The DCRA 7.62 mm conversions were sent back with:
1. the C.Mk3 .303 calibrated sliding rear sight
2. the .303 extractor
3. the .303 magazine
If you are using the rifle as a single shot, the .303 extractor works fine, it will not eject the cartridge however.
.303 extractors can be modified to work better for ejection purposes- but a .308 extractor is a much better tool.