The CRPF is simply a hybrid of the same push feed bolt head that has been used on model 70's since the conversion from CRF back about 1964.

It uses the same exact bolt and extractor as the push feed design but with two modifications. The bottom of the bolt is relieved so that the rim of the cartridge can slide under the extractor and it uses a fixed ejector instead of the plunger used of the push feed bolt.

Basically it blends the benefits of both designs into one single bolt. You got controled round feeding but with the benefit of being able to drop a round into the chamber and still be able to close the bolt like on a push feed. You can't do this on the regular CRF bolt design.

To be honest I don't know why this design wasn't brought about many many years ago.