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391 release triggers-how they work

Discussion in 'Uncategorized Threads' started by Dickgshot, Oct 30, 2008.

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  1. Dickgshot

    Dickgshot Well-Known Member

    Joined:
    Jan 29, 1998
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    3,676
    A factor in the popularity of the 300 Series Beretta semi-automatic shotguns is how easily and inexpensively the trigger can be converted to a “release trigger." I fooled with a couple of them in the past week, and thought I would write about what I learned that some people might find interesting. This is a synopsis of what I wrote for another forum.


    To understand the release conversion, you first need to know how a 391 (or 390, 303, etc.) trigger works. On the trigger are two spring loaded sears. One is on the front top of the trigger with a hook that faces the rear. The other is a separate sear held by a bushing that goes through the trigger pivot hole. It has a hook facing forward.

    If you now look at the hammer, you will see two notches, one on each side. One engages the hook on the front sear, and the other the hook on the back sear. Since the trigger pivots, one sear engages the hammer when the trigger is pulled back, the other when the trigger is released forward.

    When you pull the bolt handle back, the bolt pushes the hammer back to a cocked position. Before it reaches its fully cocked position, the hammer pushes aside the spring-loaded forward sear, which lets the hammer move past it, then snaps back to lock it in place.

    Pulling the trigger moves both sears forward, disengaging the front sear from the hammer, which, under pressure from the hammer spring snaps forward to strike the firing pin and fire the gun.

    After the gun is fired, the hammer moves back in a fraction of a second, well before the shooter has released the trigger. With the trigger pulled back, the forward sear is still in its forward position and cannot catch the hammer. To the rescue comes the back sear, which has moved to its fully forward position and catches the other side of hammer just as the forward sear did.

    Of course, preparing for the next shot, the shooter has to first release the trigger. As he does, the rear sear moving back disengages the hammer, which travels only a fraction of an inch before it is captured by front sear, which moved back at the same time, and remains cocked. . So far so good. Now when the shooter pulls the trigger, the front sear releases the hammer as it did before – but wait! What about the rear sear? It also moved forward, so why didn't it grab the hammer? The rear hook is slightly lower than the one in front, so when the hammer was released, it was already past it.


    Now, it is easy to understand the release conversion: If you replace the rear sear with a specially designed release hook, it will allow the trigger to work differently – but safely - as a “release” trigger. This release hook is longer and set at a slightly different angle than the original sear, but is otherwise very similar. (also, the spring and plunger are replaced with a small solid rod to hold the release hook solidly in the trigger)

    When the trigger is pulled and the hammer released, it travels only about 1/8 of an inch before the release hook, which has moved forward, catches the notch in the hammer, stopping it and holding it in a cocked position. This is called “setting the trigger.” As long as the trigger is held back, the hammer will not drop.

    When the shooter wants to fire, he relaxes the pressure on the trigger, allowing the trigger to move forward, disengaging the release hook from the hammer which snaps forward firing the gun. The release hook is much longer than the pull sear, so when the hammer is released it is well past the hook on the front sear -the reverse of what happened with the pull sear.

    Since the trigger was released, it is again the front sear not the back sear that is in position to capture the rebounding hammer and lock it in place. For the second shot, the trigger is again pulled to set the hammer, then released to fire the gun. With just a little practice, it is not difficult to set and release the trigger for both the first and second shot of doubles.
     
  2. Dickgshot

    Dickgshot Well-Known Member

    Joined:
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