Can somebody help.Just purchased S&W 44-40 Frontier DA.I think there is something missing inside.When pulling the trigger cylinder rotates,but hammer does not pull back.When cocking the hammer then pulling the trigger,the cylinder rotates and i am able to fire the gun.Are there any gunsmiths who can fix this

First, there is a very good chance you gun is just gunked up. Remove the grips, and place the gun in a container like a oil change pan. Cover it in solvent from an auto parts store and let it set for a day or so. Then, spray it with carb or brake cleaner, use the little tube that comes with the spray can and blast into every opening in frame. By trigger, by hammer, etc and work the action as you do. Then let dry then spray in a bit of quality gun lube.

I used to just say do the spray, but I tried that with a hard trigger on a rifle my brother had and got no where. I tore it down and found some old oil that had solidified and the card cleaner had not touched it. Was like stiff plastic. I am sure a soak in some solvent would have softened it up over time so that the spray would have removed it.

You could just try the spray and it it doesn't work try the soak and respray.

There is a possibility that the dbl action sear or its spring are defective. But, unless you are familiar with taking one apart or real mechanical, try the solvent first.

Thank you for helping.Just got a shematic for this model and looks like the front sear is missing and hand spring is replacement coil spring.Does anybody have a sear and hand spring for this.
Also,read somewhere this model is made like the smaller 38,will part from 38 fits this model