AFAIK, all B-78 rifles were issued with the extraction/ejection mechanism set up for full ejection.
If your rifle either doesn't eject, or has some of the parts missing (ej hammer washer, ej hammer sear, ej hammer spring & guide, & the ej hammer) - them someone has disabled the ejection feature, either deliberately via parts removal, or accidently.
If you have all the parts, the B-78 Field Service Manual describes how to reassemble the EJ properly.
.