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Its been long since I last posted something worthwhile, but now I need help in addressing grey areas in a paper I am writing on 'The Science and Art of Main Gun Zeroing'. I know, and please correct me if I am wrong, that the primary criteria for fixing a range for zeroing the main gun of a contemporary MBT is as under:- The ammo used must be the primary tank-killing ammo of the MBT, usually FSAPDS.The size of the zeroing target must be fixed before hand.Based on the dispersion data for ammo used for zeroing, the hit probability must be at least 90%.The M1A1/A2 tanks zero their main gun at 1500 meters. While I do not have the dispersion data for the 120mm ammo used on the M1A1/A2 for zeroing, I do have the zeroing ('screening') target dimensions as under :- I presume that the dia of the 'bull' ( is based on a statistical assurance of at least 90% hits or that each round fired has a 90% chance of hitting within the circle. This brings me to my primary reason for posting here. If I have the dispersion data of a particular ammo variant, say BM-9/BM-12 (at http://www.kotsch88.de/tafeln/st_125mm-ke.htm) can I work out the theoretical minimum zeroing range where at least 90% hit probability is assured? I have tried my hand at working this out but I am not sure if I am right, or if I am missing something. The 'Range Table' (or Firing Table) at http://www.kotsch88.de/tafeln/st_125mm-ke.htm mentions the Mean Deviation figures (in meters) for dispersion for 125mm FSAPDS (BM-12) ammo seperately in elevation and azimuth, in 100 meter range increments. The English language translation of the header row of the table at the ibid web page is attached [attachment=1293:Range Table Header Row.png]. My understanding of the process to work out a zeroing range was as under:- For each range increment in the Range Table, I convert the Mean Deviation to Probable Error (= 0.84535 x Mean Deviation). This conversion factor is applicable for Normally Distributed data. The 50% Zone is twice the Probable Error (= 2 x 0.84535 x Mean Deviation). Again, this conversion is applicable only for Normally Distributed data. The predetermined size of the zeroing target is fixed as 1.2 meters x 1.2 meters (4' x 4') for working out the corresponding 90% Hit Probability zeroing range. So I work out the Probability Factor (= Target Dimension / 50% Zone) I refer to the 'Table of Linear Probability Factors' [attachment=1296:Tble of Linear Prob Factrs.png] and read the corresponding hit probability against tabulated Probabilty Factor value computed above at Step 4. I work out the Hit Probabilities seperately for the dispersion data in the elevation plane and in the horizontal (azimuth) plane. The cummulative Hit Probability at that range is PHit = PElevation x PAzimuth I repeat the entire process (using Excel) for each 100 meter range increment. Refer to the attached Excel sheet [attachment=1294:BM12 Hit Prob.png] Going by my calculation for a 1.2 meter square target, the Excel sheet shows 90% hit probability is assured at 900 meters firing BM-12 ammo from a D-81 tank gun.Therefore, the prescribed zeroing range for D-81 tank gun firing BM-12 FSAPDS ammo is 900 meters. Am I correct in my understanding of the statistical science and procedure for arriving at a zeroing range for a particular ammo-gun combo ? Please guide, comment and advise. Thank you in advance. I have refered to the following books to try and learn the theory:- Textbook of Ballistics and Gunnery, Volume One (Her Majesty's Stationery Office (HMSO), London, 1987).Rheinmetall Handbook on Weaponry, Second English Edition 1982 (Rheinmetall GmbH).Oerlikon Pocket Book, Second Revised Edition 1981 (Oerlikon-Bührle AG, Zurich).Technology of Tanks, Volume One, 1991, Richard M Ogorkiewicz (Jane’s Information Group).Ballistics and Ammunition, Canadian Army Field Artillery Pamphlet, Volume 6, B-GL-306-006/FP-001, 1992.