Why so few planes that fired thorugh the propeller hub?

[fastmongrel]

Hartman could have been armed with a single Lewis Gun and he could still have shot a lot of planes down. Unfortunately he was one in tens of thousands the average pilot from all airforces struggled to hit a barn door at 100 yards. Did the RAF ever investigate wing root mounted synchronised cannons such as some models of 190 carried, that would seem a compromise for a Merlin powered plane.

 

[Shortround6]

I am not sure how far the investigation would have gone, you can't synchronize a Hispano gun. This means you need a whole new gun.

You also cannot synchronize the entire pre-war and war time Oerlikon line of guns. Germans had to go to electric primers to synchronize the Mg 151.

So far I have not seen any real study of the one in the fuselage=two in the wings question, that was done in an armament research establishment. We have a lot of opinions by pilots, some of whom were very experienced. But few of these opinions have any real depth to them. Depth as to which guns they were talking about,which targets they were considering, what ranges they firing at, etc.

Some of the British firing patterns were less than ideal. They were trying to compensate for lack of ability of their pilots (in part due to poor gunnery training) with a 'shotgun' pattern (aiming guns in different directions and never getting a concentration of guns at any range). Blaming that effect on wing mounting of the guns isn't following a true cause and effect path.

A P-47 had it's outer guns about 20ft apart. some smaller fighters had their guns (or at least their cannon) only 12-13 feet apart. Shooting at a skinny fighter plane this may make a difference, shooting at a bomber with fuselage over 6ft wide and an 70-100 ft wide wing?

I can certainly believe that one hub mounted MG 151 was worth two wing mounted MG/FFM cannon but we are not comparing the same thing anymore. Is one hub mounted MG 151 worth two under wing mounted MG 151s?

was there a problem with the gondola mounted guns? like did they have a bigger dispersion pattern due to flex in the wing or mounting? Maybe they didn't, just pointing out a possibility.

the Hub gun is mounted close the the center of of the aircraft vertically, firing the gun will have little (if any) effect on the attitude of the plane (pitch up or down). Wing mounted guns may cause a pitch down when fired. Not so much on things like an F4F with it's mid mounted wing or the P-47 and F6F but on planes with wings at the very bottom of the plane? Guns mounted under the wing have even more leverage to cause pitch down. But this is going to vary from plane to plane.

Some modern fighters with off center guns have the computer controlled rudder automatically feed in deflection when the gun is fired.

Those pilots believed what they said, but detailed explanations seem to be lacking.

 

[Shortround6]

At which range (normal circumstances) were wing mounted guns adjust, that the shells meet in the centerline?

Could Hartmann has fought his style, to close to 100m and below at the enemy, with wing mounted guns?

In part, it depends on the target. Shooting at Yaks, Laggs and even IL-2s the wing mounted guns might have missed more. Shooting at even DB-3/IL-4s???

diagram for a P-47:

This is about as bad as it gets for for a single engine fighter. Please note that with a 250 yd convergence the mean impact points are about 12ft apart at 100 yds. from 200 to 300 yds the mean impact points are never more than 4 ft apart.

 

[stona]

Good stuff. That 4' of divergence isn't going to miss much. The fallacy in the centreline argument is that that same 4' divergence makes the wing mounted armament more likely to score hits for the vast majority of pilots.
I do think some of the RAF's patterns were erring too far in favour of the bad shot, and in so doing penalising the few who could actually hit something. It's the result of the data they had collected showing just how bad most of their pilots were at air to air gunnery.
Cheers
Steve

 

[swampyankee]

USA didn't believe in cannon, hub or otherwise. Not much point in having a hub mounted M2 .50cal MG.

The P-38, P-39 and FM-1 were spec'd with cannon armament well before ww2: the P-38 and P-39 in 1937 and the FM-1 somewhat earlier.

 

[Ivan1GFP]

A good shot will be a good shot wherever his weapons are situated. The convergence of wing mounted weapons was adjusted to some extent to compensate for the inability of most to shoot accurately and again a centre line weapon won't help that.
It is interesting that in the example I gave above for the 150 Wing Tempests against the V-1s that their cannons were point harmonised, something that Squadron Leader Beamont had to argue forcefully for with 11Group. He got his way and it obviously worked.

The layout of the armament cannot make a bad shot better, nor will it prevent a good shot being successful. A good computing gun sight will make the average pilot a better shot, whatever weapons he is using.
It was the opinion of some pilots that a centre line weapon might have been better than their wing mounted armament but they had no way of knowing if this was actually so. The grass is always greener etc.....

I will have to disagree with you on this because I don't believe your assumption makes sense.

Yes, a good Marksman is a good Marksman regardless of the weaponry. The weaponry, however, DOES determine how critical and useful marksmanship can be. For small arms, a man with a shotgun cannot be effective beyond 50-100 yards no matter how good he is. A good accurate rifle will reward tbe better marksman.

For aircraft armament, if we have a few wing machine guns mounted as on a Spitfire all harmonised to 250 yards or so, regardless of the skill of the pilot, the armament cannot produce a useful concentration of fire out at say 750 yards. If the guns have similar ballistics such as the centerline armament of a Me109F/G, then a good marksman can still make hits out at a distance if he can calculate the proper elevation.

Regardless of actual experience with centerline armament, a good marksman will figure out that the configuration on something like a Spitfire is not effective at a distance.

The case of Tempest versus V-1 is a very special case. There is no need to make deflection shots and the target is non-evading so there is the opportunity to set up for a known distance shot to optimise the effectiveness of your armament.

Regardless of skill, there are certain armament configurations which are entirely unsuited for certain things. A while back I remember seeing an argument about why the mixed armament of the A6M was unsuited to deflection shooting because of the different trajectories of cannon versus MG.

Regards.
- Ivan.

 

[stona]

I will have to disagree with you on this because I don't believe your assumption makes sense.

Yes, a good Marksman is a good Marksman regardless of the weaponry. The weaponry, however, DOES determine how critical and useful marksmanship can be. For small arms, a man with a shotgun cannot be effective beyond 50-100 yards no matter how good he is. A good accurate rifle will reward tbe better marksman.

For aircraft armament, if we have a few wing machine guns mounted as on a Spitfire all harmonised to 250 yards or so, regardless of the skill of the pilot, the armament cannot produce a useful concentration of fire out at say 750 yards. If the guns have similar ballistics such as the centerline armament of a Me109F/G, then a good marksman can still make hits out at a distance if he can calculate the proper elevation.

Regardless of actual experience with centerline armament, a good marksman will figure out that the configuration on something like a Spitfire is not effective at a distance.

The case of Tempest versus V-1 is a very special case. There is no need to make deflection shots and the target is non-evading so there is the opportunity to set up for a known distance shot to optimise the effectiveness of your armament.

Regardless of skill, there are certain armament configurations which are entirely unsuited for certain things. A while back I remember seeing an argument about why the mixed armament of the A6M was unsuited to deflection shooting because of the different trajectories of cannon versus MG.

Regards.
- Ivan.

The chances of anyone hitting anything at 750 yards, even with late war gun sights is almost zero, a very lucky shot. SR6 already posted evidence for the P-47, on which the guns are about as far apart as any aircraft and considerably further than most RAF types, that from 200-300 yards, the range at which a good shot would reasonably expect to score some hits, the divergence was never more than 4' .
If a pilot aims 2 or 3 feet off with these weapons he will still score hits from 250-300 yards. A centreline weapon under the same circumstances will miss.
The average pilot is more likely to score hits with some kind of pre-determined convergence pattern. Which pattern works best was and still is an on going argument. It's why it was done. I don't see how a single centre line weapon can bestow any advantage except for the VERY rare good air to air gunners or an occasional and statistically insignificant lucky long range shot.
Someone has already pointed out that all the statistics support that the vast majority of pilots couldn't hit a cow's ar*e with a banjo.
The Newchurch Wing Tempests were a special case, it's why they alone adopted a single point synchronisation. They hit 500 V-1s in a month and I absolutely guarantee they were not all hit from the exact range at which that point was set. I don't have figures for the Tempest but given that the guns are closer together than on the P-47 it is reasonable to estimate that they would have at least a 100 yard window in which they might hit a target as small as a V-1. It didn't take many 20mm cannon shells to put one down.

Given your comment about the Zero what makes the armament of the Bf 109 suitable for deflection shooting?

Cheers
Steve

 

[Shortround6]

Trying to fire at 750 yds air to air depends on sheer luck. 400-500meters is pushing it even against bombers. Luftwaffe figured the effective range of most of their guns as 400 meters against bombers. And BTW the guns on a 109F/G did NOT have similar ballistics. The muzzle velocities may have been close but shape of the projectiles and sectional density means their times of flight and trajectory at long range (400 meters and more) started to diverge rather sharply.

Lets just look at gravity. At the end of 1 second our bullet/projectile will have dropped 16 ft and is falling at 32feet per second. The drop is gotten around by aiming the gun up somewhat. BUT at the end of the 2nd second of flight the total drop is 48 ft and the bullet is falling at 64 feet per second and increasing. 1/10 of second is worth over 6 feet of drop.

Time of flight to 600 meters for some German guns was 1.1 to 1.6 seconds ( with a few guns like the 15mm MG 151 being a big exception) but velocities had dropped 41-60% at that distance. This is measured at sea level and time to distance at higher altitudes is a bit shorter. But then our hero pilot has to try to figure the difference depending on the altitude he is flying at???

At 300 meters only the worst guns (MG/FF and MK 108) had times of flight over 0.5 seconds.

You can deflection shoot with mismatched weapons, you just have to do it at short range.

 

[Juha]

I will have to disagree with you on this because I don't believe your assumption makes sense.

Yes, a good Marksman is a good Marksman regardless of the weaponry. The weaponry, however, DOES determine how critical and useful marksmanship can be. For small arms, a man with a shotgun cannot be effective beyond 50-100 yards no matter how good he is. A good accurate rifle will reward tbe better marksman.

For aircraft armament, if we have a few wing machine guns mounted as on a Spitfire all harmonised to 250 yards or so, regardless of the skill of the pilot, the armament cannot produce a useful concentration of fire out at say 750 yards. If the guns have similar ballistics such as the centerline armament of a Me109F/G, then a good marksman can still make hits out at a distance if he can calculate the proper elevation.

Regardless of actual experience with centerline armament, a good marksman will figure out that the configuration on something like a Spitfire is not effective at a distance.

The case of Tempest versus V-1 is a very special case. There is no need to make deflection shots and the target is non-evading so there is the opportunity to set up for a known distance shot to optimise the effectiveness of your armament.

Regardless of skill, there are certain armament configurations which are entirely unsuited for certain things. A while back I remember seeing an argument about why the mixed armament of the A6M was unsuited to deflection shooting because of the different trajectories of cannon versus MG.

Regards.
- Ivan.

Hello Ivan
life is too complicated to that kind certainties.

The last but one Neville Duke's kill (Bf 109G-8/R5, Duke flying Spit VIII) DUke opened fire, according to him from 600-800y, according to his wingman from 800y and got immediately cannon hits in.
Another one, 2Lt Olli Puhakka, flying not his regular plane but the only FiAF Fokker D. XXI armed with 2 20mm Oerlikon wing cannon, FR-76, tried to catch a fleeing Soviet DB-3 bomber from 53 DBAP, he got 500-700m behind it but when he noticed that distance rather increased than decreased opened fire firing 3 short bursts, first went under the target but other two hit. That in spite of the fact that one of the cannon didn't fire. The DB craslanded and the crew was captured.

Juha

 

[Ivan1GFP]

This is a cool little bee's nest, but we are all friends, right? So here goes:

I personally have no experience in air to air gunnery except in flight simulators, but I do have a reasonable amount of experience with small arms at short to medium ranges, so I will be using a few analogies from that area. I have never fired any metallic cartridge guns that were any more powerful than a .50 Browning. I have no experience with cannons of any kind but do recognise that the ballistic coefficients are much higher as the caliber goes up.

First of all, this discussion was about the superior / expert marksman. I don't disagree that the average fellow could not hit anything past about 300 yards or so. The same is true with small arms. The distances are also remarkably similar against man sized targets, but that is not the target here. The target here is somewhere between the size of a dump truck and a semi-trailer with bombers being even larger. Aeroplanes are not small.

Machine guns are also terribly inaccurate. A good rifle should be able to put 5-10 rounds into 1 inch at 100 yards (1 Minute of Angle). A typical bipod mounted Light Machine Gun (Browning Automatic Rifle) might hold a 1 foot group at 100 yards if fired single shot. A typical tripod mounted Light / Medium MG might do well to put its rounds into a 3 foot circle. I expect an aircraft MG to be even worse than that because of the abuse that they take. The point here is that a 3 inch or 6 inch or even 1 foot difference in trajectory is pretty much meaningless. A one foot difference at 100 yards is still only 10 feet at 1000 yards and your targets are bigger than that.

Gravity does have the 32.16 feet / 9.8 Meters per second effect, but the drop numbers quoted in a prior message are working on the assumption that the projectiles are launched at zero elevation. Guns are typically mounted with some elevation to zero them at a particular range..... Well MOST guns. Consider that the motor cannon on a Me 109 is sitting behind several feet of blast tube, so I don't imagine you could crank in much elevation. (I don't know what the inclination of the thrust line is in the 109 and believe that the aircraft flew a touch nose down.) The cowl guns, however, would have no issues with elevation.

Point blank range is a term that is used a lot but seldom correctly. It is the distance at which a shot can be properly aimed at a target without any elevation adjustments. A flat trajectory (better ballistic coefficient round) increases the distance. A larger target ALSO increases the distance. (A tank gun PBR is typically around 2 kilometers.)

When the US Army used the M1903 Springfield RIFLE, its Maximum PBR was calculated at 550 yards. This meant that a shot aimed at a man's belt line would go no higher than the top of his head or lower than his feet out to 550 yards. This is on a 6 foot man. Aeroplanes are a LOT bigger which would increase the PBR.
Ballistically, the .30 Cal M1 (172 grain FMJBT 2600 fps) is pretty comparable to the 7.92 mm Heavy Ball round (196 grain FMJBT 2500-2600 fps).

The MG 151/20 has a muzzle velocity of between 2300 and 2625 fps depending on ammunition. Bigger rounds are ballistically more efficient but these projectiles are also a lot less aerodynamic. The other cowl gun was the MG 131 which had a fairly low MV of only 2450 fps.

The MK 108 MV is only 1650 fps so it should fly a LOT worse than the rest even though the projectile is even larger.

I haven't run these numbers through a ballistics program to do a more exact comparison though. I believe that the differences in flight path would be entirely hidden in the typical dispersion of an automatic weapon.

With the A6M series, the Type 99-1 cannon had a MV of only around 1722 fps so that would also make it a lot worse than the other guns being discussed except for the MK 108.

Thoughts?
- Ivan.

 

[DonL]

The last but one Neville Duke's kill (Bf 109G-8/R5, Duke flying Spit VIII) DUke opened fire, according to him from 600-800y, according to his wingman from 800y and got immediately cannon hits in.

That's one of the most suspicious post I ever read! You will tell me he hit immediately at 800 Yards? Is this some story for your Grand Grandmother?
And you are a person who questions in a strong way the kills of Hartmann and will tell somebody opens fire at 800 yards and hit immediately?

Are you realy believing this ****?

I'm out!

 

[wuzak]

Machine guns are also terribly inaccurate. A good rifle should be able to put 5-10 rounds into 1 inch at 100 yards (1 Minute of Angle). A typical bipod mounted Light Machine Gun (Browning Automatic Rifle) might hold a 1 foot group at 100 yards if fired single shot. A typical tripod mounted Light / Medium MG might do well to put its rounds into a 3 foot circle. I expect an aircraft MG to be even worse than that because of the abuse that they take. The point here is that a 3 inch or 6 inch or even 1 foot difference in trajectory is pretty much meaningless. A one foot difference at 100 yards is still only 10 feet at 1000 yards and your targets are bigger than that.

And yet the M2 Browning, which was used as an aircraft gun in WW2, would later be used as a sniper rifle.

M2 Browning - Wikipedia, the free encyclopedia

I understand that a machine gun firing in automatic or semi automatic mode when mounted on a tripod or bipod would not be able to maintain accuracy. But why would they be inaccurate in single shot mode? Is it simply because machine guns are made less precisely?

 

[Shortround6]

I believe your estimates for the accuracy of the bipod mounted mg and tripod mounted mg are way off. While not lazer beams and not as good as a rifle (and BTW WW II service rifles were only good for about 3-4 minutes of angle, 6-8 in groups with service ammunition at 200 yds) a "tuned" water cooled Browning could make a 10 shot group, all bullets touching on the 1000 inch (27.7 yds) range. In fact it had better be able to shoot that good if the Unit machine gunners were to earn their "expert" Badges. Tripod mounted MGs were intended for long range fire, granted it was area fire and not point fire but a gun that fired a 3 ft group at 100 yds would be rather unpredictable at 2000yds. These guns were used for "overhead fire" or shooing over the heads of troops hundreds of yards in front of the guns, guns/ammo that "dropped" ocasional rounds 10-15ft below the intended flight path at 1000 yds would NOT have been looked on with favor. Group sizes tend to grow as sort of a bell or curve, not straight lines. Aircraft should be no worse unless the mounts were designed for dispersion as a deliberate policy, or there is a weakness in the mount/supporting structure.

I mentioned the drop as a comparison between guns/ammo. I did say that you could point the guns up a bit ( and it only takes 1/3 of a degree or less to zero for 600yds. It is after these ranges that things can very weird, very quick. a weapon that has 0.2-0.3 seconds longer time of flight to 600 yds than another gun mounted on the same plane can be zeroed for the same impact at 600 yds/meters BUT it will not match at other ranges, and on a moving target it requires a different lead.

My long range .308 using a pretty streamline bullet and a MV of 2950fps ( do not use this load in a semi auto) drops 5 feet between 900 and 1000 yds. and one mph of cross wind is worth "about" 1 minute of angle on the sights (14 mph cross wind needs 14 minutes or 140 inch correction) If I remember right. And 'windage' is another example of long range gunner problems, doubling the range usually increases the wind drift about 3 1/2 times for the same value wind, due to the longer flight times.

A few inches here or there is not of much concern. and at close ranges are nothing to worry about. At long ranges (500-600yds/meters and more) ALL the errors keep piling up making successful long range aircraft fire increasingly iffy. Other pilots may do better but some British pilots in "tests" misjudged the range by up to a factor of 3. That is opening fire at 3 times the range they had been instructed to do so.

 

[Shortround6]

And yet the M2 Browning, which was used as an aircraft gun in WW2, would later be used as a sniper rifle.

M2 Browning - Wikipedia, the free encyclopedia

I understand that a machine gun firing in automatic or semi automatic mode when mounted on a tripod or bipod would not be able to maintain accuracy. But why would they be inaccurate in single shot mode? Is it simply because machine guns are made less precisely?

The gun normal fires open bolt. When the trigger is pressed the bolt is released and flies forward, feeding a round into the chamber and then releasing the firing pin after the bolt locks up. This is a fair amount of time and a lot of moving weight and banging around before the gun goes off. The gun (M2 Browning)can be adjusted or "tricked" into the bolt closing on a live round without releasing the firing pin. The Firing pin is released separately for single shot fire. some other guns cannot do this.
Also note that Sgt. Hathcock used a tripod with elevation and windage controls like this one.

They were sure not trying to use pintel mounts.

A hand wheel on a threaded rod to control elevation and a lock on the traverse bar under the elevation rod to fix the gun in position. A generous allowance of sandbags would also be used to help hold the gun/tripod in position. One of the pre war tricks on the .30 cal water cooled was to use a tent stake behind the rear tripod leg to prevent vertical stringing. Or

Note tripod leg ends fitting into cleats on the T shaped firing platform.

what the "gun" could do and what the gun/mount combination could do are not the same thing.

Please remember that a 300mph airplane is covering 440 feet per second or 44 ft in 1/10 of second. Even if you are behind an aircraft at exactly 6 o'clock and at a distance that takes 1 second time of flight ( and yes your shells do get a boost in velocity) the target aircraft will move forward 440 ft. before the shells get there. Will that cause you to shoot low? Tracers will tell you where you should have been aiming one second ago.

This is the big difference between air to air shooting and ground shooting. Say you are at 6 O'clock but not perfect. target aircraft is actually flying at 3 degrees to your course, can you see it? as it moves 440ft (147 yds) it will wind up 14-15 ft to side of where you aimed.

I can believe somebody opened fire at 800yds and hit right away, the question ( actually the 2nd question) is could he do it again the next day

1st question is how did they KNOW it was 800yds, what were they using for a range finder?

People have gone to Las Vegas or Monte Carlo and rolled sevens 7 times in a row playing craps. It is the stuff of legends, but all the rest of the gamblers who try are what keep the casinos making big money

 

[Aozora]

I came across some RAAF instructions on harmonising the P-40E's guns

View attachment RAAF P-40 Harmonisation.pdf

The RAAF stipulated that the .50s be harmonised at 300 yards.

 

[Aozora]

That's one of the most suspicious post I ever read! You will tell me he hit immediately at 800 Yards? Is this some story for your Grand Grandmother?
And you are a person who questions in a strong way the kills of Hartmann and will tell somebody opens fire at 800 yards and hit immediately?

Are you realy believing this ****?

I'm out!

There's no reason not to believe that Duke got in a lucky shot, because such things do happen. The actual report reads:

I engaged the port E/A from astern at 10,000 ft, fired a short burst at very long range (6-800 yards) in an attempt to slow it down, and observed a bright flash in the fuselage from cannon strikes. I rapidly closed and fired another burst, observing the hood fly off and what appeared to be the pilot leaving the a/c. E/A was seen going down and catch fire by F/O Hamer, my No.2, in area M.5820.
I then continued after the other two E/A still going NW at approximately 10,000 ft. E/A started diving and then went into a steep climb up to about 14-15,000 ft. I quickly caught E/A in the climb as my supercharger came in and closed with the leader as he levelled off. After firing a burst at fairly long range (3-400 yards) and observing no strikes I closed to about 200 yards and scored strikes behind the cockpit, presumably in the rear petrol tank, as E/A started to burn in the fuselage.

Lt Raynor Field: S/Ldr Neville Duke

Duke was probably as surprised as anyone that he hit the 109 because all he was trying to do was force the pilot to slow down - the next 109 he went after he missed at 3-400 yards.

 

[Ivan1GFP]

I believe your estimates for the accuracy of the bipod mounted mg and tripod mounted mg are way off. While not lazer beams and not as good as a rifle (and BTW WW II service rifles were only good for about 3-4 minutes of angle, 6-8 in groups with service ammunition at 200 yds) a "tuned" water cooled Browning could make a 10 shot group, all bullets touching on the 1000 inch (27.7 yds) range. In fact it had better be able to shoot that good if the Unit machine gunners were to earn their "expert" Badges.

First of all, the numbers I quoted for machine guns were not estimates. They are from what I recall from gun tests in various publications over the years. Perhaps my memory is faulty but I don't believe so.
From having fired many 20th century military rifles, 2.5-4 MOA sounds like typical accuracy from a rack grade M1 Garand firing service ammunition (we were shooting LC 67 and LC 68 ). A typical bolt-action does a bit better at around 2 MOA to 3 MOA with oddballs like the Swedish Mausers doing a LOT better. Some examples do better, some do worse, but this is typical of what I have encountered.

Ammunition for MGs for overhead fire during training comes from select lots which are much better quality than typical service ammunition (at least for the US military). I don't know if this is the same stuff used for qualifications.

Think about what you just claimed for your water cooled Browning: perhaps a 1 inch 10 shot group at 27 yards? Would that be around 4 MOA? I am curious as to how these guns were tuned. Perhaps all shots touching is a bigger group than that?
Also keep in mind that recoil operated guns are notoriously inaccurate which is why other than the Johnson rifle, pretty much no one uses this type of action in a semi-auto rifle. For MGs and pistols, it doesn't matter.

I mentioned the drop as a comparison between guns/ammo. I did say that you could point the guns up a bit ( and it only takes 1/3 of a degree or less to zero for 600yds. It is after these ranges that things can very weird, very quick. a weapon that has 0.2-0.3 seconds longer time of flight to 600 yds than another gun mounted on the same plane can be zeroed for the same impact at 600 yds/meters BUT it will not match at other ranges, and on a moving target it requires a different lead.

Agree with you on elevation: 42-44 MOA (0.75 degrees) from a 100 yard Zero to get to a 1000 yard Zero with a typical 168-175 grain boat tail spitzer at 2600-2650 fps. I have never fired AP rounds at targets, but a .30 cal AP bullet has about the same weight and MV though it isn't a Boat Tail.
Disagree with you on what the result is. Keep in mind we are discussing what an expert air to air marksman can do. Making a high deflection snap shot in a twisting dogfight changes everything.

My long range .308 using a pretty streamline bullet and a MV of 2950fps ( do not use this load in a semi auto) drops 5 feet between 900 and 1000 yds. and one mph of cross wind is worth "about" 1 minute of angle on the sights (14 mph cross wind needs 14 minutes or 140 inch correction) If I remember right. And 'windage' is another example of long range gunner problems, doubling the range usually increases the wind drift about 3 1/2 times for the same value wind, due to the longer flight times.
.

Sounds like you have a Palma rifle. They aren't really representative of service guns. Keep in mind that because the .308 cartridge is mandated for competition, folks are playing all kinds of tricks to juice up the MV to keep a HPBT Match bullet above the trans sonic range out to 1000 yards. Your objective is target accuracy. We are discussing aeroplane hitting accuracy and the reason I picked 750 yards is because I believe rifle caliber bullets aren't that different from a medium velocity cannon out that far. My typical .308 load of 168 grain HPBT at 2640 fps is closer to what a rifle caliber AP round would be doing in my opinion. I push these same bullets out to a bit past 3000 fps in other guns, but that also isn't terribly relevant to a rifle caliber MG.

Your 14 MOA correction is interesting but a bit simplistic. The correction isn't a constant MOA. The MOA increases as range increases. In any case, the REAL question is how different a rifle caliber round flies as compared to a 20 mm cannon round, and I do not believe there is a great difference.

A few inches here or there is not of much concern. and at close ranges are nothing to worry about. At long ranges (500-600yds/meters and more) ALL the errors keep piling up making successful long range aircraft fire increasingly iffy. Other pilots may do better but some British pilots in "tests" misjudged the range by up to a factor of 3. That is opening fire at 3 times the range they had been instructed to do so.

I contend that a few inches is not all that important when your target is the size of an aircraft and your dispersion is typical of a machine gun. I figure even 10 feet isn't all that important. Regarding your "some British pilots", these guys were obviously NOT the expert marksmen we were discussing.

I believe the discussion was about whether there was an advantage for centerline armament for an expert marksman which presumes he knows how to judge distance and proper lead.

Regards.
- Ivan.

 

[Rufus123]

I know this strays off topic a bit.

I don't know what the typical MOA is of most military rifles is but a 1903 Springfield I once had was much better than the numbers talked about. I got a large number of sub moa groups out of it but was using a Leupold 1.75 x 6. I also got quite a few 1.5 moa groups most of them were closer to 1 moa.

Maybe this was a better than ordinary example and I don't know how much it being a sporter had to do with it.

 

[Juha]

That's one of the most suspicious post I ever read! You will tell me he hit immediately at 800 Yards? Is this some story for your Grand Grandmother?
And you are a person who questions in a strong way the kills of Hartmann and will tell somebody opens fire at 800 yards and hit immediately?

Are you realy believing this ****?

I'm out!

Combat reports of Duke and his wingman in verbatism on Dike's War Diaries, but why I believe it, it is confirmed on Beale's D'Amico's and Valentini's Air War Italy 1944 - 45 (1996), p. 103. Duke didn't claim it as 109G-8/R5 :=) but the exact designation comes from the fact that we know the victim either Ofw Holstein W.Nr. 200685, Black 3 or Uffz Möller W.Nr. 200023, Black 1 both from 1./NAGr.11. The other was shot down immediately afterwards by Duke. His last 2 kills. So we have combat report, confirming witness statement and confirmation from opponent's (in this case LW's) docus. What else you want? Gun camera film would be nice, I admit, but IMHO fairly well documented case.

Juha

PS On Puhakka's case, Puhakka's combat report, 2 witnesses and the damage on the DB, 20mm hits on the upper skins of wings, with that distance and with fairly low muzzle velocity Oerlikon he had had to aim considerably above the DB to compensate the shell drop at that distance. Puhakka was returning from an interception sortie and was about to land when he saw the bomber and got behind it by a climbing turn, he opened fire while behind the bomber not above it.

 

[stona]

I have read hundreds of combat/encounter reports over the years and there are many instances of aircraft being hit from long range, so I would have no reason to doubt that Duke got in a lucky shot. He was not the only one to do it. I would always be very cautious of the estimates of range given in these reports because gun camera footage almost invariably confirms that most pilots were very bad at estimating this. They were even worse at estimating angle off.
There are far more instances of pilots opening fire at long or extreme range (600-800 yards) followed by comments like "no strikes observed" or "no visible effect". A lucky shot is a lucky shot, by definition rare but not impossible. Nobody in their right mind is going to set their weapons up to cater for a remote possibility.

The range and accuracy of weapons fired on the ground has almost nothing to do with their accuracy when fired from an aircraft travelling in one direction at 300mph at an aircraft travelling in another direction at a similar speed. Frankly it is amazing that anyone hit anything before more sophisticated gun sights were introduced. It's the reason why most didn't.

I would love to see a study on the different arrangements of weapons on WW2 fighter aircraft. I never have done. It is possible that no such study was undertaken because, given the other far more significant variables of air to air combat, it was considered irrelevant and unlikely to yield a statistically significant result. I certainly can't see anyway it would have supported the 2 for 1 opinion of those pilots who ventured their view early in the war.

The RAF didn't adopt armament in the wings, outside the propeller arc without careful consideration. The eight gun fighter was born as a result of careful analysis of bullet densities produced by various installations by the Air Ministry's Armament Directorate. It was discovered that a six gun installation would achieve sufficient density at 240 yards and eight guns at 280 yards.
It was Sorley, in a paper to the Air Ministry's Air Fighting Committee who rejected the idea of a centreline cannon. He did not dispute the effect of a 20mm cannon round on another aeroplane but as he said.

"The basis of discussion, however, is not of the result which is obtained, but rather one of the chances of obtaining the result in the minimum time."

The single engine mounted cannon concept was rejected because in a short burst, all that it was expected their would be time for, the gun would fire so few rounds that it was unlikely that any would hit a vital part of the target.
Sorley continued.

"If the problem of rigid wing mountings for 20mm guns can be solved we should be able to fit four 20mm each with sixty rounds for approximately the same weight as eight machine guns."

He proposed that the Air Ministry should convert the suspended F.10/35 requirement to carry four cannon. The wing mounting problem was not solved as quickly as he would have liked, but this did lead directly to the development of the cannon armed Whirlwind.
It's also why Hawker Typhoons and Tempests were armed with four 20mm cannon in the wings, making them amongst the heaviest armed production fighters of the war.

Cheers

Steve