Spitfire Resources

[dnr]

Great article on a variety of munitions used during the BoB including some data on penetration effectiveness at 200 yards against structure and light armour. Also mentions standard RAF convergence settings for the Spit and Hurricane at the beginning of the battle and later as operational experience was gained (e.g. convergence distances were reduced from 360 to 225 meters (393 yards to 246 yards).
http://www.quarry.nildram.co.uk/BoB.htm

The second article is a good comparative study of munitions effectiveness with some useful charts to help figure out your optimum ammo load.
http://www.quarry.nildram.co.uk/WW2guneffect.htm

[dnr]

Thanks Cheesehawk, I'll read through your link to see what new nuggets are there. Having read through the summary of BoB munitions effectiveness, I did some basic math in order to more fully understand the weapon dynamics between firing at and hopefully hitting another aircraft. When I first started Cliffs of Dover I wondered why the RAF fighers fired such long bursts. The I recently read a history of the Spitfire where the British Air Ministry wanted a stable gun platform that could deliver 2.5 seconds of sustained fire at a bomber. The eight gun .303 set up was considered sufficient to cause the failure of the target aircrafts systems. In reading the data in the previous links I now understand why this was. If you read the data below, it's clear that anything less than 2.5 seconds, the chance of penetrating 4mm armour plate was very slim. Also Cliffs of Dover tracks our hit percentage which is critical in estimating your chances of downing an aircraft with a well placed burst. I've gone with 5% (although I checked my stats and am now up to a whopping 6%). Of these, only 33% are expected to penetrate the aircraft skin and structure, and of these only 6% are expected to penetrate the armour plate. Based on your burst duration, and how you set your gun configuration, you might be surprised by how little effect you really have on that target of yours. I've based my calculations on six guns firing .303 AP. I have my #1 and #8 guns firing incendary, tracer and observer rounds

.303 AP Penetration @ 200 Yards
Column titles left to right:
(1-Burst duration in seconds) (2-Total AP rounds fired 6 x guns) (3-Gunner accuracy @ 5% hit ratio) (4-33% penetrate aircraft skin) (5-6% penetrate 4mm armour) (6-Length in feet of bullet stream) (7-Total rounds per liner foot)
(1) (2) (3) (4) (5) (6) (7)
0.25 30 1.5 0.495 0.0297 607.5 0.049
0.5 60 3 0.99 0.0594 1215 0.049
0.75 90 4.5 1.485 0.0891 1822.5 0.049
1 120 6 1.98 0.1188 2430 0.049
1.25 150 7.5 2.475 0.1485 3037.5 0.049
1.5 180 9 2.97 0.1782 3645 0.049
1.75 210 10.5 3.465 0.2079 4252.5 0.049
2 240 12 3.96 0.2376 4860 0.049
2.25 270 13.5 4.455 0.2673 5467.5 0.049
2.5 300 15 4.95 0.297 6075 0.049

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[dnr]

Cheesehawk,

Since changing my convergence from 437 yards (400 meter setting in the plane loadout) to 230 meters (250 yards) and setting my sight properly, my hit percentage has jumped to 17%. Close in engagements and longer bursts have had a noticible effect, particularily with bombers. If you re-calculate the numbers, whereas before a 2.5 second burst with a 5% hit ratio would result in 15 rounds hitting the target, 4.95 rounds penetrating the skin/structure and only .297 rounds penetrating the armour (virtually zero) then compare that with the new convergence setting with a hit percentage of 17% (this is not a new average, but the results of one mission), then 51 rounds will hit the target, 16.83 will penetrate the skin/structure and 1.0098 rounds will actually get through the 4mm armour plate. Odds are still not in your favour, but the numbers do demonstrate the effect convergence has on the potential outcome on an engagement.