Need a lesson in Trigger Pull-101

[Steeltrap]

The last few builds I did I located the trigger pivot point no further away than the 1/4" recommended by "The Gunsmith of Grenville" publication.

Now, when my lock is held in my hand, I can trip the sear bar and I don't really notice any "sponginess" in the sear bar.

However, when the lock is placed in the rifle, I have "trigger travel" with a spongy feel until the sear trips and the hammer falls. On my most recent build the trigger pull is a very light 2.5-lbs. (I did tune the lock and polish all contact points)

I guess I'm not understanding why I have the spongy section of the trigger pull. Any input would be appreciated.

[bluenoser]

I also try to place the pivot point approximately 1/4" to 3/8" away from the contact point and accept the increased trigger travel as a trade-off.  It is simple geometry.  The closer the pivot point is to the contact point, the further the trigger has to travel to reach the break point.  There are possibilities for reducing the distance the sear needs to travel, but you need to understand the geometry and be aware of the potential effect on safety.  One possibility is reduction of an overly-deep full cock notch by shimming.

[t.caster]

I also tried 1/4" distance once on a rifle, per "Gunsmith of Grenville" and it was very light, but I didn't like the trigger travel before let-off.

I researched back to my first gun building book "RECREATING THE AMERICAN LONGRIFLE" by Wm. Buchele & G. Shumway, copyrighted 1970. They state the optimal distance from sear to pivot point between 5/16" to 3/8" and as high as possible above the trigger plate (to paraphrase the authors).
Modify message. They also said 1/4" was too short and caused more trigger creep.

[bluenoser]

Tom has made a couple of good points and I likely misspoke.  As I think if it, locating the pivot point within 1/4" of the point of contact would be challenging in many builds due to close proximity to the sear hole..  Forgot to mention the desirability of a high pivot point.

[Steeltrap]

So what I’m reading here and on another thread, the Grenville recommendation of 1/4” is not the preferred setup. Moving the pivot point to twice that distance, then tuning the lock to obtain a lower pull is a better way to go.

[J Shingler]

First it to pin to the wood. Those trigger plates with the trigger attached are generally too low. My triggers are pinned above the sear. The trigger is angled back down to fit under the sear bar. I likte a distance of 3/8" to give a very nice pull.

[Scota4570]

Your trigger is a lever.  IF one end of the lever is 1/4" from the fulcrum and the other is 2", you have an 8:1 mechanical advantage.  You also have an 8X longer travel of the trigger finger.  That makes the trigger feel light but also spongy. 

IMHO a well made lock does not need this treatment.  IF the screws fit the holes, and the tumbler is a good fit in the plate you will not have slop that needs to be taken up to fire the lock. Slop causes a spongy feel. 

Also the angles of the sear nose and tumbler notch need to be correct.  The sear notch should not be excessively deep.   But a very shallow engagement or beveled sear nose is a mistake.  IF the hammer is moving back too much when you pull the trigger, you are fighting unfortunate geometry.  The sear spring should be bearing as close to the sear pivot as possible.  Finally, everything should be polished to remove all tool marks that cause drag.  I go to a 2000 grit diamond lap then jewelers rouge on leather. 

[Dphariss]

If the lock is correct the distance to the trigger pivot is not an issue. And creepy triggers suck.

[Dphariss]

I might add that publishing a book is no sign the writer is correct or is even proficient in everything he writes about.

[Steeltrap]

I might add that publishing a book is no sign the writer is correct or is even proficient in everything he writes about.

I'm finding that out.

[Darkhorse]

Some things he's right about. Some things he's not. Before cutting wood or metal it's a good idea to post a question in this forum.