Ok, with all the discussion on the P51 with 4 or guns, with some claiming better performance. I did some simple tests.
**Method**
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All tests done in offline mode with 25% gas with all the ammo used up (fired before engine started). No flaps, no ord, no WEP.
Test 1. Acceleration.
Head N from field 1. Climb to 5600 feet (a1 elev is 5000 feet). Engage auto-trim (level) Adjust throttle untill 120 IAS reached and is stable. Check headind is due North. Engage 100% throttle at full RPM and start timer. Time at 200 IAS, 250 IAS, 300 IAS.
Test 2. Climb Rate.
From Feild 1 head to 300 feet at grid loc 12.8.1. Set auto-speed to 180. Set course due West. Engage auto-climb and throttle back untill ROC is 0 (and stable) and plane is level at 300 feet. Engage 100% throttle, full RPM, and start timer. Stop timer at 15,000 feet.
**Results**
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Test 1.
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120-200 IAS. 6 guns = 16 secs
200-250 IAS. 6 guns = 35 secs
250-300 IAS. 6 guns = 106 secs
120-200 IAS. 4 guns = 16 secs
200-250 IAS. 4 guns = 34 secs
250-300 IAS. 4 guns = 104 secs
Test 2.
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4 guns 300-15,000 feet = 4mins 11secs
6 guns 300-15,000 feet = 4mins 16secs
In test 1 the extra weight of the 6 gun configuration contributes 2 seconds extra acceleration time from 120 to 300 IAS @ 5,600 feet and only 1 second from 200-250 IAS, and none from 120 to 200 IAS. The acceleration difference is 3.03% (120-300 IAS).
In test 2, the 14,700 feet climb took 5 seconds longer due to the extra weight of the 2 extra 50 cal machine guns.
**Discussion**
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The ammo was fired prior to launch to determine the actual difference in performance (climb and acceleration) that is due to the weight of the 2 extra .50 calibre machine guns in the 6 gun set up. This ensured ammo load out is not a factor.
This test has proven the the 4 gun armament option of the p51-D does afford marginally better performance over its 6 gun counterpart. The accleration to 300 IAS took only 2 seconds longer for the 6 gun variant. This, in practice, wouldnt afford much of an advantage, as acceleration of this length is not often put to use. The crictical accelearion period from near stall to approx best cornering speed (240 IAS) is only 1 second in difference. Due to the P51s comparatively low acceleration rate in the current AH plane-set, the P51 is best flown at speeds of no less than 240 so as not to rely on its poor acceleration.
In terms of climb, the 4 gun variant offers a 5 second advantage in the 300-15,000 feet climb test where it took 251 seconds in total, offering a small 1.95% climb advantage. As the p51 is a reletively poor climber in AH, relying on its sustained climb rate would be foolish. As such it should be flown fast so it can zoom to or run to safety. Again the 4 gun option fails to offer any realistic advanteges over the 6 gun version.
The 33% loss of firepower should translate roughly into 33% loss of lethality. As enemy planes harldy ever just sit still when being shot at, the more firepower you concentrate on a target in a given time period the more lethal the gun package becomes - and visa-versa. The 4 gun version would effectively remove any hope of a snap-shot type kill, so a sustained burst of 33% more length would be needed to down a plane.
The advantages offered of minor acceleration (3%) and minor climb performance (2%) is far outweighed by the loss of firepower (33%).
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S p a t u l a 
=357th Pony Express=[This message has been edited by Spatula (edited 02-25-2001).]
