TEW, on 29 April 2012 - 11:48 AM, said:
I too have a SOS board and a post HERE
. My board sounds similar to Centurion's example and gave a target which I worked out to be 3000 Yds away and 37 metres lower and obviously out of sight, possibly even during the day let alone night or fog.
With the given range and angle of the Vickers plus the height difference it seemed to me the rounds were travelling in an arc and then dropping out of the sky onto the target 3000 yds away. Not quite sure how effective this would be, maybe a silly statement but aren't they just 'falling down' without any velocity?
Using the Range Table for .303 inch Mark VII ammunition (which WWI Vickers guns would be firing) in Appendix I, Part IV of Text Book of Small Arms 1929, the residual velocity at 3,000 yards is 300 feet per second. This gives an energy of 34.78 foot pounds, not much less than the figure of 58 ft.lbs. which was the energy figure considered for years to be necessary to cause a fatality. This level (58 ft.lbs.) is still achieved at 2,600 yards when the residual velocity is 400 fps.
To achieve a range of 3,000 yards the elevation of the gun is 834 minutes (13 degrees 54 minutes) and the descending angle of the bullets at 3,000 yards is 2009 minutes (33 degrees 29 minutes), so hardly falling out of the sky!
This Range Table was determined by experimental firings at the School of Musketry at Hythe. It differs very slightly from the Range Table for the Vickers in various Training Manuals but "has long been found satisfactory in use, particularly with the Vickers gun. The differences between the two tables lie well within the tolerations for the variation of ammunition".
Incidentally, time of flight to 3,000 yards is 15.1 seconds.