The hollow point NOE provides with that mold is too small for subsonic expansion, you are right to be concerned about penciling through. (I believe they've redesigned it in the latest run, but I'm guessing that's not what you have.) Your comment about reduced accuracy with soft alloys mirrors mine; I'm using the 300 in the AR15 platform, and accuracy is much better with a ww alloy around ~10 bhn or so than with soft lead. I made a larger set of pins for that bullet for a member on the 300 Blktalk forum (user name bangbangping if you want to ask him about it); I sized the pins for good expansion with coww equivalent and to drop easily from the mold.
In this application, for deer hunting, it's better to have too much expansion than not enough, but also make sure the remaining bullet shank is heavy enough to continue through the animal if the nose fragments off. My best subsonic/suppressed hunting bullet performance on deer has been when the nose fragments off in the chest cavity, causing significantly more organ damage, and the base passes on through the far shoulder. The main wound track is generally about golf ball size through the vital organs, with some smaller tracks as fragments move out laterally, and the shank pretty much makes a pencil hole through the far shoulder bone. As a rough rule of thumb, I want the remaining shank to be ~2/3 the original bullet weight. Performance wise, that gives you essentially a subsonic Nosler Partition.
I will also say that good subsonic hunting bullet performance is a lot easier to achieve in a 35 caliber than in a 30 caliber or smaller. That is what led me to build a big brother to the Blackout in .358 bore, also in the AR15 platform.
Larger hollow point in NOE 247 for better expansion:
http://i24.photobucket.com/albums/c2...0147%20HP2.jpg