Most of the kit guns and factory guns have pretty rough trigger pulls and or unsafe trigger pulls. Mostly this is due to cheaping out on the build process. The following is a copy of the drawings made for me years ago by The fellows at Green River Rifle works and from correspondence with Bill Large and V M Starr.
As shown in the drawing above The sear itself moves in an arc and the standard factory trigger moves in a smaller arc that rubs against the sear as you pull the trigger. Help for this situation will be to polish both contacting surfaces as smooth as you can et them. I buff with Tripoli. The other problem is that the trigger is pivoted below the point of contact with the sear so you loose mechanical advantage.
Look at the reproduction musket trigger assembly and you will notice that the sear contact point is way above the pivot point this in effect doubles the effort you need to move the sear. The original guard has the pivot point even with the sear. Much better is the trigger from an 1842 Johnson Pistol. When installed like the drawing the sear contact is BELOW the pivot point giving you mechanical advantage. With the proper angle of pressure on the sear and the placement of the pivot point the trigger actually decreases the effort needed to pull off the sear. In addition the curve from the pivot point down to the sear causes the force of the pull to be more inline with the arc of the sear.
In this case the lock takes 6 pounds of pull against the sear to release but due to mechanical advantage the trigger pulls just 3 pounds crisp and safe to fire the gun.
A properly set up single trigger can deliver a safe reliable 2# trigger pull. The higher you pivot the trigger within reason and design of the gun the less effort to fire the gun.