I am looking to reload this cartridge and the only mordern information I can find is in the Asquare reloading manuel.
Can anyone help and has one one wxperience in reloading this cartridge?

Nickudu's loads can be found in the reloading pages. There is some recent discussion of this in the big bore section under ".505 Gibbs Ballistics." Please report back with your results.

Hey !!
Here are some tips:152 gr. of imr-4831, behind a 600 gr. barnes original (i think),that should do 2578 fps,,and figure almost 9000 ft/lbs of power !
There was another load of which Nickudu got 2260 fps with a 700 grain bullet, and i think it was with the same powder,,that's 7940 ft/lbs !
But o0ne thing. This cartridge has so much capacity that it should do over 2600 fps with both 570 gr. and 600 gr.And with 525 gr. this cartridge with mod. case should do 2700 fps, easy !Figure 2300+ ,and 700 grainers. Wth the right powder i think this cartridge could do 2400 fps as a max with 700 gr. bullets.
I have to explain. as again i ask you to check out the load data on the .500 A2 which has a max load with 26 inch barrel,12 twist , that could send a 700 gr. out to 2400 fps,,,BBBUTT this cartridge has only a water capacity of 152-153 gr.
While the huge .505 Gibbs has a water capacity of 176-179 gr. depend on the brass of course. But with Horneber brass .505 gibbs you wont be disapointed,,their brass is splendid. f.ex Ulrik owns a rifle of enormous power,,namely the .577 T-rex and when he uses horneber brass it takes 225 gr. of water compared with A-squares own cases,which take 212 gr.And one could reload it 10-12 times i've heard. By the way i heard someone owned a .510 gibbs and got 2700 fps with 600 gr. bullets, and 2750-2800 fps with 570 grainers !!That's awesome dude !!
I hope Horneber company will stay alive veryyy long, so we can continue enjying exellent quality and products. So go to Horneber and order cases,,ans you will have some impressive numbers on your chrono !
This will sound very stupid, but i have never tried horneber before so why do a think so good about his products ?Well ,,all of those i know have been using Horneber brass ,says it's the best there is !(Ulriks loads are supporting that Hypothese )