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You have the first gen KAC trigger, much like as described here: www.quarterbore.com/kac/kac2stage.html I have a first gen and the model with two set screws. If you need a new hammer spring there are various makes you can get as there's probably nothing special about the KAC one. |
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so a 2-stage trigger basically has a disconnector and sear connected to the trigger and the front edge of the trigger just under the hammer pin no longer holds the hammer in place, correct? I'm talking about the sharp chiseled edge that is always polished in DIY trigger job threads- that portion doesn't engage the hammer in a two stage trigger? the two stage trigger's hammer can therefore do without the engagement area underneath like on the KAC. The RRA/LMT you show still has that notch on the underside of the hammer- it's not engaged by the trigger at all, or is it part of the first stage? |
It's been a while since I played with my dad's RRA 2-stage, but I'm pretty sure that notch doesn't do anything, and I don't know why they keep it there. The first stage and second stage are really all the same stage as far as sear engagement goes. The first stage is pulling against just the trigger spring and then the second stage is pulling against that plus the disconnector spring for the last little bit. |
I just got 4 more new Yellow Tavern reduced power trigger/hammer/disconnecter spring sets from Brownells. All 4 sets have red overspray painted springs. Tom 
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I just looked over the different 2-stage triggers and I don't like the idea of the KAC and Giesselle having adjustment screws. With loctite the chances of the screws coming out are slim, but its just not something I'd put on a battle rifle. The RRA would have been a nice durable setup if they'd reduce the pull weight and somehow fix it so there's no chance of it becoming a single stage w/o requiring "tuning" with a file, and they should have fixed the disco pin issue at the factory. A lifetime warranty isn't too helpful if your rifle can no longer fire out in the field. Something like the KAC/Giesselle w/o adjustment screws, and not having a separate disconnector pin would be the answer. FYI, someone else that has had a RRA 2-stage turn into a single stage: HERE |
It's there to prevent the hammer from striking the firing pin in case of disconnector failure. The notch will get stuck on the firing pin rim. |
You dont think its odd the US military disagrees with you? This type of reasoning always reminds me of when guys used to say they would not use battery powered optics on a battle rifle. |
So are you implying the US military uses set-screw adjustable 2-stage triggers on their MBRs that can fail completely or become single stage triggers after awhile? Or are you implying that the US has used 2-stage triggers in the past with their MBRs? My qualms with the AR 2-stage triggers are with the various designs, NOT the fact that they are 2-stage triggers! I have read debates where the subject was INDEED about the validity of using a 2-stage in the field, but this isn't one of them!! 
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The KAC trigger for example doesn't become unsafe or unserviceable even if both set screws come out. It's not used on battle rifles though, I think it's used in Mk12 only. Not sure about who uses the KAC auto triggers, probably HSLD units only. |
The US Army uses KAC triggers in the M16-based Squad Designated Marksman Rifle, which is issued to Squad Designated Marksmen in regular infantry units. Not just HLSD commando-types. SDM Rifles go through the same exact operating conditions and rigors as the average M16 or M4 in an infantry squad/platoon/company because the SDM is a part of an infantry squad/platoon/company. The Army Marksmanship Unit, which is responsible for the development and assembly of the SDM-R, is currently evaluating the Geissele trigger and have reported right here that they are favorably impressed. I would not be surprised at all if the Geissele trigger becomes a part of the SDM-R specification in the near future. |
He's talking about the notch on the bottom, where the trigger-sear surface is on a regular AR trigger. (Just below the hammer spring leg, straight down from the "m" in "adcofirearms" in this pic.) |
Never thought about it, but could be it's there to prevent hammer strike in case of sear failure. |
The RRA has to be "tuned" with a file because it doesn't have the screw adjustments. So instead of being able to fix it with an allen wrench w/o taking the trigger out of the rifle you have to pull it out and disassemble it. All three use the same principle to provide the second stage so theoretically all three are subject to the same loss of the second stage. That the RRAs--which by the no-set-screw logic in this thread should be the most reliable--are failing, and the KAC and Gieselles are not tells me that the quality of the materials and construction means more than the design. The military is OK with the KAC and its set screws. And losing the second stage won't keep it from firing, just possibly make it unsafely light. (If it's like my dad's the first stage is only 1-1.5lbs. A properly balanced one would have more like 4-5lbs on the first stage so it would degenerate into a long single-stage.) The JP single-stage has set screws too, but if they back out they just move the trigger in the direction of having more pretravel(creep) and more overtravel. It becomes like the stock trigger. |
The filing is not needed until after a few hundred rounds or so from what I have read. They always seem to take awhile before it becomes a long "single stage". This leads me to believe something is wearing out or the springs or wearing out, but I can't figure out why this would cause the single stage problem, and why filing the disco fixes it unless the disconnector itself was wearing out. In addition, as I mentioned already, RRA should have upgraded the disco pin from the factory. I am not talking about the tuning WOA performs on the RRA 2-stage trigger. I didn't know about the KAC operating just fine w/o set-screws. However, having set-screws in the first place kind of makes it a match setup more than a military/battle rifle setup. If the set-screws come loose a bit, it can affect trigger feel - which can be important for the purpose of which said rifles were procured for the designated marksmen. It'd be probably more adoptable by .MIL, if KAC or Giesselle triggers were made in a single stage non-adjustable version with a set trigger pull weight designed to work well in a match/competition rifle, but fool-proof enough for .MIL use. E.g. 2-3 lb single stage trigger designed for mainstream M16/M4/AR15. |
High Power requires 4.5lbs. Accuracy Speaks makes a single-stage, non adjustable that comes in right about there, but I'm sure he's hand-fitting them maybe tweaking the geometry slightly. If .mil wanted to give the average soldier a better trigger they could change the pull weight range in the specs to 5-6lbs instead of 8-12 or whatever it is now. That would force the manufacturers to be more careful fitting the triggers and/or change the geometry and/or springs. If they simply changed springs it would increase the risk of light strikes. If they changed the geometry, parts wouldn't be compatible with current parts, which is probably unfeasible for such a large inventory. |
Why do you think that two stage triggers are not appropriate for military use? WTF do you think was in every Mauser k98, M1903, M1, and M14 rifle ever made? With every post you make less and less sense. Why don't you just call the AMU and tell them they don't know shit about building rifles for war? |
Apparently .MIL does not think 2-stage triggers are appropriate for the M4/M16 if the TDP calls for a single stage trigger (Source: You on Page 5). Unless the DMRs are going to be mainstream issued, then the average rifleman isn't going to be using a 2-stage trigger (KAC or Giessell or otherwise). Our of curiosity, did the K98, 1903, M1, and M14 2-stage triggers have set screw adjustments from the factory? I'm searching for pics right now. I would find it hard to believe the modern US military would approve of set-screws on FCGs issued for mainstream use. It has to be absolutely foolproof. I never said there was anything wrong with using a 2 stage trigger on a MBR. Go and read page 5 where someone attacked me for the same reason. |
Yes (search the archives or use search, it rendered the trigger useless). and someone just recently had the single-stage thing happen to his RRA 2-stage. As I suspected, something must have been wearing to cause the single-stage effect. The disco spring would have to take a significant set to allow the disco to drop down, which is unlikely unless the spring is cheap chinese steel. If the RRA 2-stage were current issue (as-is), someone evaluating the RRA FCG would/should specify that the peened pin be replaced with a solid hardened steel pin long enough that it wouldn't fall out accidentally. The surfaces (if not the entire hammer) should also be spec'd for a certain hardness and material to prevent the need for "filing". |
Let me give you a brief refresher on how the M16 came into being: 1) Eugene Stoner designs AR10 with no input from the military 2) Armalite designers submit scaled down AR10, called AR15, to military trials for a small caliber rifle. 3) The Army is forced by the DoD bureaucracy to adopt Armalite's design without many of the changes the Ordnance Corps wanted and saw as necessary. 3) M16 had many failures in the field, some of which were directly traceable to the features requested by the Army but vetoed by DoD. Since every rifle designed by Springfield Armory has had a two-stage trigger as standard, anyone without his head stuck in his rectum could see that the .mil weapons establishment has considered two stage triggers as desireable for over 70 years. Furthermore, the absence of a two stage trigger in the AR15's design is due to the fact that the rifle was not designed by the .mil, nor designed to specifications laid out by the Ordnance Department. I would not be surprised in the Marine Corps had requested a two-stage trigger for the M16A2 and got left on the table for budget reasons, or some other reason having nothing to do with their suitability for combat rifles. One final factoid: the combat suitability of two stage triggers in semi-automatic and select-fire rifles has been proven beyond any argument by the M1 and M14 rifles. |
Where can I find info on this?
So it took nearly 40-50 years before someone developed a 2 stage FCG suitable for combat in the M16/M4? 
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| My point in the last statement is that given the past trend towards favoring 2-stage triggers in combat use in the US military, albeit not modern US military, why did it take 40+ years for a vendor to develop 2-stage FCGs that are getting rave reviews by such and such members of the military? What happened in the past that took so long for this to happen? |
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This is starting to get pretty far off topic. I think we've established that all US military rifles prior to the M16 had 2-stage triggers and I don't think anybody is doubting whether the 2-stage trigger in general is appropriate for military use (at least not on this thread). I suspect that the real reason the M16 has a single-stage is because it was chosen by bean counters and the single-stage is cheaper. It's also, I believe, the first rifle adopted after the studies that showed that nearly all shots actually fired in combat by an average soldier are at close range and mostly unaimed, so the army side didn't fight hard for a trigger designed for precision fire at longer ranges. Obviously they do see the value of the 2-stage match trigger for guns that are designed for precision fire. Now the question is whether or not a trigger with set-screw adjustments is suitable for combat use. There seems to be a lot of knee-jerk "OMG it has a set screw, that could come loose, can't use that" responses, with no consideration of anything else. (Reminds me of the "OMG that sight takes a battery, they die, can't use that" responses to optics.) The RRA failures clearly show that absence of set screws does not automatically make it reliable. And the non-failures of all of the KACs in SPR/DMR/SDM/etc. rifles clearly show that having them does not automatically make it unreliable. Seems to me that being able to adjust the trigger for a good pull would improve the soldier's ability to get shots on target, and that's a good thing. Being able to adapt/correct for wear by simply turning a screw vs. removal and filing would get the gun back in action quicker, and that's a good thing. Measures like loc-tite can minimize the risk of them losing adjustment. And the Gieselle trigger seems to have gone to extreme measures to make sure that nothing "bad" happens if they do come loose. Given a choice between having a "good" trigger that might become a "bad" trigger if the adjustments come loose vs. having a trigger that's "bad" to begin with and not adjustable I'll take the risk on the good one. |
The civilian competition market is probably the largest, most influential group when it comes to firearms development/enhancement. The M16/AR15 hasnt been part of that market for very long. Until more and more folks started shooting AR type service rifles, no one really cared about the triggers.... |
Geissele if you have the coin, Rock River if you don't. For every story of a Rock River 2 stage trigger failing, there are thousands (if not tens of thousands) that work, and work, and work, and work. And even if they fail, they just become single stage triggers which makes it a fail-safe design. BTW, before I switched to Geissele, I ran a RRA for just over 5K rounds in three years of use. Not a single failure. Ever. |
Well, thats what I have and it works so far, just heavier then I like. |
I assume you mean RRA. Is it too heavy overall but balanced OK, or balanced too much to the second stage? If the latter, then John at WOP should be able to tune it more to your liking for $30. |
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Gents, Ill jump in here a bit with my limited knowledge. I designed my Hi-Speed trigger with no input from the Military; I only had my Highpower experience and general firearm background. When I showed it to the AMU they said that they had recently been discussing triggers as they had a limited supply of MKs and were not happy with the 2 stage trigger that is available (they actually replace the $300 trigger after 3500 rounds in a combat weapon). What they liked about the Geissele trigger is the screw adjustments and the fact that it can use stock springs. As a future project I was going to combat harden the Hi-Speed to get rid of the screws as I thought that screws are bad for combat. I was told this is NOT the case and the AMU wants the ability to adjust the sear to account for any wear. (which is extremely minimal on the Geissele trigger: 100k rounds/cycles with no adjustment needed and no loosening of any polymer sealed screws). My opinion (repeat: my 2 cents) is that I can not make a traditional single stage trigger that would meet my standards for crisp letoff. A properly adjusted sear on a Geissele trigger hangs on 0.003-0.004 when the 2nd stage comes up. A single stage trigger with this sear overhang would work but it would not be reliable and we would see the recurring, occasional post that keeps coming up "My xxxxx trigger went TU". On the other hand, with additional sear overhang the trigger would be creepy. (This is where the beauty of the 2 stage trigger comes in: you get the best of both worlds). There are three R&D projects in the works here that should be available in about 3-5 months. Bigbore has a preliminary prototype of Project2 and he gave me some great feedback which I really appreciate. I think the 3 projects will cover just about everybody's concerns with the current state of the art. Bill_Geissele |
"limited knowledge" - that's funny Thanks for posting (great info) but what a tease! No insight into the upcoming projects?  Maybe one is a non-traditional single stage trigger that meets your standards for crisp letoff? |
I appreciate Bill's efforts and it appears he's well on track!
At least I wasn't alone in initially thinking the screws are bad for combat. In retrospect, this is probably why my Vepr 2-stage started giving me nasty trigger slap only after being "broken in" (1000+ rd). It does not have any set-screw adjustments to account for wear on the engagement surfaces (but the Red Star / Power Custom unit does, IIRC). The "failure" rate of the Vepr/Robinson 2-stage is similar to the RRA 2-stage. You hear about 1-2 people geting trigger slap with the RA unit, and then 5 more step in to say "it didn't happen to me..."
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Holy Sh!t!! I just received my RRA 2-stage from Steve, installed it and it is GREAT! I can't believe the difference. Until reading this thread, I didn't understand how a 2-stage trigger worked differently and how it could feel so much differently. Well, I learned, I ordered and now I know! |
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