General rate of German MG Fire

[bcnewbur]

I read a letter (I think in Bloody April) indicating Richtoften (sp?) spent 150 rounds before his victim flamed. It was apparently from 20-50 yards out. Can someone tell me how long in terms of seconds that would be if continuous? or even in three second bursts.
Aircraft should not matter but it was an Albatross.

[Alkali Jones]

Hey bcnewbur,

Wikipedia says four hundred and fifty to five hundred rounds per minute. That is about what I've read in other places. Four fifty RPM is seven and a half rounds per second. So, one hundred and fifty rounds would be about twenty seconds worth of firing... right?

Dan S

[RAF56_Ball]

Except with two guns, the time would be halved.
900 RndPM, = 15/sec, or 10 seconds.
Good grief. I am up at 1 AM doing math. Am at work, but still, is quiet.
Say good night, Gracie. "Good night, Gracie!"

[Alkali Jones]

Hey RAF56 Ball,

Good point! Over night, I realized that the "interrupter gear" was not called that for nothing. So of course, every time the blade came in the way, the gun was prevented from firing for a brief interval.

Assuming continuous firing, it would take longer than ten seconds to fire all one hundred and fifty rounds. How much longer? I have to think about it some more.

Hey bcnewbur,

Do we know which Albatross? Which engine? I think we could figure this out.

Dan S

[bcnewbur]

Book Bloody April, around page 25-30 mentions Richtofens Albatross, Likely a Mercedes DIII

[John McKenzie]

Note that when the blade is in front of the gun , ( appx 2200/ 2650 times per min and very much dependant on motor type ) , the gun is " interupted or prevented from firing " , ONLY IF it was going to fire at that particular point in time , in any case .

Dave Watts showed from examples of motor & Gun speeds , that the best setting for rate of fire was about 450 Rounds per min , which gave the least interuptions and an actual rate of fire at something less than that figure ,..maybe 380/400 max. perhaps .

There would be an " Optimum" motor speed to Gun firing rate , combination.

If the gun is set to fire at a higher rate , then , in conjunction with the motor revs , an even Lower fire rate is the probable outcome , than when set at the (appx) lower optimum due to the worsened synchronisation of motor rpm to gun rpm .

The figures above are VERY MUCH guesses / taken from Memory ....& subject to correction .

Someone could probably give a Link to that older thread I expect ?

[kristjanr]

Originally Posted by Alkali Jones

Hey RAF56 Ball,

Good point! Over night, I realized that the "interrupter gear" was not called that for nothing. So of course, every time the blade came in the way, the gun was prevented from firing for a brief interval.

Assuming continuous firing, it would take longer than ten seconds to fire all one hundred and fifty rounds. How much longer? I have to think about it some more.

Hey bcnewbur,

Do we know which Albatross? Which engine? I think we could figure this out.

Dan S

Except the "Interrupter gear" is a misnomer, "Synchroniser gear" is more accurate. An interrupter gear literally disables the mechanism of the gun when an obstacle is in the way. Such gizmos were used on some WWII bombers (dunno if they had them during WWI) to prevent eager-beaver type turret gunners, drunk on their own adrenalin, from shooting pieces off of their own aircraft.

The synchroniser gear used in WWI aircraft did not prevent the gun from firing when the propeller was in the way, it was the other way around. IIIRC the Maxim gun was ine effect turned into a semi automatic. The pilot did not fire the gun, when he pressed the trigger button on his control column he simply enabled the synchroniser. It was firing impulses from the synchroniser gear that actually fired the gun a set number of times each time the prop blades were out of the way. Thus the rate of fire depended on engine speed and how fast the gun could cycle a single round. As the engine sped up the gun would get closer and closer to it's maximum cyclic rate which could not be exceeded. For an unsynchronised German Maxim this maximum rate of fire is usually quoted as being 300-350 rpm for an unboosted gun and 450-500 rpm for a Maxim fitted with a muzzle booster. To make things even more confusing the rate of fire for a synchronised gun could vary as the engine speed increased so paradoxically the gun's rate of fire could, for example, be higher at 800 engine revolutions than at 900 revolutions.

Unless you speed up the mechanism by adding more powerful springs, installing a muzzle booster, shortening movements in the lock mechanism, etc... the synchronised German Maxim gun could not fire any faster than 450 rpm without reengineering. This was perfectly possible, the Finnish M-32/33 models of the Maxim and the post-WWI Soviet PV-1 aircraft gun were basically performance enhanced versions of bog standard Maxims and they had a cyclic rate of 800 rpm. Of course as you boost speed you also decrease reliability since neither the Russian/German Maxims nor the British Vickers (modified Maxims) of 1914 were designed to operate at 800-1000 rounds per minute. So perhaps the fact that the Germans never boosted their guns to these cyclic rates had something to do with the fact that they figured the contemporary synchroniser gears introduced enough unreliability without also overtaxing the gun's lock mechanism? Other WWI guns, like the Austian Shwarzlose, could only be successfully synchronised at certain engine speeds. I never quite understood why this was but it had something to do with the Schwarzlose's idiosyncratic lock mechanism. KuK Fighter often have prominent bullet strike sensors on the prop blades connected to a big warning light on the dashboard and a very prominently placed RPM gauge for this very reason. Gas operated guns were also hard to synchronise. Raymond Saulnier failed in his attempts at synchronisation because he used a gas operated gun and gas operated guns have a much more uneven interval between shots than the Maxim and a constant firing interval is obviously important when firing through the propeller. It also helps to have high quality ammunition and the Maxim's recoil operated mechanism was apparently more consistent and tolerant of crappy ammunition.

Eventually people switched to guns that took things like ammunition quality out of the equation and because they had simply reached the limits of what you could do with recoil/gas operated weapons. This included the motor driven Gebauer M.1918 that saw use on Hungarian Fiats and Re.2000 fighters until well into WWII while the Germans went for electrical synchronisers actuating electrically fired and electrically loaded guns like the Rheinmetall-Borsig MG.131 and MG.151.

There is a nice little explanation here:
http://www.777studios.net/Screenshot...chronizers.pdf

For those wanting more details I recommend Harry Woodman's "Early aircraft armament":
Early aircraft armament; the aeroplane and the gun up to 1918.: Harry Woodman: 9780853689904: Amazon.com: Books

[bcnewbur]

Gee I wish you had given a bit more detail.

Thank you, so we can say about 400 rounds/minute/60 sec = 6.6 rounds/sec

Therefore 6.6 x 6 sec burst = 39.6 rounds per 6 sec burst

150/ 39.6 = 3.78

Therefore: @ 4 - 6 second bursts required for 150 rounds.



Anybody disagree?

[kristjanr]

Originally Posted by bcnewbur

Gee I wish you had given a bit more detail.

Thank you, so we can say about 400 rounds/minute/60 sec = 6.6 rounds/sec

Therefore 6.6 x 6 sec burst = 39.6 rounds per 6 sec burst

150/ 39.6 = 3.78

Therefore: @ 4 - 6 second bursts required for 150 rounds.



Anybody disagree?

What can I say? I'm on holiday in rural Germany had noting better to do.

Basically, and depending on engine speed, the cyclic rate of a synchronised and boosted pair of lMG 08/15 typically used on German fighters of the 1916-1918 period would have varied between 2x300 and 2x450 rpm. So, depending on engine speed and with both lMG.08 guns working, that's between 50 and 75 rounds on target during a 5 second burst from Richthofen's Albatros D series or his Fokker DR.I. A Fokker Eindecker with a synchronised but unboosted MG 08 would have had a much slower cyclic rate. If that same Eindecker was armed with a synchronised Parabellum it would actually have had a significantly better rate of fire than if it had been armed with a boosted MG.08 since the cyclic rate of the unsynchronised Parabellum was around 700 rpm. Theoretically you'd get almost as much firepower on average out of a single Parabellum as you'd get out of two lMG.08s.

Assuming Richthofen's Albatros D series or his Fokker DR.I:

• 300 rds/min x 2 guns = 600 rds/min -> 600/60 = 10.0 rds/sec:
  i.e. 15 seconds for 150 rds
• 400 rds/min x 2 guns = 800 rds/min -> 800/60 = 13.3 rds/sec:
  i.e. 150/13.3=11.2 seconds for 150 rds
• 450 rds/min x 2 guns = 900 rds/min -> 900/60 = 15.0 rds/sec:
  i.e. 10 seconds for 150 rds

[bcnewbur]

Agreed. Checking to see if anyone noticed I used a single gun. You passed. Sorry to hear you only have machine gun math in your life right now.