For the .577 2 3/4, I would get some Horneber brass from www.huntingtons.com (or special order if necessary). More than half of the Bertram 600 NE brass I had would not even fit into my chamber. I had the same problem with about 20% of my 500 NE cases. The 600 NE were basically garbage, but I was able to file down the rims of the 500 NE to make them fit. But Horneber 600 NE worked every time. And Bell 500 NE was perfect.

Add to that the fact that Bertram is the most expensive brass out there, and I see no reason to mess with it.