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Discussion Starter · #1 ·
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:



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
 

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Excellent Art! I like a guy who says he's gonna do something and then does it. I hope it all works out great. I will probably have to get another rifle to install this in when it's final because I don't want a match trigger in my defense rifle. Keep up the good work and I hope you make a few $$$.
 

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Discussion Starter · #3 ·
Zeus,

I don't want to stand in the way of you getting a new rifle, but these triggers will not be 'match' in any way that would disqualify them from a combat or defense rifle. Quite the opposite.

The key differences I hope to offer will include:

1. Higher grade steel, so the edges of the sear can get and hold a sharp edge, which will make the trigger feel more crisp when the hammer breaks.
2. Wider sear engagement surface which will reduce surface load versus stock parts, reducing wear.
3. Possibly eliminating some of the slack between the trigger and the sear, so you won't have that first bump in the trigger travel.
4. A high strength hammer spring, so you get faster and more positive ignition - also good for a combat rifle.
5. A PVD coating that will make the bearing surfaces both hard, and corrosion resistant, and low friction, so the trigger feel will be smooth and less gritty, even with no lube. Lube acts as glue, so dust and combustion products stick to it, and affectt he smoothness and wear on the trigger surfaces. A PVD will make it run like a dream when it is bone dry, reducing cleaning, and improving relaibility (not that there is a problem with reliability in the current design, but more is always better).
6. The only difference that will be 'match' is that I will likely also include reduced weight springs for the trigger and plunger, should you want to reduce the trigger pull. But if you don't want this, you'd just install the trigger using your original springs, and it would be sprung like a stock trigger.

Net, the trigger will perform as well and as robustly (or better) as any combat trigger, it will just feel a lot smoother and break a lot cleaner.

Be sure, I am designing this trigger for people like YOU, who own the 556 as a combat weapon. As far as I know, there is no match market for a 556, so if my trigger were too delicate for a combat rifle, I'd only ever sell about 3 of them. What I am after is to get the performance improvements that a match trigger offers, and build them into a combat trigger. Maybe I should call it a comb-match trigger.

The only aspect of my trigger that will not be combat is that it will only ever be semi-automatic, whereas the parts in SIG's original design could be used for both semi and select fire.

Art
 

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Very good to know. I would definately be interested in any high quality upgrades, not that I am unhappy with the current parts.
 

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Any trigger parts that you make I am sure they will be great. I would love to have as many alternative parts for the Sig and be able to replace parts if needed. This is all good. As many parts for the Sig you make, I will buy and even spares. Keep up the great work and let us know when your ready to sell. :wink:
 

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7art, great job on your trigger project, i think i might need one :wink: Just curious on your choice of steel,why 1018 CRS? IMHO I feel 8620H would be a better choice of steel.Just as an example, The M-14 receiver,bolt, hammer,trigger and sear are made from 8620 and 8620H, Its an ordnance grade steel and is a proven winner. Good luck with the project, i hope you get it into production soon.
 

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Discussion Starter · #7 ·
The steel I chose is A2, which is cold rolled, hardenable tool steel.

I confess, I do not know what 1018 CRS is, or how it differs.

8620 is a carburizing alloy, which means you develop a case hardening by packing it in a high carbon/nitrogen substance, and heating it, so the carbon migrates into the surface, producing a 'case hardening', The problem is that this high carbon layer is only a few thou deep.

Another approach is to disolve excess carbon in the molten steel while it is still liquid, so it mixes throughout the iron, then cool it quick enough that the carbon stays trapped interstitially in the iron matrix. When you heat treat this, the exess carbon (or other alloying agents) do not need to come from the surface, and remain close to the surface, but are already trapped throughout the body of the steel, so the entire part gets excess carbon.

I fully accept that I am an engineer trying to explain what a metallurgist should be discussing,so it is right as far as I know, but that don't mean it is right in the absolute ...

Art
 

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Discussion Starter · #8 ·
Update:

My EDM guy worked this weekend to get me Gen 2 parts in time that I can get finish machine, heat treat, and coating in time to take samples to the SHOT show in Las Vegas in 2 weeks. I hope to show a match grade trigger to SIG while I am there.

Gen 2 design changes are that the hammer is 3/16" thick, rather than 1/4". By going thinner, I can keep the same polar moment of inertia as the original SIG design (that was 1/4" thick with thin sections), or as my Gen 1 design which was 1/4" thick with skeletonizing holes. Net, I'm matching performance with less machining cost.

Also, the original SIG hamer was brazed/soldered to the hub, and appears to be slightly off-center. I have a machind hub with a shoulder which is pressed in place, and better registers the hammer in the lower receiver, so it is on-center every time.

I have also made some geometry changes to the hammer that were necessary to facilitate post EDM machining. Not sure if these will be necesary long term, but they make the part easier to manufacture now.

At present, G2 hammers still have a thin section at the hub, so the stock SIG hammer spring wil fit.

Question: is it cheaper to make a 3/16" thick hammer, and mill out pockets on 2 sides (G2 design), so the stock spring fits a 3mm thick central web, or is it better to just make a 3/16" thick hammer (G3), and make a new hammer spring that has a 3/16" bridge, to avoid the extra machining?

My experience is that custom springs are only a few dollars a piece, and custom springs also allow me to 'up' spring stiffness, to increase ignition energy and decrease lock time.

I think it is a no-brainer, it's just that the development cycle of getting a new spring adds to the total development time for the product.

Art
 

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Art, in your OP when you stated you were using cold rolled tool steel i assumed you meant 1018 cold rolled, my mistake. Like 8620 1018 must be carburized to harden. The reason i mentioned the use of 8620H is because you can case harden it for durability and still have a relatively ''soft" core for some "flexibilty" to avoid cracking. I use A-2 quite a bit at work to make dies and fixtures, its one of my favorite steels to use.
 

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Discussion Starter · #11 ·
The A2 will be hardened to around 55Rc. This is not as hard as it can get, but, as you point out, it preserves some ductility to avoid cracking.

Surface coating is still being investigated. Melonite QPQ coatings are a candidate, as these put a surface of something like 80Rc on the part. However, I want to look at CrN coating, as well as one or two others that additionally impart a low coefficient of friction.

Interstingly, all of this technology is used in the tool and die industry to increase the life of punch dies, which get way more load/abuse than a sear/hammer do, so I have high hopes the end product will be a winner.

Art
 

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7art,

I may be way off base here, but if you are going to be selling some gun parts, it would be nice to know your actual full name, business name, and maybe some contact info. I am new to this forum, so possibly you are so famous that you require no introduction, but for a complete newbie like myself, please help me out.

Tony Rumore
Tromix Corp
 

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Discussion Starter · #15 ·
My full name is Art Neergaard, I work for X-Treme Shooting Products in Cincinnati, Ohio. Our web site is:
http://www.x-tremeshooting.com

We specialize in match triggers for the AR, the Rem 700, and we make 30mm front sights for long-range shooting. Our claim to fame is that our triggers are all machined from cold rolled tool steel, and fully hardened - none of our triggers are cast/case hardened. We believe tool steel gives a stronger sear edge, so the sears will stay sharper, giving a cleaner break to the trigger. Our triggers are all EDM cut (the founder of the company is a tool & die maker who owned an EDM shop).

I also have my own business, making competition apertures for AR rifles, and other vision related products for shooters. My own web site is:
http://www.shootingsight.com

For my real job, I do R&D for Procter & Gamble, where I have worked for 25 years doing package, devices, and machine design. During this work, I spent 1 year living in Switzerland, working with SIG Packaging Systems to develop a new sealing system for their high speed flow wrapping equipment. This was in the mid 90's, before they sold off the arms division, so I have no experience working with the current SIG Arms.

At NRA convention last year, we met with the CEO of SIG, and then the 556 product manager. They were impressed with the quality of our AR triggers, and were wondering if we could re-apply our manufacturing techniques to improve the 556 trigger, so I undertook that project in my spare time. Now, 6ish months later, I am making my first prototypes for testing. I'll be showing these to SIG at the SHOT show next week.

In order to gage the interest in the market, I joined this forum about 6 months ago and have posted in threads pertaining to optics and triggers.

My background is that I am a mechanical engineer, and I also studied optics and high speed photography. I am a competitive highpower and long-range shooter . For high power, I shoot AR and M-1A at 200, 300, and 600 yards, all with metallic sights. I shoot in club natches, but have also shot three times at the National Matches at Camp Perry, in Ohio. In long range I shoot 800, 900, and 1,000 yards with a Remington 700, chambered in 6XC, using both metallic sights and a scope, though I am a newbie in this discipline.

I am in my late 40's, and got interested in applying optics to shooting when my near vision went bad, so I started studying the application of optical physics to apertures and corrective lenses for shooting needs. This led to an invention of a rectangular shaped aperture, which wil bias your depth of field, to improve focus onthe front sight and target, without giving up brightness due to an undersized aperture. Patent is pending (for 3 years now), but the latest communication from the patent office indicates it might grant in the next few months.

Art Neergaard
ShootingSight LLC
X-Treme Shooting Products LLC
 

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Sounds all good Art. I plan to buy some of your Sig triggers when you get them done. Now I know who I will be buying them from. Thank you.

Tony Rumore
Tromix.
 

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Art, if the price stays in the sub $200 range put me down for one! One question-how will this affect the relatively long take-up of the factory trigger?
 

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Discussion Starter · #19 ·
Tiger,

Not sure about if my system will solve the trigger take-up distance. Truth is that the trigger travels much further forward than it needs to, and I do have a solution I put in my lower, but I have not found a slick way to implement it that does not require stuff you don't want to do ....

like drilling holes in your rifle.

Bottom line, my first two generations of prototype parts are in, and give a pretty good match trigger. I still need one or two tweaks, but it is good enough that I fly to the SHOT show in vegas and have samples to show SIG.
Art
 

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hey 7art, when do you want me to stop by and pick one up for BETA testing ?!?!?!? :)

I work at an indoor range and can definitely get some time to beat it up for you. Just remember, I'm here to help. And since I know machining and stuff, I could give you intelligent feedback.
 
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