View Full Version : .303/.50/20mm question

08-12-2005, 03:32 AM
I wondered what ammo makes some planes of different marks shake a lot more than others. The question i have is why does .303s seem to have most recoil? More than both .50s and even cannon ammo.

Test planes:

Spitfire Vc (2 cannon):
with mg only: lot of shake/recoil
with cannons only: minimal/almost no recoil

Spitfire VC (4 cannon)
with all cannons: minimal/almost no recoil

P-40 B/C
all guns (four .303 in wings and two .50s in nose): shake/recoil

P-40 E
all guns (six .50s in wings): no recoil

Hurricane mkI
all guns (six .303s): shake/recoil

Hurricane mkIIc
all guns (four 20 mm cannons): minimal/almost no recoil.

Specially in Spit Vc test the results are clear; four .303s produce much more recoil than four 20 mm cannons. Also the P-40 test shows that for some reason four .303s in wings and two .50s in nose is a more unstable configuration than six .50s in the wings.

08-12-2005, 03:41 AM
Didn't really checked... but I have noticed that if your MG is jammed, it is very hard to make correct burst. Also 4x20 Spit seems to have noticeable recoil effect. I remember one Hurricane veteran that was talking just how powerful were .303s... he said literally "when I started to shoot from MGs, it seemed that my airpalne stopped in mid-air for a second...".

Anyway I like nose armament much better.

08-12-2005, 04:02 AM
If I had to guess, the issue is this:

When dealing with multiple machine guns and cannons, all of which are off center of gravity, these factors need to be considered:

1: The amount of recoil produced by each shot from each gun would be affected by the position of the gun. The further from the center of gravity, the more the gun will effect the plane. If you want to do a home brew test of this, try the following: Fire any pistol using the proper techniques. Then, hold your arm as far out to the side as it will go, and fire a shot forward. It'll yank you around. If you use a large enough caliber round, it may even seriously hurt you.

2: The rate of fire of each gun effects the amount of force the gun puts of the airframe over a period of time. I imagine that ROF is in large part why cannons seem to have less recoil, even though on a single round basis, they don't. To do a homebrew test for this: Get ahold of any automatic fire capable weapon. An m-16 a1 works well, as well as many others. Fire several single-shot rounds at the target. Next, empty a full magazine at a target on automatic. If you know a gunsmith or something, you can even experiment with controllability at different fire rates, there is a HUGE difference.

3: When dealing with mutliple weapons, especially when they are far from center of gravity, when exactly each round goes off will effect the recoil. If say you have 2 .30 cal rounds go off (assuming equadistant weapons) at exactly the same time, the overall effect will be pushing the plane straight back and a little nose up. If they go off at different times, the effect is instead that it pushes one wing back and up, then the other, causing the plane to oscillate.

So, with multiple unsynchronized automatic weapons firing far from the COG, all with slightly varrying rofs, you can see just where the differing recoil comes from.

It is possible that the values are modelled incorectly, however, I don't claim to know more about WWII era weapons and how they affected WWII era airframes than oleg.

08-12-2005, 04:15 AM
I stand corrected, however the recoil effect is different, cannons seem to sway more but not so much shake. Try this: fire just one 'bop' with Spit Vc four .303s and then one 'bop' with four cannons. It shakes a lot more with the .303s.

Specially the P-40 test raises my eyebrow. Does the P-40 B/C have a different wing than P-40 E? Beacause the six .50s are further out on the wing than the four .303s and yet the P-40 B/C shakes more.

08-12-2005, 04:36 AM
Shake is just a graphical effect, so I wouldn't worry about it.

The sway, on the other hand, does seem to correspond with the actual momentum output of the guns, and their distance from centerline. However, aircraft stability plays a huge factor in sway as well. Light airplane, short tail, big vertical stabilizer=good.

08-12-2005, 06:23 AM
Haven't U tried ki-43, val or g50 and cr42 yet olli? the craprides of your choice?

The first two have 2 peashooters in cowling and val has one peashooter backwards.
The italian birds have heavy mg's in the cowling.

My guess is that the two peashooters will likely rock more because it's how i belive they are modelled.


08-12-2005, 06:55 AM
also the Sturmovik shakes a lot with only 2xSkas firing.. would say 1C mixed it somehow.