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Just wanted to update everyone who has been following my posts about a match trigger for the 556.
I got my first batch of prototypes from the EDM shop over the holiday, and did the final machining. They go out for heat treat tomorrow, and then a PVD surface coating sometime next week. Here are the pics:
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What you see are first the collection of parts, made from cold rolled tool steel, and EDM cut. The steel selection is so that I can get full depth hardening, which will allow the parts to get and hold sharp sear edges, giving the most 'crisp' hammer release possible. I made 8 sets to start with so I could experiment with some different PVD coatings, different design ideas, etc.
The middle picture shows a single set, close up. The original SIG hammer is a cast part, and they cast it thin in the middle to save weight, and reduce lock time. Since I am making these out of plate steel, I do not want thin sections. As a starting point, I made my parts as wide as SIG's design, and used the SIG profiles. To avoid having to machine thin sections, I drilled skeletonizing holes. Hole size and placement was calcualted so the finished part has the same polar moment as the original SIG part, so it will deliver the same lock time, and the same ignition energy. My final production design will be slightly narrower than the original SIG hammer, and will have a few profle modifications, so I can match the original polar moment without having to drill holes.
I did have to machine a thin section around the hub, so the stock hammer spring will fit. Long term, I'll get a custom hammer spring made that will eliminate these cutouts. I might even 'up' the spring energy slightly, to gain a few fractions of a millisecond in lock time. Current design is pretty fast at 4.5 milliseconds - a spring and tuned hammer might get into the 4.0ms range.
On the trigger sear, the big change is that I made it 2x as wide as the SIG sear, eliminating the plastic spacer, and doubling the width of the engagement surface against the hammer. This will reduce the PSI on the edges of the sear, and will permit a much sharper edge to be held, for an exceptionally crisp break. You might also notice I added a threaded hole in the little "finger" on the sear. The length of this finger controls sear engagement when the hammer is cocked. This hole was an attempt to make an adjustable 1st stage sear engagement (that's also why there is a discoloration on that finger tip, where I used a grinder to adjust sear engagement). Long term, this will go away.
You will notice that the hub has a bigger diameter on one side than the other. That's because it was designed as a press-in part, with a shoulder, so hammer centering in the frame will be dead on. SIG's design uses braze or silver solder to attach the hammer to the hub.
No word on pricing yet. The parts fabrication is tracking very closely with what I had predicted, though coating cost is unknown. I'm still optimistic these will sell in the $ 100 - $ 150 range.
More updates as events warrant.
Art
I got my first batch of prototypes from the EDM shop over the holiday, and did the final machining. They go out for heat treat tomorrow, and then a PVD surface coating sometime next week. Here are the pics:
What you see are first the collection of parts, made from cold rolled tool steel, and EDM cut. The steel selection is so that I can get full depth hardening, which will allow the parts to get and hold sharp sear edges, giving the most 'crisp' hammer release possible. I made 8 sets to start with so I could experiment with some different PVD coatings, different design ideas, etc.
The middle picture shows a single set, close up. The original SIG hammer is a cast part, and they cast it thin in the middle to save weight, and reduce lock time. Since I am making these out of plate steel, I do not want thin sections. As a starting point, I made my parts as wide as SIG's design, and used the SIG profiles. To avoid having to machine thin sections, I drilled skeletonizing holes. Hole size and placement was calcualted so the finished part has the same polar moment as the original SIG part, so it will deliver the same lock time, and the same ignition energy. My final production design will be slightly narrower than the original SIG hammer, and will have a few profle modifications, so I can match the original polar moment without having to drill holes.
I did have to machine a thin section around the hub, so the stock hammer spring will fit. Long term, I'll get a custom hammer spring made that will eliminate these cutouts. I might even 'up' the spring energy slightly, to gain a few fractions of a millisecond in lock time. Current design is pretty fast at 4.5 milliseconds - a spring and tuned hammer might get into the 4.0ms range.
On the trigger sear, the big change is that I made it 2x as wide as the SIG sear, eliminating the plastic spacer, and doubling the width of the engagement surface against the hammer. This will reduce the PSI on the edges of the sear, and will permit a much sharper edge to be held, for an exceptionally crisp break. You might also notice I added a threaded hole in the little "finger" on the sear. The length of this finger controls sear engagement when the hammer is cocked. This hole was an attempt to make an adjustable 1st stage sear engagement (that's also why there is a discoloration on that finger tip, where I used a grinder to adjust sear engagement). Long term, this will go away.
You will notice that the hub has a bigger diameter on one side than the other. That's because it was designed as a press-in part, with a shoulder, so hammer centering in the frame will be dead on. SIG's design uses braze or silver solder to attach the hammer to the hub.
No word on pricing yet. The parts fabrication is tracking very closely with what I had predicted, though coating cost is unknown. I'm still optimistic these will sell in the $ 100 - $ 150 range.
More updates as events warrant.
Art
