Yes, halleluyah and thanks !!! I thought it would be similar to 10T-13, 10T-15 ;P only with more scales (they are described in manual, they are for firing on reduced charges) and it's in fact quite similar, being "moving cross" type, T-34/76 like gunsight.
But.... well it says it's CT-10.. but it seem to be scaled for much longer than 900m.... It's about 620m on the scale for full charge shot (right) but on picture then use the reduced charge (??) left scale... have to check in ISU manual, can't remember which is which. Then all the info from internet (about CT-10 being 900m sight, and for longer shots the PG-1 had to be used) is just plain wrong ?
Can you post whole picture/page (I would like to see the CT-18 too... eeee would like very much - isn't CT-18 a sight for ISU-122 ??), and best would be of course to have the full manual (I read Russian a little bit). Then the reticle and ways of laying the gun and shooting are described.
BTW if it's really CT-10, then shooting at 5000m would be EXTREMELY difficult, not only it would take ages for the shot to reach the target, not only the 152mm howitzer is not most accurate weapon, but also the CT-10 itself has only x2 magnification (and 18deg FOV) and the target would be very small.... The target would be not that big (would be a dot in fact) at 3000m, not even mentioning that the instruction probably doesn't even allow firing 152mm short howitzer at tanks from such large distances - other that with HE shells. Maybe it's really 300m but misprinted ???
It's possible that you can't reply to yourself (post twice) on this forum, and also can't post too soon after last post (1 minute?) so maybe this is the problem with posting ? But why your posts from several days ago (not one) didn't show up, I have no idea
P.S. According to the manual (the one we had before, without pictures), my crude translation:
The first scale from left, "scale named above ДГ, below ПЕРВ / ПУШ is ment for steel long range fragmentation/HE grenade OF-540 on first charge AND for AP shell with tracer" (so at least this is cleared).
But the fact that the scale is joined, doesn't mean that both shells have identical ballistics - often a conversion table was used for firing some kinds of AP ammo - in T-34/76, T-34/85 and IS-2 too. You had to learn very fast table reading, or... just have it in your memory, in the heat of battle, to aim and shoot fast and effectively. On this picture is seem they use the scale directly (3000m range, line set to 30).
Second and third scales from the left, "scales named above БТ and ДГ and below ГАУБ / ПЕРВ and ГАУБ / ПОЛН are ment for firing on first (reduced) and full charge with anti-concrete T-530 shell and steel long range fragmentation/HE grenade OF-530 and Iron cast fragmentation/HE grenade OF-530A."
Hmm, the T-510 in the manual is probably misprint, as the shell is actually named Г-510 (and the scale - ГАУБ). Which raises interesting issue, that the manuals (and labels on pictures in them) are not error-free, and common sense/comparing with other sources is advised
Now, the grenades on mentioned for the two right scales have same weights and with the same charge achieve same MVs, also have probably same or similar ballistic coefficients, so using the same scale for all without conversion tables is likely.
The OF-540 grenade and BR-540 AP have same weight, but very different ballistic coefficients !!
edit: of course they have DIFFERENT weight so also different muzzle velocities... my error
The scale for my best knowledge can't be used directly for both, because of different ballistics !! So maybe the "anti-tank shell with tracer" mentioned in this 1950s manual is the BR-540B APBC which has ballistic cap and ballistics very similar to OF-540 - and this is why the scale is set at 30 for 3000m target.
edit: again I see a problem, if BR-540B is still 48kg shell and OF-540 43.6kg shell, then they can't possibly have same muzzle velocity so the scale can't be correct for both... even if ballistics are the same. Or something was done with that, like increasing BR-540B charge to get same muzzle vel. as for HE shel... but could the barrel withstand that ? Decreasing OF-540 muzzle velocity to same as BR-540B ? But that would reduce the range, and I think its very unlikely solution (90% of fired shells are HE, so too much tables/manuals/gunsights would have to be replaced).
In case of BR-540 (pure AP) used during the war, the scale would be set at much more than 30 to reach 3000m (the exact value would be read from tables) or the sight looked little different in war-production ISU-152s and there was a separate scale for BR-540.
But I think the first is true (scales same, conversion table used) as BR-540B was already on mind for future use probably, and BR-540 was thought to be a temporary solution.
So much of my comment to this. I wanted actually try to make a gunsight texture (looking and working like 10T-15, so similar to T-34/76 sight but incorporating the 3 scales mentioned above, scaled accorindgly to sight zoom and FOV) if we didn't find the picture of CT-10
now I don't have to fortunately
Ami
P.S.2 I would like very much to see the full manual, if it's possible
Maybe some info about ammo can be found there ?
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