I think ironglow hit it with the 30-30 velocities,
I live in Minn, and the 30-30 has always been known as a "brush gun", not for it's ability to cut through brush but as it applies to close work, jumping deer in thick cover at close range.
It might sound old school , but your right, the round nose and flat nose bullets have been known for decades to be able to move through grass and light brush. Just as spire points have been known to easily deflect.
As much as they try to improve the BC of the 30-30 buy creating pointed bullets for them, the classic bullet for that gun is a blunt round nose, always has been.
Always tough to loose one, in thick brush like up north you may have actually finished the animal and walked past him 3' away. They can disappear in the thick stuff!
I load 2 bullets for me and the boy, a Nosler Accubond an Barnes TTSX for the power line and wheat field, and Hornady SPFB for the loggin trail.