It is possible but not absolutely necessary and actually could be considered somewhat wasteful under some circumstances. I've often used a coil spring hammer with a flat spring lever and no flat spring, simply by timing the action properly so that the FP retraction action has all its lost motion removed. Simple and effective and relatively foolproof; very important in my case (G). Since this is SOP anyway on all the wall actions I rebuild, practically all my rifles could utilize only the coil mainspring if necessary, without suffering any lever droop.
Many single shot smiths don't seem to be aware of this action-timing procedure or else don't think it important, but I do. A properly-timed action is one of the very best preventives for broken firing pins, often a recurring problem with some walls. In the past I've addressed part of this action-timing procedure in a couple of articles in the ASSRA Journal, but I didn't expand them to specifically cover the use of a coil spring hammer with a leaf spring lever. It's probably worth another article.
Regards, Joe
