Impossible to answer without knowing maker's name.
No sn data in the pubic domain.The H&R model 306 ultra semi-auto rifle was made from 1965-1977.
Yes, one was made with that sn.
No sn records.
Browning.com has sn data under customer service.
If you can find published sn data, that would let you know.
Proofhouse.com has sn data.
One of many models made by H&R
Herbert Schmidt.
No published sn data.
H&A most probably
10-100
Old gun catalogs can give you an idea