Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: moot on April 13, 2009, 05:43:44 PM
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Is the formula that Tony Williams uses to calculate power valid for large calibers like 50mm? As seen on this page (http://www.quarry.nildram.co.uk/WW2guneffect.htm), it works like this:
Damage = projectile weight (kg) * muzzle velocity (m/s) * (1 + (projectile weight's explosive % ÷ 10 ))
I guessed the last one because that's what it seems to be (ignore the black one, it's wrong from a typo):
(http://farm4.static.flickr.com/3599/3439036389_3724925ba6_o.png)
This formula leads to table 1 on that same page of Williams', where that power value's divided by 10 and rounded up, giving e.g. the .303 and MG17, MG151/20 and Hispano, NS37 and MK103 power values of 1 and 1, 16 and 20, and 106 and 99 respectively. If we apply this same method to the 50mm BK5 projectile that's 1530g with 335g explosive content and 835 m/s muzzle speed (as per this page (http://www.quarry.nildram.co.uk/ammotable7.htm)), it gives a power of roughly 280.
That seems a bit large, and somehow a linear addition of (1+HE%) as coefficient to kinetic power doesn't seem natural.
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Just a note: the muzzle velocity of 835 m/s is for the AP round. The HE round will probably be faster, possibly around 870 m/s
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Yep, I've seen a bit over 900 mps too. I'm just curious if the HE factor's scaling is correct..
The page I linked has more details just above that table. oops.. I'd found it linked to directly and never saw those upper paragraphs. For projectiles with a chemical content, we increase this by the weight fraction of explosive or incendiary material, times ten. This chosen ratio is based on a study of many practical examples of gun and ammunition testing, and we will see below that it at least approximately corresponds with the known results of ammunition testing.
:rolleyes:
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30mm Mk103 was a fairly low powered (ballisticly) round compared to the n37, which I think the data shows.
Actually I'm surprised that their isn't a bigger spread between the 30mm and the 37mm. Also is the N37 data for AP or HE? or a combination of both?
What you didn't list (and neither did Williams site) was the 75mm in the B25H, I think that would give you a better framework for looking at the 50mm.
I'd be willing to bet that the 75mm would score well above the 50mm and probably in the 300 mark.
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Gimme .303's anyday.