That tool will be invaluable. Find a fired case from your rifle. Gauge your bump off of that. Not new brass. Bump it .001-.002" from fireformed length and you should be golden.

Also, your press, is it the Breech lock challenger? I use one. What dies are you using? Lee dies have the crappy o-ring under the nut. If you're using them, buy some locking split rings to replace them. Huge difference. I use Hornady rings on my Lee dies.