I have a 510 Wells, which basically is the same as your 500 A Square, 460 Weatherby taken up to .510 caliber. I had a Ruger Magnum in 416 Rigby that was useless for accuracy, so called up Brian at SSK and asked what can we do with this thing, he suggested he had 510 Wells reamers, so off we go. The rifle is quite nice looking, but it is useless to me as it is so damn big, 11 lbs no scope...... with 24 inch barrel it is just a beast of a gun. And it knocks the crap out of you. I am not recoil shy, and at one time was shooting 8000++ rounds a year big bore 416 to .500 caliber doing load data, pressure data, and bullet tech tests. But this Ruger gets your attention.
In the beginning I too was playing with some 600 gr bullets and 570s that you could get common. Later when CEB developed the 535 Raptors and 570 Solids I did some data with those with excellent results.
In 2012 I worked with Dan at CEB to make a 350 gr Lever Raptor in .510 caliber for a couple of 510 Alaskans I had on hand. Well, if you seat this bullet in a 510 Wells, add one of those Talon Tips from CEB, you have quite a serious bullet that can certainly handle some serious work. It is Buffalo Capable as well. In test work here it more than meets the requirements in depth of penetration to make it viable for buffalo. That said, if I were shooting buffalo I would go with the other CEB Combo, 475 Raptor/510 Solid, which I will mention next. None the less this 350 Raptor has what it takes to be extremely devastating on anything you turn it loose on. I did not do pressure work on the loads, but I was able to hit 3075 fps with RL 10X and 3007 fps with H-322 and zero signs of any pressure at all. Testing at 50 yards at 3007 fps it hit at 2850 fps with devastating impacts in medium.
Today I believe it also has a matching Solid at 400 gr.... this would be an extreme combination in the big 510 cartridge.
Also in 2012 my buddy Sam is a 500 Nitro fan. We already knew from past experience with these type bullets that you did not need the traditional weights that were normal in most big bore calibers. We already had a 535Raptor/570 Solid combo from CEB, but he designed a 475 Raptor/510 Solid combination that we tested in Australia 2012 with incredible results. We developed loads here in 500 Nitro running the 475/510 bullets at just over 2300 fps in his gun, at 39000 PSI with the 475 and 43000 PSI with the 510 Solid. This is pretty incredible for 500 Nitro. Time was very short, we did not have time to run terminal tests before leaving for Australia, but having a great deal of prior experience with these type bullets I had no doubts as to what they could do. And prove themselves they did, when big bulls were hit with the 475 Raptors at 2300 fps they just stood and quivered for a few seconds and dropped, the results were quite impressive. Most everything exited with the 475s unless it was a frontal shot or severe frontal angle. Only a few were recovered. None of the 510 Solids were recovered they all exited from front, from rear, from any angle. This combination has become standard now with anyone in the know. There have been many elephants taken now with the 510 Solids, extreme penetration, and in fact this week a friend of mine from Oklahoma is in Zimbabwe now with his 500 Nitro and 510 CEB Solids for elephant, he has taken several elephant now already with this bullet.
Since I have never considered taking the 510 Wells to the field, unfortunately I have not tested or done load data with the 475Raptor/510 Solid combination, but I believe a friend of mine in Texas is running the 475s at over 2500 fps in his 500 A Square as best I recall........
Really, the days of requiring heavy 600 gr bullets in this caliber are long gone...... When you can shoot from one end to the other on elephant with a 510, what do you need a 600 for?