You won't need the powder stop for loading rifle. It is used when loading pistol using the powder through expander to expand and charge the case in the same step.
It's not that Varget isn't a good powder. It is. It just doesn't play nice with the LnL powder measure.
I really hope you didn't get that Varget. It is an extruded "stick" powder and it meters like gravel through the LnL AP powder measure. At least it does at 223 size charges. I never tried it with 308 size charges, but wouldn't expect it to be much better. It literally crunched every time I...