Set trigger placement

[Tom A Hawk]

On the rifles I have made having double set triggers I have installed the trigger assembly according to the recommendations at a point slightly forward of the midpoint between the pivot pins. While the front trigger can be made to fire unset, it is not remotely of reasonable poundage. If you more experienced makers have any tricks up your apron to achieving a good unset trigger pull, please feel free to share. Thanks.

 

[Larry (Omaha)]

On the rifles I have made having double set triggers I have installed the trigger assembly according to the recommendations at a point slightly forward of the midpoint between the pivot pins. While the front trigger can be made to fire unset, it is not remotely of reasonable poundage. If you more experienced makers have any tricks up your apron to achieving a good unset trigger pull, please feel free to share. Thanks.

Unset trigger pull weight is in conjunction with the mechanical leverage between pivot point and sear bar. The closer the trigger pivot is to the sear, the less energy it takes and vice versa. If the trigger works OK set, I would lighten the sear spring a tad and that should help. Other members may chime in with more suggestions.
Good luck

 

[Phil Coffins]

I tune the sear and tumbler for a nice pull independent of the triggers. With a clean crisp break of the sear on the lock the trigger will be good either set or unset.

 

[Tom A Hawk]

I tune the sear and tumbler for a nice pull independent of the triggers. With a clean crisp break of the sear on the lock the trigger will be good either set or unset.

Phil - Can you expand on that a bit? My locks seem to break cleanly, but with the front trigger unset the pull is very hard.

 

[Phil Coffins]

I look at the lock completely independent of the gun, that is the angle of the engaging parts need to be such as the sear will hold the tumbler with out a spring and the depth of engagement is no more then the thickness of the sear. With the surfaces sharp and smooth the spring needs to move the sear into place not hold it. The set triggers as well need to move easily and have a crisp engagement, the adjusting screw only determines the amount of travel to trip. As you know the leverage of the trigger is set in relation to the length of the trigger and the bar of the trigger so if this is one to one a three pound sear pull will produce a three pound trigger pull. If the bar engages the sear at a different point then that percent changes to a more or less pull and the travel becomes longer or shorter. Still if the lock takes a lot to trip then it requires a lot of advantage on the trigger. I’m not much of a word smith but hope this makes some sense.

 

[Tom A Hawk]

Thank you. One would think the sear/tumbler engage on a $200 lock would be properly set.

 

[Larry (Omaha)]

Thank you. One would think the sear/tumbler engage on a $200 lock would be properly set.

Phil has some very good information. One you need to recognize is the sear engagement via the spring.
"the spring needs to move the sear into place not hold it." (Phil) Trigger pull weight is added by a stiff sear spring. Thin the sear spring, so the sear engages solid and no more.

 

[Col. Batguano]

You want your sear bar as far forward as possible that will give you 100% reliability when firing set. If there is extra depth to the tumbler shelf taking that off will help. Just be careful though because that can also compromise safety. If you can figure out how to add some weight to the set trigger blade (like lengthening it with additional metal added) that will add inertia to the strike force energy transfer. The further out from the pivot point you can place the additional mass, the greater the effect. Polish your pivot pin and blade hole to lessen drag. Lightening the sear spring as suggested above will be the biggest one though.

 

[Tom A Hawk]

Thanks all for your input. Now I'm wishing for a "Try" fixture that would hold the lock and trigger assembly in alignment so that the function can be evaluated in different trigger plate positions while out of the stock. Finding out the position is wrong after inletting would be unpleasant.

 

[SDSmlf]

Thanks all for your input. Now I'm wishing for a "Try" fixture that would hold the lock and trigger assembly in alignment so that the function can be evaluated in different trigger plate positions while out of the stock. Finding out the position is wrong after inletting would be unpleasant.

One way to check out geometry a bit would be with scale drawings or photographs. If your parts set is from the TOW you may be able to visualize what you want with the photographs from their catalog.