Hi E Lectric,
Now that I have a comment, obviously not a very popular topic
I'll confess to the motivation and see how you respond (and whether it provokes any sort of reaction.
The numbers for chain designation refer basically to minimum breaking strength, MBS. So a G40 is 40/30 of the strength of G30. G43 is the same calculation (and G70 also - but that's confusing the issue). BBB, I think is an old designation, but is a G30 strength, different link size. (Though G30 and G43 are also different link sizes. G40 is a metric designation thug some imperial chain is G43 but sometimes described as G40.
Now everyone is really confused.
But to return to buying G43 as a replacement for G30 and reducing link size.
G43 has that minimum higher break strength than G30 with that simple relationship of 43/30
But when G43 is quoted for strength it is often sold with the Working Load Limit, WLL, prioritised (and sometimes the MBS does not merit a mention). The WLL is a simple calculation based on agreed safety factors. The safety factor for G43 is 3 that for G30, G40 (metric) and G70 is 4.
The use of a safety factor of 3 artificially 'lifts' the WLL for G43 over G30 - though there is no evidence at all that G30 is any more unsafe (or safe) than G43. I have questioned chain makers who sell marine chain in America and the reasons appear to have been lost in the mists of time but it might be because G43 was originally a Transport Chain (which had a safety factor of 3).
To sell G43 with a safety factor of 3 is quite accepted, its an industry standard for America, but there if one looks at the MBS then downgrading might size and upgrading quality might not result in the same MBS.
There is a trend in Australia to G43 to save weight - I simply wondered if the same might be true elsewhere and if anyone appreciated the implications.
I might add - failure of correctly sized brand name G30 is almost non-existent (so it seems perfectly strong enough - and possible 'over' strength, do not know). Maybe using G43 with a MBS less than the recommended MBS of the G30 does not matter - but I wonder if people realise.