Bulldog,

I own and have shot both. On game you won't see any difference if you do your part.

For nostalgia reasons go with 505 Gibbs. It is a lovely round.

For practicality reasons, go with 500 Jeff.
By practicality reasons, I mean SLIGHTLY EASIER brass availibility
and the number of bullets available in .510".

Feeding issues are NOT an issue if the gunsmith does his job.
Just make sure he sets up the feed ramp for both RN and more pointed bullets
like the Woodleih protected point.

Also, try to pick an action that will give you 4 shots total - 1 in the chamber, 3 in the Mag.

Heaps of 500 Jeff and a few 505 Gibbs have been built in Australia, copies from the
original 500 Jeffrey's that used to be here.

PM me if you want more details.

500 Nitro

PS - I am thinking of selling my Left Handed 500 Jeffrey if you are a Left Hander.