What is the difference between Stevens 44 and a 44.5?

Answer 1

The Stevens 44 action came first. It is a rolling-block type single shot and has four screws through the side of the action. The 44.5 action was first put on the market around 1903 and was developed for use with smokeless powder. It is a true falling block action and much stronger than the 44. It has higher side walls supporting the breach block. Ned Roberts, who developed the 257 Roberts cartridge used the 44.5 action for his experimental work sometimes with loads developing 50,000 psi chamber pressure. The breach block on the 44.5 has a "rocking" motion when opened or closed. This will press the cartridge into the chamber when the action is closed.

By about 1913 the market in America for single shot rifles was over and Stevens dropped it from their catalogs.

A modern version of the Stevens 44.5 is currently made by CPA Rifles. Their website shows several types of rifles made with this action.