the Jagd IV had the 75mm Stu.K.42 L / 70, which fired the same ammo as the Panther's 75mm Kw.K.42 L / 70. That means at the PzGr.39 projectile was moving at 935 m/s and could punch through 89mm of 30° armor at 2000m.
The frontal and side armor was very comparable to the Panther. It would be a Panther w/o a turret. It would deadly at long ranges, but a fast moving T34 or M18 would be the bane of the Jagd IV since it could not traverse fast enough to follow. I seriously do not think most people comprehend how difficult it is going to be not having a turret. Go spend some time in the M3/75mm and see how much fun it is to try and traverse the entire vehicle to stay on a moving target. Remember, that means if you are able to keep up you are turning your side armor to the enemy's front.
As I said in my first post, it would fun to have but I think the Su-100 would be a better "first" for a turret-less AFV in AH simply because of the numbers and usefulness, followed closely by the StuG III.
