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The ratchet lock also removes the possibility of having it unthread itself during use which is nice if you intend taking multiple shots in a hurry. Big fan of my Oceania!

CCI Segmented Subsonic is absolutely my favourite (they also do a supersonic). Very accurate and very effective. Seems to be good to 150m and runs well in semis.

Just noticed my comment at the top, that was in relation to a genuine Benelli M3 rather than an M4 clone. Inertia vs Gas so may not be a relevant comparison.