Wednesday, November 17, 2021

Speculative idea about rifle accuracy


The function of the trigger, as a mechanism, is determined by the distance between the pivot-pin and all of the locations where forces are applied or resisted

Sometimes, less is more.

Schlage Locks

All of the locks and door knobs in my house are made by Schlage Lock.

In one case I had the opportunity to shorten up the bolt of a dead-bolt lock for some reason that I cannot remember.

I was surprised to see a free-floating, hardened steel rod inside the bolt.

After a tiny bit of thought, it occurred to me that a free-floating pin is free to spin. That rod is almost impossible to cut with a Sawz-all or even a grinder. Both tools require that the surface being cut be stationary so there can be relative velocity between the teeth or the abrasive.

If the rod is unconstrained so it can spin freely, it will happily spin within the bolt-proper until the cows come home. 

Sure, an enterprising thief can fill the space in the dead-bolt with expanding foam or cut from one direction and then jam in a screwdriver blade to trap the rod...and attack from the other direction. Alternatively, the thief can attack the bolt on-the-bias with his abrasive wheel. All of those strategies take longer and increase the exposure of the thief to being noticed.

The key point is that the lock was "hardened" by removing structure (or a constraint), not by adding more.

Triggers and marksmanship

One tip that I picked up at The Art of the Rifle blog was to move my trigger hand grip forward so the only contact points between my hand and the pistol grip are the ham-of-my-thumb and the pads of my fingers. The shooter is essentially pinching the pistol grip between those two parts of his hand. It made a big difference in my field accuracy.

"Gripping" the pistol grip imparts a torque on the stock and the stock squirms at the break of the trigger. The "pinch grip" described above does not impart a torque.

Combine those two thoughts...

What if the pivot-pin of the trigger were replaced with a ball-joint or a Heim joint?

The current setup allows the shooter to create a torsional equilibrium between his trigger finger and the rest of his "grip". When the trigger breaks, then the equilibrium is broken and the stock can shift or jump ever-so-slightly as the lock trips and the firing pin detonates the primer.

And then there is the temptation to jerk the trigger. 

What if it was impossible to put side-load on the trigger because it would simple track to the side-of-center? That is, the trigger would not resist forces in that direction. It would be up to the shooter to train his trigger finger to moved aft direction with no side-forces.

As Jeff Cooper once noted, we do not rise to the occasion when we are under stress. Rather, we regress to the level of training that we have mastered. So this gimballed or ball-joint pivot trigger is likely to have more value as a training tool because we certainly don't want the trigger to drift outside of the trigger guard where twigs could snag on it. 

But I find it an interesting mental exercise. Maybe those "accuritizing kits" that shim the trigger to remove side-slop are exactly the wrong way to go. The trigger might feel better and more precise, but perhaps the results (especially when the adrenalin is flowing) might be to have the trigger loosy-goosy in the "Y" direction so jerking the trigger will not hose your aim.


  1. That should not be happening. The rifle should NOT jump when you press the trigger. If it does, either you don't have your finger on the trigger correctly, or the trigger has issues.

    1. I am frustrated with my self because of my inability to communicate the pictures in my head using common English.

      I agree that it is related to the correct use of the trigger BUT the rifle only needs to yaw or pitch 1/15th of a degree for the point-of-impact to shift 4" at 100 yards. That degree of shift is likely to be more than is acceptable. Even having the rifle roll will change the point-of-impact some.

      The picture in my head was to desensitize the rifle, even if just as a blue-sky trial, to one more source of noise from the shooter.

      I practice shooting. Not as much as I should. But when I am looking at a nice deer and I have seconds to shoot it, I cannot guarantee that I use the best practices I have "Mastered". A very, very nice buck reduces me to caveman-with-club, amygdala-dominated brain.

    2. I think a traditional solution to this is using a set trigger. Get everything ready, operate set trigger slowly to keep sites lined up, then firing trigger requires ~0 travel so it can't perturb the rifle.

      I know, for me, torque on the trigger is the issue under stress. I'm wondering if I went from a curved 1911 style to a flat trigger and then the flat trigger was capable of freely rotating it would prevent my finger torquing the rifle as I pulled. Essentially analogous to a gimbal mounted trigger, the useful input is "user operation of triggering device", not "user is operating triggering device in a straight line" so designing a system that is agnostic to rotational or lateral force on trigger is an improvement in function.

    3. The thing to do then, is to put the unloaded rifle in a lead sled (never with more than 25lbs of weight. That way, YOU are basically hard mounting the rifle. Using a snap cap, then press the trigger with various configurations of finger until you find that 'sweet spot' for that rifle. Re rotation, that shouldn't be happening either, if you've got the rifle tight in your shoulder. There shouldn't be any way for just your hand to roll the rifle that much. As far as repeatability, my gunsmith in NOVA was a bench shooter also. I've seen his target with ten rounds in a .2 hole shooting .308 rounds, so I know it is doable. With my sniper rifles, I can cloverleaf five rounds and cover them with a quarter on a good day.

  2. I run a .30-06 and it jumps every time I press the bang button. But if you ride the same bronco enough you get to the point you can ride him where you want. Just gotta learn the jumps.
    Kind of like them kids learning levels in a video game.
    But sometimes slop is your friend. To much rigidity is bad for a system. Gotta have some slip to accommodate the humans.

  3. ERJ
    Take a look at Trigger Tech triggers.
    Pricy but the only real major improvement in trigger design over the last 20 years

  4. Dry fire. A lot. It feels silly and pointless, but it isn't. And then more because to be human is to be lazy and impatient. Until your sight picture doesn't move, and proper trigger control is muscle memory.

  5. While firing, have a friend video your hands up close from all directions. Then watch the vids in slow motion. You'll be surprised what you see.


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