P-51b Convergence

[mtnman]

If the convergence is set 650, they do.

Nope, this is the part you have backwards.

I agree with you on the rest; I'm just pointing out that this part is a misconception.

With a convergence of 650, the bullets will not be high at 300-400yd (with wing-mounted guns).  The bullets will be low at 300 yards.

[MK-84]

Disregard, posted in the wrong thread :/  apparently beer has alcohol in it! who knew

[Scotty55OEFVet]

I set all .50 cal equipped AC at 400 because this seems to be where the conv and ballistics cause the most damage to anything you light up

[bustr]

These might help. Never understood why these WW2 diagrams were never in the AHWiki.

From what I've read in 8th AAF documents the assumption for the .50cal was a 1000 yard effective range. Both the P51B/D and P47 were set so the rounds passed up and through the gunsight line of sight at 300-350 vertical convergence dropping back through near 1000. Crossing of the streams horizontal convergence was set to 250-350. I have some NAVY diagrams for the FM2, F6F and F4U-1 but, in the feild the pilots often had their convergence changed to look more like the P51 or P47 diagram. The NAVY command was more concerned with maximum coverage of rounds on Japanese bombers so had very different vert/horz convergences reccomended from their research department. The pilots learned better in the feild what worked to maximise effectiveness.

The FW A8 diagram is for compairison. The long ranges are for bombers and to account for the less than flat trajectory. 250M is the max sweet spot for fighter to fighter getting enough rounds sprayed at a small fast target. The longer trajectory with the MG151/20 is for bombers which are relatively standing still. In the game I set my MG131 and MG151/20 both to 400 which keeps the dispersion and elevation inside of a 30Mil circle between 200-400. Remember in the A8/F8/D9 both the MG and cannon are firing HE rounds. Or so I hope that is modeled into the MG131 in the game.

This is a link to a slide show with everything german WW2 ammo.
http://www.slideboom.com/presentations/292375/German-ammunition,N%C3%A9met-l%C5%91szerek-13mm-50mm

P51B Convergence/Trajectory/Dispersion Chart.




P47 Convergence Chart.




FW190 A-8 Convergence/Trajectory Chart.



Abbreviations/ Translations:

AP = Amour Piercing.
API = Amour Piercing Incendiary.
HE = High Explosive.

Br. = Brand (Incendiary).
Gr. = Granate (grenade).
L/Spur = Leuchtspur (Tracer).
m = mit (With).
O = ohne (Without).
Patr. = Patrone (Cartridge).
Pzgr. = Panzergranate (Amour piercing grenade).
Spr. = Spreng (High explosive).
Sprgr. = Sprenggranate (High explosive grenade).
vk. = Verkürzt (Shortened = It has a short burning tracer).
W. = Warme Übertragung (Heat transmitted = Tracer initiated self-destruction).
Zerl. = Zerleger (Self-destructing element).

[TequilaChaser]

I suggest as mtnman has posted to practice via filming your flights to see at what range you start shooting (  or what range /distance when shooting at an enemy plane you are connecting the most )

then adjust your convergence accordingly.......

but once you figure out which convergence setting is ideal for your preference, then forget about watching the counter and trying to time your firing of your guns with the counter hitting a certain distance!

what you really want to do, is BURN the PLANE SIZE image into your memory........ look at the plane, look at where the wingtips are in accordance to your rings on your boresite, and burn that image into your memory

once you practice this enough, your memory/brain cells will take over and you will not need to worry about the icon counter never again, your memory will tell you "fire now"

this works for all types of shots, dead six, crossing shots, deflection shooting <---- one thing about deflection shooting is to go into the TA or offline and turn on the tracking shot ( Green X ) this will help train your brain to recognize how much lead to allow for deflection shooting depending on the angle, or speed & g's being pulled for a certain angle of attack....... this too can be practiced enough that you can make a mental snapshot ( mental image ) to burn into those brain cells of yours...... then when you find yourself in a particular situation your brain will tell you "Fire Now"

practicing this, and practicing what that mental image/visualization of the plane size looks like  will eventually help your gunnery improve, verses trying to use convergence settings & the icon counter and solely trying to rely on the icon counter to try and fire your guns to shoot down an enemy plane


just a different perspective of how to go about improving one's gunnery in Aces High


hope this helps

TC

[321BAR]

whenever im in my 51s i would have my convergence cross starting at 350yards, the next being 375 and if in the P51D the third (innermost guns) at 400yards

[Peyton]

Nope, this is the part you have backwards.

I agree with you on the rest; I'm just pointing out that this part is a misconception.

With a convergence of 650, the bullets will not be high at 300-400yd (with wing-mounted guns).  The bullets will be low at 300 yards.

SHOOTING FROM A BOMBER QUESTION:
For this question, let's say all things being equal, you are in a bomber tail gun and the enemy is following behind you (closing of course) at the same altitude. I know speed, AoA, wind, etc all play a factor, but to start with let's keep it simple in order to have a place to start from.

So how can I relate all of these examples you guys have given with ballistics, range, etc when gunning from a bomber?
  When do you start to shoot at an icon?  With .50s do you aim high at 1000 or dead center? With .303 do you have to wait until enemy is at 300?
What would be the farthest out you can start shooting with .303 and .50 and what is the optimal range to shoot at?
What distances would you aim high?  What distance would you aim low?
Some planes "lob" their rounds into the bombers so in a bomber what would a good range to start shooting?
In a bomber I use the distance icons more than I do when in a fighter so  what yardage numbers do I look for when shooting?
Do you guys recommend a particular gunsight for the bombers that would help better so you know when to shoot when the plane "fills" a certain part of the gunsight?
Also when shooting from the center bomber from the tail you can see all mg bullets  converge at a certain point..what distance is that?

Thanks

[drgondog]

   

However, this is in fact based on an erroneous assumption on how trajectory works in AH (and in RL).  By setting convergence out that far on the wing-mounted F4U .50's they're actually keeping their rounds LOWER (in relation to the LoS) throughout the range of their bullets.  This works opposite of their intentions.  To get the effect they desire they'd need to set their convergence in very close (@150 yards) but this would also cause them other problems.   
Not for wing-mounted guns (i.e. the P51B).  With a convergence of 650, the bullets are still below the gun sight (and the LoS) at 300 yards (assuming a level shot under "perfect" conditions).  Not all that much too low either (you'd likely hit both wings of a fighter by aiming at the center of its fuselage).
 

If you sight in a 50 or any other caliber to hit point of aim at 400 yards - your actual trajectory will be ABOVE the line of sight all the way out to 400 yards, then below the line of sight beyond 400.

If you are a hunter or target shooter and you want a basic sight in philosphy that says " I want to be able to hold on the heart at any range up to say 250 yards with a 30-06/150 grain bullet - the sight in at ~ 1 3/4" above the bulls eye at 100 yards.  The bullet will be ~  1.5 inches low at muzzle if using a scope (about 3 feet low in a P-51 for a K-14), climb to 1.75 inches above point of aim at 100 yards , reach apogee at about 160 yards at nearly 2" above line of sight, then back to zero Line of sight at 250 and fall off thereafter. 

If you want to zero at 400 yards relative to line of sight the trajectory of the bullet will be way above line of sight for all of the middle range and be dead on at 400, then forever low after that.  If your real life 51 was sighted in at 400 and you were real close you would be shooting under, then in the middle ranges you would be shooting high.

I know my father's 51B and D were sighted for 200 yards... and he believed he never stared shooting until under 300 yards

[bustr]

Was the horizontal convergence at 200 and the reticle adjusted for center on that while the general trajectory was the pass up through at 300-350 and drop back in about 800-1000? Or did his armeror adjust horizontal and vertical convergence to 200 then lock the reticle center to that? The latter would have him shooting high at 300 while the former a bit more straight on relatively. Did he mention what average speed the convergence was adjusted for?

The 51's tail was jacked up on a static stand until the corrisponding nose angle of attack was achived for a given flight speed at a given altitiude. Then the convergence and elevations were set for the guns at which point the armeror set the center of the reticle's piper. Some pilots with more experience had different ideas about their convergence.

The N9 gunsight which was in the P51B and early D models before the K14 had a low and high pipper adjustment that the armeror manualy set and locked from the cockpit. A bit like the 14 degree down 3 degree up visier linie adjustment the Revi16b was capable of to mount in 109's. Then everything else not needing a severe down look to follow a HUB cannon 0 degree line initial trajectory and drop off. From what I can tell by reading manuals the high and low N9 setting corrisponded to near and far shooting requirments like air to air or ground straffing. And then some pilots had different ideas from experience. The most extreme case the Bueamont modification of the MkII in Typhoons from the ring and bar with cellphane tape that lead to the Type I MkIII single dot on the inside of Typhoon and Tempest windscreens.

[drgondog]

Was the horizontal convergence at 200 and the reticle adjusted for center on that while the general trajectory was the pass up through at 300-350 and drop back in about 800-1000? Or did his armeror adjust horizontal and vertical convergence to 200 then lock the reticle center to that? The latter would have him shooting high at 300 while the former a bit more straight on relatively. Did he mention what average speed the convergence was adjusted for?

I had a long talk with several 355th armorers a couple of years ago - more details below. Basically the target (a Hex pattern  for P-51D and square for P-51B) was set at 200 and each of the guns were boresighted individually - one to each individual 'ball' -outboard low, inboard high (IIRC about 2' square patter) for B, same for D except center gun to center target within Hex.  I suspect the armorers had no particularly clear expectation regarding POI at 1000 yards - I know my father would not have.

The reticle was centered for 200 yards to match the center of the target

The 51's tail was jacked up on a static stand until the corrisponding nose angle of attack was achived for a given flight speed at a given altitiude. Then the convergence and elevations were set for the guns at which point the armeror set the center of the reticle's piper. Some pilots with more experience had different ideas about their convergence.

I didn't ask about flight speed but suspect 300 kts - have no idea regarding 'altitude compensation'.  Rough speculation says set for 20K from a ballistic POV and then at sea level your rounds ought to be slightly low for same AoA as there is more drag on the round at SL and the bullet should drop a little more.

The N9 gunsight which was in the P51B and early D models before the K14 had a low and high pipper adjustment that the armeror manualy set and locked from the cockpit. A bit like the 14 degree down 3 degree up visier linie adjustment the Revi16b was capable of to mount in 109's. Then everything else not needing a severe down look to follow a HUB cannon 0 degree line initial trajectory and drop off. From what I can tell by reading manuals the high and low N9 setting corrisponded to near and far shooting requirments like air to air or ground straffing. And then some pilots had different ideas from experience. The most extreme case the Bueamont modification of the MkII in Typhoons from the ring and bar with cellphane tape that lead to the Type I MkIII single dot on the inside of Typhoon and Tempest windscreens.

Good info on the N-9 and of course all the D-5 and -10's had N-9s until ~ Aug/Sept when K-14s were first being installed in the field so the process was the same for B and D until ~ Dec/Jan when nearly all the field mods had been achieved and all the D-15 (and K-5?) and beyond had factory K-14s (IIRC).

The armorers had a 90 degree telescope like device with cross hairs ahich was inserted in the breech of the 50's to actually adjust each gun mount.

As for my fathers B/D I have no idea what the N-9 was set for, nor the base AoA.  He also did not care for any built in dispersion - wanted it on target with max concentration at 175 to 225

Good to chat, you know your stuff'

Regards,

Bill

[TequilaChaser]

If you sight in a 50 or any other caliber to hit point of aim at 400 yards - your actual trajectory will be ABOVE the line of sight all the way out to 400 yards, then below the line of sight beyond 400.

Yes for single gun being fired by a person -  if you are shooting a .50 cal rifle  because your LoS ( your eye ) is right there in line with the barrel of the gun, it most definitely will rise above the line of sight and then drop back down to the target center.......


No for aircraft's wingmounted guns - now in an aircraft with wingmounted guns, the LoS is much higher than the muzzle/barrel of the wing mounted gun, and therefore the bullet will always be below the line of sight until it hits the convergence setting ( or target one is aiming at depending on distance target is away from them )......

Mtnman has posted data acknowledging this many times,  you can do a search for his gunnery / convergence posts / threads

hope this helps

TC

[VansCrew1]

When i was playing back in the day i had mine set to 350. Not only for the 51B but for almost all other .50 cal's. Why? Because it seems to work the best for me, and how my flying style was.

[ink]

I set all my guns to 300.

crossing shots are more for taters...I have found they do not work as well for 50's....you need a bit more time on target with the 50's unless of course you kill the pilot.

so saddling and deflection shooting works better for me with the non cannon, whereas I set up crossing shots for taters 

[mtnman]

If you sight in a 50 or any other caliber to hit point of aim at 400 yards - your actual trajectory will be ABOVE the line of sight all the way out to 400 yards, then below the line of sight beyond 400.

If you want to zero at 400 yards relative to line of sight the trajectory of the bullet will be way above line of sight for all of the middle range and be dead on at 400, then forever low after that.  If your real life 51 was sighted in at 400 and you were real close you would be shooting under, then in the middle ranges you would be shooting high.

Your explanation works with a rifle, but not with an aircraft with wing-mounted guns.  It's a common misconception though, and confuses many people.

The reason your description works for hand-held firearms is because the LoS is only slightly above the barrel.

The reason it doesn't work for wing-mounted guns is because the LoS is NOT slightly above the barrel, but quite a bit higher (roughly 5ft above it for an aircraft like the F4U; I haven't worked out the measurements exactly for the P51).  It's like standing up, and firing your rifle with your toe while it's on the ground.  The bullet will never come above the LoS in that case until it meets the target.  If it does come above the LoS before it hits the target, it would be impossible for it to hit the target.  That's because the LoS has shifted several feet in relation to the barrel.

For a more in-depth explanation look at the thread I linked to earlier.

I know it seems odd at first; I used to shoot competitively and it took me a little while to figure it out myself.

Oops, sorry TC.  Didn't see your post at first.

[mtnman]

Was the horizontal convergence at 200 and the reticle adjusted for center on that while the general trajectory was the pass up through at 300-350 and drop back in about 800-1000?

The range where the rounds "drop back in" wouldn't be "set" on purpose.  It would be an accidental "by product" of what range the convergence point was set at, factored against the height the LoS was above the barrels and the actual trajectory of the bullets.  The bullets will fall back through the LoS on the P51 at roughly the ranges you mention, for 300yd convergence, but that's just because that's how the bullet trajectory is shaped; not because it's "set" to do that.

I'm sure you know that, but it just looks odd the way you posed the question. 

The only way you could "set" the point the bullets come back down through the LoS beyond the convergence point (but based on the convergence point) would be to raise/lower the pilot seat, raise/lower the guns (not tilting them, but physically moving them closer to or further from the LoS), or speed-up/slow-down the bullets themselves to either flatten or increase the trajectory arc. 

That would be a lot of effort especially considering the "convergence" at that extended range would actually be two well-spaced groups triple the spacing of the guns in the wings.  If the guns are spaced @15 feet apart in the wings you'd end up with two large, loose, patterns 45ft apart at 900yds.  Each pattern would be very large (15ft diameter?) due to dispersal as well.

It also looks odd the way you've posed your question in regards to the 200 yard "cross" compared to the 300-350 pass through the LoS. 

Have you found that they may have set the guns to converge at a point other than the LoS/gunsight at the range the bullets cross through the sight?  So the horizontal component would be set fro 200 yards while the vertical was set for 3-350?  That seems phenomenally odd, but I suppose that doesn't mean it didn't happen.