Well this is really hard to discribe for me. While i use english alot, i lack alot technical terms, aside from those i use in my field of expertise. I took a glance over the postings, but i havent seen if this has been mentioned.
Now i have not hat may sources to confirm, its more an impression i have when i look at pictures and drawings of the BA-6 in comparison to your model. Or better looking at the 3d prototype, i dont really have the same impression when looking at the 3d drawing. The proportion of the turret to the hull seems to be slighly off, i have the impression that the turret can depress the gun any further than shown on the picture (not even reaching 0° of "depression").
Looking at the pictures in ""Zaloga - Soviet Tanks and Combat Vehicles of World War Two, page 93", the turret seem to be smaller (or the vehicle seems to be bigger).
The picture here is similar
https://www.the-blueprints.com/blueprints/tanks/ww2-tanks-soviet-union/15763/view/ba-6/ .
Even the Wikipedia article (although i don't really like using Wiki as a reference;
https://en.wikipedia.org/wiki/BA-3/6) , make me think your is either to "big" or not placed corretly.
This might be just an issue with the picture as well, but i wanted to share my impression.
A drawing of the BA-6 and the 3d Prototype for comparison.