P-38 Guns

[Tac]

Dont do squat for having 4X .50 cals and 1 20mm in such a close package (guns barely 2 inches apart!).

Takes the same amount of lead to bring down a con with the 4 X.50's of a P-51B outside of convergence than a P-38 at d100.

Many times, almost always in fact, a plane begins a tight turn to avoid a diving 38, I get a clean snapshot at it as it banks, the plane is an x-mas tree from nose to tail as it passes by my nose on its turn.

Now I KNOW that at such close range I AM hitting with all 5 guns. Con flies away with no damage or a fuel leak at the most.

Id understand lag if it was some times, but almost ALL the time? I kill in snapshots with the Yak.. 2 mg's and 1 cannon all the time at d200 or less. So, whats up with the 38's guns? Same range, yet more guns, more firepower and higher ROF. Different results.  

Any shot at close range should be punching a hole the size of the 38's nose, the .50's drilling and the 20mm punching the hole in.

Is there way too much dispersion or what?

[juzz]

Probably dispertion. Imagine the firepower of the Lightning as being like water spraying from an adjustable hose nozzle. In AH it might be set to the "sprinkler" position.  

[Steven]

You may get sprites, but if the cannon round missed hitting the aircraft due to gravity drop or whatever, then it would be very similar to the gunpower of a 51B.  

-Puke
332nd Flying Mongrels

[Tac]

not at d100 or less and your plane is not pulling and its the enemy plane that's flying by your nose during the snapshots. You hit with 5 guns guaranteed. No damage.. guaranteed. Its getting real old real fast.

[Ghosth]

Tac from what I've seen the key to killing with .50's is to get a sustained burst on target in one location. It seems to take a 1 to 2 sec burst or more in a Pony with 6 .50's.

Lighting a con up from nose to tail will put lots of holes in the skin, but there may not be enough hits in any given location to cause major damage.

While I use snapshots a lot myself I really don't expect them to cause any major failure.
An aileron or oil line perhaps, but it's more a softening up thing. Unless you can get hits in the same location 2 or 3 times.

[Toad]

Roger that Ghost. If you can hold them on one spot for a short bit of time... boom. Even buffs.

If you sprinkle 'em around, the plane keeps flying.

[Tac]

So in other words, the concept of concentrated firepower =null in AH?

So much for the convergence issue and the supposed hit power of the P-38. *sigh*

[Urchin]

No, Tac, what I think he means is this (and I may not explain it very well, but I'll try).

When you fire, your bullets are moving in one direction.  They may be moving in more than one plane of motion, depending on your aircrafts motion when you fired, but they are primarily going in one direction.

On a deflection shot, your target is moving in a different direction than your bullets are going.  Say you have a really teeny burst of 4 .50 bullets and 1 20mm round that you fired at someone in a 90 degree deflection shot.  Since your target is moving perpendicular to your bullets, your fire CANNOT be concentrated on one spot on the enemy plane.  Even if the enemy plane runs right into your burst, he will get hit something like this

Plane takes 1 .50 to the tip of the propeller   .

Plane takes 1 .50 to the engine about 3 feet from the tip of the propeller.

Plane takes 1 .50 to an area somewhere in front of the cockpit, about 3 feet from the last hit.

Plane takes 1 .50 behind the cockpit.

Plane takes 1 20mm somewhat lower down and towards the tail of the plane.

I agree that the fire would be concentrated (better anyway) if you were right behind the target and they were not in motion relative to your guns.  In that case you would probably punch an upside down, cyclops-eyed smiley face in their plane wherever you hit.

But when the target plane is in motion relative to your bullets, you just can't get the kind of concentration you need with just the 4x.50s and the 20mm.  If you were in a 190A8 with those hulking 30mm cannons, you'd prolly only need one hit to kill someone- but the P38 doesn't have that sort of firepower.

I probably wasn't all that clear in my explanation, and I'm sorry for that.  I am trying to explain in my own words something that Andy Bush explained to me about "bullet density" on snapshots- I'll edit it and post a link to the thread.

I can't figure out how to post a link to a different thread on the same BB.  Here is what he said to me--


Andy Bush below --
 

Urchin
Here's a quick way to visualize the "density thing"!

Let's say the target is crossing your nose at 90 degrees angle off. You fire early enough to get your bullet stream into the target's flight path.

Now, let's say the target is doing 300KTAS...this is about 500 feet per second. And let's say the target is 30 feet long.

Imagine the projectile path as a cone that is slowly expanding as range increases....at typical convergence ranges, this "cone" may be 10-15 feet wide.

Now, we look at rate of fire and the number of guns in action...we'll go for broke and choose 6 .50 caliber machine guns that fire at about 750 rounds per minute. We'll be generous and say that equals about 80 rounds per second total.

Now we go back to the target. At 500 fps, it crosses the gun line in about .6 seconds...this means less than 8 rounds have a chance of hitting the target under the best of conditions. Not very much unless something serious is hit!

This is the reality of a snapshot...there simply are not very many rounds in the airspace that the target fly through, regardless of how many rounds are fired.

 

I hope this helps explain what I said.  He said above that even if you fired a lot of rounds, the plane would only "fly through" 8 of them or so- and obviously they all would not hit in the same place.  He meant it if the guns were in the wings, but I don't see how it'd be much different with nose-mounted guns (perhaps the hits would be closer together, but they wouldn't hit in the SAME spot).

[ 08-28-2001: Message edited by: Urchin ]

[Tac]

"He meant it if the guns were in the wings, but I don't see how it'd be much different with nose-mounted guns (perhaps the hits would be closer together, but they wouldn't hit in the SAME spot)."

Thats my concern. Wing mounted guns would have most guns either miss or the bullets be hitting the plane too far apart. But when you got 4 .50's and 1 20mm firing in an area no bigger than a soccer ball... that thing should do some serious damage upon impact! Its like getting hit on the chest with the tip of a broomstick compared to getting hit with the broadside of the stick using the same impact forec. Which hurts more? Which does more damage?

On relative moving targets moving THROUGH the stream of fire, the bullets would still hit quite close together,as they were fired quite close together and did not travel at an angle (as do wing mounted guns as they travel towards convergence). The 20mm too! Im talking almost point blank range here, less than d100, its in those cases when the con's topside view almost literally fills your entire view.

Ill need to film some of this so ye can see. I just dont get the lack of punch. I can spray a con at d600 get 2 pings and it may crack open. But I fire at less than d100 and see a LOT of hits all over the plane, and no damage. Dont make sense to me.  

[Urchin]

Do it, if you would.  Film 5 or 6 fights and post a message to me so I can give you my Email address.  

I DO think there are some issue with the hit sprites, I get wierd stuff happening on occasion, like I posted up in the Training Board.  

You are a good stick.  I've flown against you and you fly very well.  I'd like to see exactly what you are describing, but on the film.  Perhaps it will give me a clearer idea of what you mean.

[Widewing]

Originally posted by Urchin:

Plane takes 1 .50 to the tip of the propeller     .

Plane takes 1 .50 to the engine about 3 feet from the tip of the propeller.

Plane takes 1 .50 to an area somewhere in front of the cockpit, about 3 feet from the last hit.

Plane takes 1 .50 behind the cockpit.

Plane takes 1 20mm somewhat lower down and towards the tail of the plane.

I agree that the fire would be concentrated (better anyway) if you were right behind the target and they were not in motion relative to your guns.  In that case you would probably punch an upside down, cyclops-eyed smiley face in their plane wherever you hit.

But when the target plane is in motion relative to your bullets, you just can't get the kind of concentration you need with just the 4x.50s and the 20mm.  If you were in a 190A8 with those hulking 30mm cannons, you'd prolly only need one hit to kill someone- but the P38 doesn't have that sort of firepower.

This is not really an accurate description of the concentration of gunfire, even when the target is moving perpendicular to the shooter. Here's why:

All of the P-38's guns are fired via individual solenoids. All of the Brownings will have virtually identical "lock time". "Lock time" defines the time between the release of the hammer and the firing pin striking the primer. All of the solenoids should have nearly identical field rise times, meaning that all should pull in at the same time, give or take a few milliseconds. So, for all practical purposes, all five weapons will discharge at the same time. Thus, the first five rounds will be heading towards the target in a tight group, equal to the actual gun placement or pattern. When the arrive at the enemy aircraft, they WILL STILL BE IN THE SAME GROUPING (with the exception of the 20mm round, see below). Hence, they will strike the enemy aircraft with the same pattern. There will be no significant dispersion whatsoever, other than ballistic differences between the Brownings and Hispano. As the weapons cycle, all four browings will discharge simultaniously, with the slower cyling Hispano lagging behind. This next series of .50 cal rounds will follow about 80 milliseconds after the first group, and will arrive in a group as well. Obviously, the 20mm round will arrive later. Assuming the enemy aircraft is moving at 300mph across the shooter's path. Then, the aircraft has moved about 35 ft since the first group of rounds struck (this assumes that no attempt was made to pull lead). In all likelihood, this second group will miss altogether. Remember, machineguns fire at a specific rate, and if all are triggered at the same time, this rate can now be identified as groups seperated by the cycle time of the weapons. Think of the Browning's cycle time as a continuous sine wave. with the hispano being represented by a corresponding wave of a slightly different frequency. Therefore, for a long burst you will have two distinct patterns developing with one out of phase to the other. With multiple guns, you simply don't get the "stiching" effect seen with a single weapon or that protrayed by Hollywood. You will get groups of hits seperated by the time/distance equation.

Think of the P-38's weapons as a garden hose.
The concentration will make you very wet. Bring one gun to bear, and all are on target. This provides a downside as well. Miss with one and it's likely that you have missed with all. Wing mounted guns increase the chances of a hit, but nose mounted ordnance tends towards a greater mutiple of hits (except when at the convergence point), therefore more damaging hits should your aim be true.

There should not be any significant dispersion of .50 cal rounds from the P-38, right out to maximum range. Deflection shots will move the 20mm round(s) out of the general pattern due to reduced velocity and slower cyclic rate.

My regards,

Widewing

[ 08-29-2001: Message edited by: Widewing ]

[Urchin]

Ahhh, I see.  Thank you for the information, Widewing  .  

Even so, it would be tough to bring someone down with a snapshot, because now although although 1 "wave" of bullets would probably still hit, you are still only talking about 4 .50 cals and a 20mm shell.  The other "groups" would probably miss because there are big enough gaps between the individual "salvos" (for lack of a better word) of .50 rounds, since they all fire at the same time.  Is this correct or am I still wrong in some way?  I don't know much about the topic, I just tried to infer something from Andy's explanation  .

[Westy MOL]

Fwiw, and I'm no AH ace, but in a turn fight  or other situtations where I have to pull lead for a deflection shot I use only the P-38's .50's. If I have a dead on "6" shot I will I use them all. It usually gives me a pilot kill (well the plane blows up versus suffering other, less amounts of damage) and with the extra 20mm I usually means much less ammo used over all.

-Westy

[HoHun]

Hi Urchin,

here's a quote from Major Robert H. Riemensnider, who flew P-51D with the 55th Fighter Squadron:

"I had previously flown the twin-engined P-38 Lightning where the nose-mounted armament made for an ideal gun platform. Ranging wasn't the problem it was with the P-51 and other fighters which had wing-mounted armament where the fire converged. In our outfit the guns were adjusted for a point of convergence 300yd ahead where, theoretically, they gave an approximately 8 x 10 ft bullet pattern. In practice, because of the speed of closure, it was not easy to  achieve that exact range when you hit the gun trigger. So there was a tendency for pilots to open fire at a target further off and hold a long burst as they closed. If you got in a correctly ranged burst, it was highly destructive. In my opinion the six 0.50in calibre guns of the P-51D were adequate for the job we were doing."

(From Roger Freeman's "P-51 in Combat".)

Due to the variance in cycle times of individual machine guns, I'd disagree with Widewing's "salvo fire" image - it took electrical priming to achieve that kind of accuracy. (Electrical priming in WW2 was only employed in German armament, though.) The P-38 really sent an inhomogenous stream of bullets towards the target. (Cycle time varied with ammunition type as well, and priming introduced an additional random factor.)

That the P-38's Brownings weren't subject to dispersion would appear to be a bit of an exaggeration, but compared to the 8 x 10 ft pattern described by Riemensnider, the P-38's pattern was smaller due to the more rigid mounting of the guns - it was "coffeetable size", as one P-38 pilot said.

In any case, you can safely rely on Andy's explanation - visualize the P-38's fire cone as much smaller than the P-51's, and you get the picture.

(Or think of two intersecting cones extending from the P-51's wings that are only slightly wider than the P-38's single one :-)

Regards,

Henning (HoHun)

[-ammo-]

Originally posted by Widewing:


This is not really an accurate description of the concentration of gunfire, even when the target is moving perpendicular to the shooter. Here's why:

All of the P-38's guns are fired via individual solenoids. All of the Brownings will have virtually identical "lock time". "Lock time" defines the time between the release of the hammer and the firing pin striking the primer. All of the solenoids should have nearly identical field rise times, meaning that all should pull in at the same time, give or take a few milliseconds. So, for all practical purposes, all five weapons will discharge at the same time. Thus, the first five rounds will be heading towards the target in a tight group, equal to the actual gun placement or pattern. When the arrive at the enemy aircraft, they WILL STILL BE IN THE SAME GROUPING (with the exception of the 20mm round, see below). Hence, they will strike the enemy aircraft with the same pattern. There will be no significant dispersion whatsoever, other than ballistic differences between the Brownings and Hispano. As the weapons cycle, all four browings will discharge simultaniously, with the slower cyling Hispano lagging behind. This next series of .50 cal rounds will follow about 80 milliseconds after the first group, and will arrive in a group as well. Obviously, the 20mm round will arrive later. Assuming the enemy aircraft is moving at 300mph across the shooter's path. Then, the aircraft has moved about 35 ft since the first group of rounds struck (this assumes that no attempt was made to pull lead). In all likelihood, this second group will miss altogether. Remember, machineguns fire at a specific rate, and if all are triggered at the same time, this rate can now be identified as groups seperated by the cycle time of the weapons. Think of the Browning's cycle time as a continuous sine wave. with the hispano being represented by a corresponding wave of a slightly different frequency. Therefore, for a long burst you will have two distinct patterns developing with one out of phase to the other. With multiple guns, you simply don't get the "stiching" effect seen with a single weapon or that protrayed by Hollywood. You will get groups of hits seperated by the time/distance equation.

Think of the P-38's weapons as a garden hose.
The concentration will make you very wet. Bring one gun to bear, and all are on target. This provides a downside as well. Miss with one and it's likely that you have missed with all. Wing mounted guns increase the chances of a hit, but nose mounted ordnance tends towards a greater mutiple of hits (except when at the convergence point), therefore more damaging hits should your aim be true.

There should not be any significant dispersion of .50 cal rounds from the P-38, right out to maximum range. Deflection shots will move the 20mm round(s) out of the general pattern due to reduced velocity and slower cyclic rate.

My regards,

Widewing

[ 08-29-2001: Message edited by: Widewing ]

This is not entirely true. Now I dont know about what WW said about the guns firing in a synchronized fashion. Sounds like he knows what he is talking about though so I will assume he is correct. However where I do know there is error is the part where he says that all 5 projectiles from the browning's that fired at the same exact time will remain in a tight group all the way to POI. Each barrel of each individual gun has its own "personality". Every time the gun fires a wave runs through the barrel, this wave is refered to as its harmonics. Harmonics are present in all firearms, but there have been designs that reduce the "wave" or its harmonics, therefore enhancing accuracy. A notable example would be in a target rifle where the barrel has a large diameter, refered to a bull barrel. Other manufacturers mill "flutes"  into exterior surface of the barrel to make it more rigid. What happens when the round is fired is this- The low order burn in the chamber propells the projectile down the barrel. at the same time the barrel harmonics has it vibrating. Where the muzzel of the barrel is in its harmonics when the projectile exits the barrel will have the greatest effect on the POI of the round. Even if you were in a vaccuum, harmanics would cause dispersion at the POI. Now take in effect the enviroment, wind, atmospheric temperature, mass produced ammo ( all ammo is NOT created equal). Handloaders take great care to measure powder charges to help alleviate accuracy problems. Now in WW2, obviously, quantity over quality, was the word for the day. Also another thing, the vibration from all those guns, and the less than rigid mounting, and the consider the AC is not the greatest platform to faciltate inherant accuracy, and you can now see that why there was alot of dispersion, especailly at greater ranges.