that reason? 

Being somewhat overly picky about my shooting, I've done a LOT of testing with the .target.  I'll set convergence (for say 650, 300, or 150), and then fire at the target with it set at 50yd increments so I can see the 50yd incremental points of impact, and therefore have a decent idea of the trajectory of that bullet, with that round.

I take the "pilot" variable out of the picture by mapping the fire key to my keyboard, and then aiming at the target (fully zoomed in) using the auto-pilot.  I aim at the target, and use slight taps of the rudder trim to move the sight L/R until centered, as well as regulate the throttle so the AoA (which differs depending on speed) moves the sight U/D, so I can center the sight in the target while flying "hands off" and also can fire "hands off".

Doing that, I'm convinced I should see times where it should definately be a requirement to aim low at certain distances, with certain guns, and with certain convergence settings.  In practice, I have a very tough time correlating what I think I "should" find, with what I "do" find.  From the aim-point and down, things seem fine.  What I don't see is much aim-point and up difference.  Certainly not enough to justify or require aiming low.

In-game, I see a scenario that does require aiming low, though, and it isn't due to the trajectory of the rounds.  It's when you're "dead six" on a target, but slightly low (even if only 15 feet or so...).  You now need to aim low to correctly lead your target, since from your low perspective his flight path appears to be slightly down (even if he's flying level).  Aiming low here is actually aiming in front of him, it just appears to be aiming low...  If you attribute this to bullet trajectory, it could be confusing. 

This is like firing on a bird with a shotgun, that has flown directly overhead and is flying directly away.  To hit it, I need to aim under it, which is actually in front of it...  And, in this case as well, it's aiming low for proper lead, not due to the trajectory of the shot.

[boomerlu]

Mtnman - it COULD have been the flight path. For me these are vague memories. Most of my combat shots with the gun (the ones I remember) tend to be glancing snapshots from 30 degrees or so angle off.

Also, that sounds like very good methodology to plot bullet trajectory. You should publish a paper . What you're saying with your experience is: the scientific methodology reveals trajectories where the bullet path does "arc up", but combat experience is saying that you rarely need to compensate for the arc via aim. Is that accurate?

After flying some practice scenarios with the 30mm, I'm becoming more convinced that there's less wrong with the gun than I originally thought. More a psychological thing on my part.

[mtnman]

Maybe I'm only remembering vertical shots (where bullet drop from gravity doesn't happen).  But I could swear I've had it happen on level targets too. 

Other "scary" things should happen here, and maybe they do.  It's very hard to test, since we can't put the .target above us...  These drawings are of the effect of vertical shots with wing-mounted guns, but illustrate the point.  On a pure vertical shot upward, percieved trajectory of the round should REVERSE!  This is a case where aiming low should be a must!  Firing straight down should also require aiming low, for the reason you mention.




Firing inverted?  Another time where trajectory issues get magnified, to the point where with a 300yd convergence, hitting a target 300yds away should be practically impossible by aiming right at it...  Another instance of "reversed" trajectory, and much more exagerated due to gravity.


And what about firing while banked?  This chart shows that pretty well, look at the BOTTOM row of pictures.

[mtnman]

What you're saying with your experience is: the scientific methodology reveals trajectories where the bullet path does "arc up", but combat experience is saying that you rarely need to compensate for the arc via aim. Is that accurate?

Yup, for all practical purposes.  I'd refine that to say you don't need to worry about the arc "above the line of sight (or aim)".  You do, or course, need to think about aiming high for longer shots...

Edit- and I'm not saying thought and effort shouldn't go into the horizontal aspects of setting convergence, especially for wing-mounts.

[boomerlu]

Yup, for all practical purposes.  I'd refine that to say you don't need to worry about the arc "above the line of sight (or aim)".  You do, or course, need to think about aiming high for longer shots...

Right, I could have been more specific, but you caught my drift.

[mtnman]

Another test that may be eye-opening on the trajectory "non-issue" is to do this-

Turn on tracers, go into the TA, and engage auto-level.  Use F3 or F5 (I don't remember which one) and zoom way out.  Move your viewpoint to the side of your plane, and fire the guns.  The tracers may/may not follow the exact path of the rest of the bullets, but should be pretty close...  See how flat they shoot?  Keep in mind, zoomed out, you won't see much drop, because a 5 foot drop may be only 1/32 of an inch or so from the zoomed-out perspective.