Trigger pivot pin question

[Bob Gerard]

What would be the optimum distance from the trigger pivot pin to the sear bar (on a Fowler or rifle)?

[TDM]

The longer the length the higher the trigger pull. 3/4” to an 1”. I’ve really never measured.

[Hungry Horse]

 Bob, I really don’t know what the higher position of the trigger pin relationship measurements are optimum, on a simple trigger. But, I did experiment on my sons miniature tradegun I built for him years ago. The first time around The trigger was pinned too high, and that trigger had almost no resistance at all. The travel was extreme, and the whole thing was exasperated by the long tradegun trigger. Luckily I was able to bore a new pivot pin hole in the trigger, and stock. I think that little gun ended up being pinned about 3/8 of an inch above the contact level sear bar.

Hungry Horse

[smylee grouch]

I have had good luck with the pin almost +\- the same night as sear pin and blade contact at the sear  about 3\8 inch behind pin.

[TDM]

Bob, I sketched out a diagram that should explain it better.

[J.D.]

What would be the optimum distance from the trigger pivot pin to the sear bar (on a Fowler or rifle)?

You might get an idea of the correct location of the trigger pivot pin hole by viewing one of Jim Kubler's instructional video on assembling one of his kits. The video is #3 Trigger and underlugs, if I remember correctly.

[bluenoser]

I would certainly defer to anything Jim has to say on the subject.
I try to get the height of trigger pivot point as close to the sear arm as possible to minimize creep and keep it 1/4" to maybe 3/8" forward of the contact point for a light pull.  That doesn't seem to result in an overly long trigger travel.

[Hungry Horse]

 The higher the pivot pin is, the more mechanical advantage, and the lighter the trigger pull. If the illustration was correct almost all cheap kit guns would have a great trigger. It is correct that getting the pivot pin, and the sear bar contact closer together helps.

Hungry Horse

[J. Talbert]

I would suggest that the distance from pivot point to sear is a trade off.  The shorter the distance the greater the mechanical advantage so therefore the lighter the pull, but at the same time the greater the amount of creep, as the movement of the bottom of the trigger translates to less movement of the trigger bar at the point of contact with the sear.

Jeff

[rich pierce]

Agree 100% with the posts on pivot placement impacting pull weight and creep.

Additional factors only for experienced lock tuners:
It can happen that the sear nose and/or full cock notch are rough. This impacts how the trigger feels.

Rarely, a full cock notch can be cut so that the working edge is not radial. That is, not on a straight line to the center of the tumbler axle. If too acute, lifting the sear nose actually rotates the tumbler and cock rearward and fights the mainspring. If too open an angle, the sear can slip off the full cock notch. Very unsafe.

A deep full cock notch is going to require more trigger travel, but be more safe.

The sear spring bearing surface polish and strength can impact trigger pull and smoothness.

When seeking a lighter trigger pull on a simple trigger, 3 pounds is good.

[smylee grouch]

That's a good point about the sear spring strength Rich. Another sear spring point is if the tip of the spring is back further on the top of the sear. That would give the spring more leverage to hold the spring in the full cock notch I'm thinking.

[Daryl]

3 pounds was the trigger weight of match rifles in the competitions I shot back in the 70's, for our "Match Rifles".
In around 1978 or so, this weight was reduced to 2 kilos, ie: 2.2pounds. The cocked rifle had to pick up a 1 kilo weight.
With triggers adjusted very closely, they'd put a piece of paper under the butt, with tension on it while the rifle's owner
picked the rifle up. If the tension-ed paper was able to be removed from under the butt, that trigger passed. 1 kilo felt
like a hair trigger compared to 3 pounds.
I still like a crisp 3 pound trigger,m without any creep.
I just checked my 14 bore's trigger and it's 4.16 pounds with barely a tiny bit of sponginess. It's not difficult to shoot reasonably well.

[Bob Gerard]

Thanks everyone! I will try to get the trigger pivot pin 1/4" to 3/8" from contact point on the sear bar and keep the pin at or just above the sear bar as well.

[Jim Kibler]

I think the tendency today is to place the pivot much closer to the sear arm as compared to original work.  The consequences or trade-offs are mentioned above.  With a good lock you can put the pivot 1/2"-5/8" from the sear arm and still get a good pull.  The advantage of this is much less creep or travel.  The best of both worlds...

[Bob Gerard]

I placed the pin a bit over 1/4” from the sear bar and the pull seems maybe 2# with like no creep. Really happy with it.

[Jim Kibler]

If it is just over 1/4" and requires a "small" amount of travel until the sear releases, the tumbler notch must be incredibly shallow or at a potentially unstable angle.

Jim

[Bob Gerard]

Well, it won't trip if you sneeze or anything 

[rich pierce]

Looks good!