I watched 22plinkster, on YouTube, shoot some monster rounds for a 500 S&W. I think they were around 700 grains. He was having trouble with them tumbling since they were so big. Hopefully you won't have the same problem.
I load up semi-wadcutters for my 1911 and have good luck with them. I assume those are for your six shooter? That's a pretty heavy bullet and a quick research for load data says it's for bowling pin shooting and some special care is needed for reloading to prevent bulging. Looks interesting!
Here is a excerpt, no claim made to the accuracy of it, just for FYI
This bullet was designed specifically for bowling pin shoots. In these types of competitive events in which the objective is to clear a table of bowling pins; weight is more effective than velocity. This bullet is soft cast and is rated for 900 fps. The Thunderhead maximum meplat profile with the softer alloy promotes a better engagement with the hardwood pins (usually maple). The design features dual crimp grooves so that it can be loaded in .38 or .357 cases depending upon your application. Because the body of the bullet is so long it must be sized to .357 or .3575 maximum to insure it does not excessively bulge the brass and thus prevent its chambering. In .357 cases, 9.0 grains of Accurate Arms will get the job done. If using .38 cases try about 7.0 grains to start. DO NOT use +P .38 cases as these are usually thicker and can cause excessive bulging .... This type of shooting sport was pioneered by Richard Davis of Second Chance body armor. This event became a Who's Who of the shooting world and was a very elite event. Bowling pin shoots are not as popular as they once were but still show up from time to time.
Penn Bullets makes em too and has some load data published on their site. I have aa9 in my powder stash, might try that first. Really just had them sent to be a conversation piece.