The addition of an RF fuse-setter wired into the fire direction system aboard ship, allied to a programmable fuse, is possible for tubes from 20-203mm and bigger theoretically. Question is whether you have a gun mount that is enhanced by the fitting of such a system in the calibres you mention.

The Mk8 & mod1 will be around another 15-20yrs at least between the UK and South America. Brazil still manufactures 4.5″ shot, but, there aren’t all that many actual tubes in service. Would a gate-fused enhanced-frag round be a boost to Mk8’s limited anti air capability?. Certainly. Is AAW in the BN and RN screaming out for this capability?. No. Is anyone going to be persuaded to buy into Mk8 as a result of a programmable fused round?. Again no!. So, for the market, the rewards of undertaking the work dont offset the costs of doing it.

The French 100mm is a similar story. Clearly the Chinese bought in to the mount and there will be 3.9″ naval guns going to sea for a few years yet to come, but, the French have lost interest and, so the story goes, the Chinese enhanced copy of the French gun didn’t exactly improve on anything!. The decision to cut to a 76mm for the evolved frigates there seems to have decided matters. Without a viable long term mount to serve, despite the apparent suitability of the 100mm tube for an RF set gate-fused AA shell, its a non-starter.