The text above the table shows the direct fire distance, the distance for which the shell trajectory does not surpass the height of the target, for three target heights: 970 meters for a 2 meter target, 1120 meters for a 2.7 meter target, 1180 meters for a 3 meter target.

The columns are as follows: distance (in meters), sight settings (using two different kinds of sight scales), trajectory height (in meters), two columns for correction (for drift and wind), the amount of height a single division on the sight would change, angle of aiming, angle of falling, impact velocity, time in flight, and, finally, two columns for average deviations: vertical and horizontal.

Nothing special, precision-wise for the BR-471B round. Average dispersion of 30 centimeters in each direction at 1000 meters is more or less consistent with previous tank guns I have shown off. The table for the BR-471 round is the same accuracy-wise.

The direct fire distances for the HE shells are the same, but there are a lot more columns. The first six after distance are for setting up various sights. The seventh is for trajectory height. The next eight are for corrections for even more things, including atmospheric conditions and temperature. The next one is the change in distance that will occur with one one-thousandth change in the setting of the sight. Next is short bracket. Next is the aiming angle. After that, the impact velocity and flight time, same as the previous table. The remaining figures are for average deviation, but there is a new column: average deviation for distance. This is necessary for indirect fire.

The high explosive OF-471 and OF-417N shells manage to be even more precise, with an impressive dispersion of 20 cm vertically and 30 cm horizontally. That is the lowest figure of any gun I have seen a table for so far.

Most interesting ... do you think you can translate the Cyrillic on the tables. I can just read enough to know that "Direct-Shot" (equivalent to point-blank or battlesight?) range is 970m for a 2m target and 1180m for 3m.

ReplyDeleteSure, no problem.

Delete30cm x 30cm under soviet defintion of pattern using the radius only, would equal a german rectangle of 60cm x 60cm with the same 50% confidence level.

ReplyDeleteTotal pattern at 1000m would be 2.4m by 2.4m for the D25 using BR-471B APBC, which is 140% larger than the total pattern size of the 88mm L71 Pgr39 at this range: 1.2m x 2.0m.