Usings a 7mm Rem Mag body die

Hi guys.

My system is Lee Collet dies and bumping with a Redding body die as required. Produced fantastic ammo easily/cheaply in my 7mm08.

I am struggling to get that precise bump with the Rem Mag and I suspect it is because the die sizes off the rim?
Norma brass.
I am have only had one crack at it but couldn't achieve consistent results.

I'm tempted to send the Die to a machine shop and extend the step for the rim a mill or so that the rim is still sized but the case length is not sized of the rim...if you get my drift.

Any thoughts?

I cant figure out how to edit this post but I should have said "belt" not "rim".