Here are two New Home bobbin cases. The solid bobbin is a New Home, the other a 301. As you can see the 301 fits nicely in terms of diameter. In the second photo you can see that the 301 is just slightly thinner than the New Home, it sits in the bobbin case with a little room.. The inner holes are almost identical.
If you give me a day or two I can test with the 301 bobbin in the New Home machine and report back.