Military Arms Channel on youtube does some pentration test on the 308 Winchester, 7.62×39, 5.45×39 and the 5.56mm.
In the video the tress are said to by 3 feet in diameter. I think that statement is in error. Its probably more like 3 feet in circumference instead of diameter. A simple way to convert circumference to diameter, measure the circumference then divide by 3. If you want to be exact, measure the circumference and then divide by 3.14. For most intents and purposes for this type of video, divide by 3.
I was surprised the 5.45×39 penetrated the tree while the other calibers did not.
What “really” surprised my was the lack of penetration by the 308 Winchester. But then again, shooting from a bullpup the 308 may not have reached terminal velocity. I wonder how the 308 would have done out of a 20 inch or longer barrel, or from a bolt action rifle instead of a semi-automatic.
Why did the 5.45×39 the tree, while the 7.62×39 and the 5.56mm did not?