Deceptive? If we are talking about using 35 Remington cases when forming 6.5mm50 cases I would be concerned with the .010” difference in case head diameter.
Then there is the Model 99, the bore diameter is .311”, not 6.5mm (6.5mm50 fits the Model 38), if we are talking about a model 99 we should be talking about forming 7.7mm58 from 30/06.
I use a 308 Winchester form/trim die to form 7.7 cases. Using the 308 W forming/trim die is deceptively simple........for me, reloaders believe it is too short to form long cases, goes back to that old saying, “it is one thing to know how to hammer, it is another matter when knowing where to hammer”.
“other stuff involved?” Yes, I am not the fan of repeating what I have heard on the Internet, There is 21” of brass to trim when forming 100 7.7mm57 cases from 30/06, I use the man tool, the hack saw, when used with a forming tool trimming is simple and almost effortless.