Bill Geissele really thought of everything, and from what I’ve been told, what he didn’t think of the AMU suggested and he listened!
In short, I would describe it as having the adjustability of a Jewell, with the simplicity of a KAC.
The design is like the KAC, in it uses the trigger pin to hold the disconnector in place, so there are no extra pins to worry about.
The neat part is, there is not much that can go wrong will those pieces, as there is no place for them to go.
The disconnector is held in place by the trigger pin, and is incased in the raised walls of the trigger body. The disconnector spring, not only fits into a notch in the disconnector, but is also held in place by a follower. The 2nd stage weight screw, touches the follower, not the spring. So if that screw happened to come out, it wouldn’t matter, its not what’s holding the spring in place.
The sear engagement screw, is accessed through a cover with a hole to make sure it cannot come out.
• Lock time: About 50% faster
• Adjustability: A perfect trigger release is assured with all receivers and tolerances
• Quality Manufacture: Wire EDM cut
sear surfaces are smooth and precise
Lock time has been decreased with a lightened hammer that has a unique “IBeam” profile that decreases hammer mass while retaining strength. A standard hammer has a lock time of about15ms. In comparison, lock time with this trigger has been calculated at 8ms. This is an improvement of almost 50%. The shorter lock time can actually be felt by the shooter.
The hammer has also been designed to incorporate its “center of percussion” as near as possible to the firing pin longitudinal axis. When impact occurs on or near a rotating object’s center of percussion the reaction at the pivot point is minimized. This concept is best illustrated by a baseball being struck by the “sweet spot” of a baseball bat where the strike produces very little reaction into the batter’s hands. Incorporating a sweet spot into a rifle hammer will decrease the tendency of the hammer strike to disturb the rifle before the projectile has exited the barrel. It will also contribute in decreasing undesirable barrel vibrations induced in the barrel due to non-colinear firing pin impact. Mr. Harold Vaughn, in his “Rifle Accuracy Facts” has found that firing pin impact has a large influence in inducing barrel vibrations that are detrimental to accuracy.
Dry-firing the standard hammer will produce a sharp “thunk” that can be felt in the hands and seen by sight movement at hammer impact. When dry-firing, the hammer strike will be more like a smooth “schick” (for lack of better descriptive vocabulary) and sight movement from the hammer fall will be decreased or almost eliminated.
Sear engagement and 2nd stage weight are two separate adjustments on this trigger. No trade offs will have to be made between a light 2nd stage pull weight and a sharp 2nd stage break. With a separate sear adjustment, machining tolerances of the receiver are minimized and each trigger can be tuned for a perfect, crisp let off.
There is an overtravel adjustment screw that can be adjusted for shooters who want very little trigger movement after the 2nd stage break. Conversely, the geometry of the trigger has been designed to allow for maximum overtravel for shooters who want to ensure the projectile has exited the barrel before the trigger comes to a hard stop. Shooters that compete in National Infantry Trophy Team matches (600yds of rapid fire) might find the overtravel adjustment of most benefit since minimal overtravel will decrease trigger reset time and allow the trigger cycle time to be minimized.
Along with the above key points my hammer is designed to use the standard hammer spring rather than a modified or non-standard spring with decreased spring force. AR15’s with a lighter than standard hammer spring will have increased lock time and may have the possibility of an inadequate primer strike. Inadequate primer strike is of particular importance with the AR10.
This trigger was chosen by the USAMU for proof of concept on the new XM110 Semi-Auto Sniper System which uses the SR25/AR10 platform as its basis.
As a side note, during testing an AMU XM110 equipped with my trigger has produced 2-1/4” 5 round groups at 300 yards.
Many shooters, especially those with large hands, complain about crowding of their trigger finger on the standard trigger. To help remedy this the trigger surface was moved about 1/8” forward and modified the trigger curve
to allow a more relaxed position of the trigger finger. The 3/8” profile radius of the standard trigger has been retained which allows a smoother trigger pull when placing the first knuckle pivot on the trigger as some shooters prefer.
Unlike other 2-stage triggers, the separate disconnector on my trigger allows the trigger to be taken apart and cleaned in case of dirt ingress.
The price is a $279.00 and can be ordered HERE