Trigger engineering question.

[Larry (Omaha)]

Most of us all like a light pull trigger. A lighter trigger is usually what I strive for when I make a rifle. I am now working on a Harpers Ferry flintlock rifle. I intend to shoot it in musket matches (yes it has been OKed by NMLRA officials). NMLRA musket matches require a 3 lb minimum limit trigger pull. Here is why I am asking for help. The diagram shows geometry for trigger pull. My question: Should I go with middle one using 1/4", or move the pivot to maybe 5/16". My thought is if I go with the middle 1/4" without thinning the sear spring I would be in the ball park. I also am considering the fact that all locks trip with different energy levels on the sear to begin with. We are talking averages here. Suggestions would be appreciated.
Larry

 

[64Springer]

I ain't no rocket surgeon, but I'll take diagram two. Although diagram one would get the sear nose off the full cock notch faster.

Seems to me that lessoning the force by half, diagram 2, will mean the trigger pull will be twice as long.

Where is the sear spring going to be located? Sear bar? In the middle? Nearer to the sear screw? I would think sear spring location would have a greater impact on trigger pull than the sear/trigger relationship.

 

[user 34300]

The sear spring should be as close as possible to the pivot screw. I see a lot of them far back. This causes excessive friction and uneven pressure from the spring. I normally make new sear springs and fit them as close as possible to the pivot screw. Make all contact points a high polish. Consider making a new sear screw that fits the sear hole closely. Having the sear spring excessively strong also tends to have the sear nose impact the fly or half cock notch harder. This is tough on the lock. Do not reduce the full cock notch depth. Make sure to maintain the full cock angle to slightly cam the cock back. Be certain you are getting sear nose engagement fully across the sear notch. Check the with sharpie marker. Do break the wire edge on the sear nose and full cock notch. I mean just a couple of strokes on a hard Arkansas or #2000 grit diamond plate. If you don't the edges will crumble because the forces on the tiny wire edge become huge.

As far as pivot distance, #3 is your best mechanical advantage. The exact pivot distance I can not tell you. I see no reason a 3/8" will not give a good feeling pull. The trade off of a short distance is a long trigger pull. If you tune the lock properly you will not need to use a long pull. IF you do not tune the lock the long pull will feel bad anyway.