I don't need much of a reason for a new rifle but I usually come of with some kind of need (real or imagined) to justify whatever the latest urge happens to be. Right now I have an itch for a 500 Jeffery. Here is my line of thinking:
I'm probably not going to africa anytime in the near future but being an experienced handloader I can load it to whatever power level I want. One can use light 50-110 winchester bullets for fun shooting or deer and load it up to higher power levels for moose and big bears here in Alaska where I live.

Of course I already have other rifles that do those things well but a 510 big bore sure would be fun!

I can spend a lot of time in those boring staff meetings at work thinking about important stuff like this!

Those same and better arguments can be made for the 500 A-Square and even the 500/470 Mbogo.

Only if you are a nostalgia freak, and prepared for possible and very likely long suffering, should you choose the 500 Jeffery.

I might build a 500 Jeffery someday, but only as a stunt.

470 gr cast bullets at 1100 fps are fun, and if you throat it long, you can push 50 bmg milsurp bullets 2200 fps, and only burn 1/2 the powder of a 50 bmg.

I would concur that unless you just have to have a 500 J, the 500 A-sq and it's ilk make way, way more sense. Easier to get the round to feed, brass is 1/2 the price, and it has enough powder capacity.

the 500jeffe is probably the hardest .510 sporting round to build a rifle around. Better/faster/cheaper... get a cz550 is 416 rigby, rebarrel to 510wells, 500 a2, 500 Mbogo... and keep going.

jeffe

500A2! Dont waste your time on the 500 Jeffery.-Rob

I think the 500 Jeffery is fine to build and in knowledeable hands, easy to make. I have one by Sterling Davenport with a staggered box magaxine with 3down and 1 up. It could easily be made to take 4 down with a new floorplate. It will cycle as fast and sure as any rifle I own and I own a few.