Trigger placement and angle

[Elnathan]

I don't think I've ever posted this yet, despite thinking about this for quite awhile now...

Standard practice for pinned single triggers these days is to place the pin about 1/4" to 3/8" in front of and at the same level as the sear bar. There is some disagreement over exactly how close the trigger should be pinned, but most folks would fall into somewhere into that range, I think.

What I am wondering about is altering the angle of the internal part of the trigger to bring the pad forward or backwards in relation to the lock, while maintaining the same distance between the pin and the sear. Here is a poorly drawn diagram that might or might not help explain what I mean:


In all three triggers the distance between the trigger pin (green) and the sear bar (red) is the same, and all look identical below the stock line (just pretend). Figure A is the way triggers are usually installed, I think, with the leading edge of the trigger bar straight up and down and the pin more or less directly above the finger will pull. Figure B is tilted backwards so that the finger is behind the pin, moving visible part of the trigger backwards in relation to the lock. Figure C is the opposite, with the leading edge of the trigger bar tilted backwards, moving the finger in front of the pin and the visible trigger forwards in relation to the lock.

I think that, assuming that the finger is the same distance to the pin when in use, all three arrangements should give the same weight of pull. In other words, the actual shape of the lever makes no difference as long as the distance between the fulcrum (the trigger pin here) and opposing forces (the finger and the sear) remain the same. There are some differences in the clearances needed to ensure that the trigger can move without banging into the bottom of the stock or trigger guard, but overall these triggers should function like triggers slanted forwards (like some originals) or backwards (like some made today).

The reason I was thinking about this was that many original rifles don't seem to have been built with the modern concern for a short distance between the sear and trigger pin and have the trigger installed fairly far forwards in the stock. One rifle I'm looking at in particular, if shaped like A inside, would give a distance of at least 3/4" between the sear bar and trigger pin. While I like the idea of pinning the trigger a bit further away than the 1/4" often recommended (My rifle with a 1/4" placement has an awfully mushy trigger), 3/4" seems like a bit much. OTOH, I'm planning on using a barrel with a smaller breech and a longer pull on my interpretation of this piece, and moving the trigger forwards in relation to the lock and thereby shortening the overall stock would help me keep the proportions closer to the original rifle.

I don't think I've seen this particular concept discussed here before, though maybe I just missed it.

[mtlonghunter]

I think you've forgotten one other position, where the trigger bar lifts the sear strait up which is the direction it has to go. All of the other pictures show it moving back and up which makes it slide up the trigger and makes more friction. Now I realize that we are not talking about rocket science here , but a smooth trigger  needs as little friction as possible. Just a thot.

[Elnathan]

Mtnlonghunter,

My quick sketch isn't all that precise. I was assuming that the pin was more or less on the same plane as the sear screw, which should give a minimum of friction between the sear arm and the trigger bar (having the pin directly behind the sear screw would of course have little to no movement between the two, but has less mechanical advantage that a pin close to the sear bar). In any case, while trigger placement in general is a worthy subject, I was hoping to discuss a particular variable.

Did you see the PM I sent you awhile back, BTW?

[mtlonghunter]

No I didn't?

[mtlonghunter]

This is an interesting topic. My general rule of thumb has always  been the closer to the sear the pivot point, the more mechanical advantage. However the longer the trigger pull, more creep. Further away, the less advantage and harder the pull, but less creep. I'm not sure the distance to the sear screw has any thing to do with it. It still takes a certain force to trip the sear and disengage the tumbler, based on mainspring tension and sear spring tension, polished contact points ,etc. Later.

[Eric Krewson]

I put mine level, 5/16" from the pin and have a low creep 3# trigger generally, the last one was 2 1/2#.

[Darkhorse]

I would tend  to think that a pin placement slightly farther away would give more mechanical advantage to the shooter. Sorta like trying to move a heavy object with a long pole, the farther out on the pole you pull the easier it is to move the object. Some real world tests with a donor gunstock should tell the tale. There should be room to drill several pin holes in a line of increasing distance from the sear in a single stock. Testing with a good trigger pull gage should give an answer.

[stubshaft]

The pin is the fulcrum.  Think of the trigger itself as the lever.

[RichG]

at the Oregon gun makers fair last April, Dave Rase had a lock fixture with adjustable trigger placement. I can't remember if it was up/down or front/back adjustments that showed massive creep. strange thing was that pull weight didn't change much. maybe Dave can weigh in.

[Elnathan]

No I didn't?

OK. I sent a new one.