The Original CZ Forum
CZ LONG ARMS => CZ Scorpion EVO => Topic started by: DanT on February 15, 2017, 01:49:52 PM
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Comment 4/10/2017: This thread is a continuation of an earlier one. If interested, also see:
http://www.czfirearms.us/index.php?topic=86073.0
- DanT Phoenix, Az
After fine tuning the trigger pull length and reset distance, the trigger "over travel" became more noticeable.
There is a "over travel" foot on the stock trigger on the front left of trigger. Adding a small foil shim removed the over travel. Add too much shim and the trigger will not "fire". Start by adding too much, then reduce the number of foil layers until the trigger starts working again. Glue it into place with some quick set, two part epoxy. I used the quick set version of "J-B Weld", "J-B Kwik".
Pretty simple adjustment.
(http://i38.photobucket.com/albums/e108/JWLazer/overtravel%20fix_zpssx2a7e2a.jpg)
The above is a composite of four modifications to the stock trigger:
1) 0.0075" aluminum foil shim under the "over travel" trigger foot. No more over travel.
2) 0.025" brass shim under the disconnector foot. Short trigger reset
3) ~0.30" brass + aluminum foil shim under the rear trigger feet to shorten the trigger length
4) In order for the safety to now work, 0.015" was removed from the top of the rear trigger foot.
It seems to work pretty well. When I figure out how to upload the demo of the trigger performance, I will add it to the next post.
DanT Phoenix, Az
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Ok, another "do over" on the video. After further review, the first one seems a bit silly with very little information.
Sorry, the focus is not great at the start, but it does come into focus later on. The pictures above are better than the video to see what it looks like inside.
https://youtu.be/BxKcEOJr9Bo
I am really happy at how well it is working now with short trigger pull, short reset, plus removal of the trigger over travel.
If anyone wants me to do this to your trigger, message me.
- Dan T Phoenix, Az
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Thanks for the nod to JB kwik weld. As you recall, in the other thread I was thinking a small welding blob. Seems like JB should be cleaner. Instead of using shims, I plan on putting a small blob of JB under the trigger and disconnector feet, letting it set, then filing it down to the proper travel distances. I'm thinking it has the same effect as using shims. I mean, it doesn't matter if you add metal at the bottom (shim) or top (bottom of foot), right? Any thoughts or concerns with that approach?
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That seems like it could work. If a shim were to fail, it would simply cause increased margin once again (i.e., "fail safe"). I prefer to epoxy to the painted surfaces because it is a bit easier to force them to release the next time I want to change things.
However, at this point with the remaining trigger over travel fixed, it is as good as it can get.
- Dan
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how safe/reliable is all this modifying a fully field tested trigger system with glues and shims, and blobs...
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You folks are braver, or more experienced for sure (or crazier) than i am. I can replace springs, maybe even polish a surface or two, but this...? Kinda falls into the "Professional Driver on a Closed Course" category for me. Very interesting info, though
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Others are making similar modifications, but changing the metal parts themselves.
Take a look at this just past the 6 minute mark.
https://www.youtube.com/watch?v=ln_ScGTBIVo
Very sporty. Here are the trigger kit parts as pictured:
https://czcustom.com/czc-parts-made-in-the-usa/cz-evo-trigger-pack-czc.html
This parts kit has pre-travel/over-travel adjustment screws, smaller trigger hooks (shorter trigger travel), a shorter rear hammer shelf (shorter disconector travel), and has the needed safety offset built into the trigger part.
One is a set of new custom parts (hammer/trigger), the other is a set of custom shims. They are both performing similar functions. One is fixed, the other is adjustable. One is prefabricated (nice!), the other is custom built.
However, in either case, margin has been removed in order to provide higher trigger performance. The stock trigger has huge margins: 10 lb. trigger weight, very long trigger pull, and very long trigger reset. With the shim approach, you can set the performance to whatever level you wish. What is shown is much, much better than a stock trigger, but it is not match grade. I think a fundamentally different trigger design would be needed for that.
It comes down to what you like in a trigger. Lots and lots of margin, or shorter, higher performance. I have some custom CZ pistols (from the CZ custom shop). I like higher performance triggers.
In the case of the changes I have outlined above, the shim sizes could be reduced to introduce additional margin (longer pull/reset) to fit personal preference. As I have said in an earlier thread, the shims (particularly the reset and trigger pull) can be prototyped completely out of folded aluminum foil shims to allow you to get a feel of the end performance at no risk other than wasting some kitchen aluminum foil.
It is nice however, when the performance is exactly what you want, to measure the thickness, find the closest available larger metal size (like 0.032" brass -> 0.030" or 0.008" brass -> 0.007"), and then file to fit. I plan on doing that with my rifle, but have not gotten there yet.
The use of epoxy to hold the shims in place is not a problem. I have to put it on the top to keep it from raising the shim and affecting the thickness. Thus the "blob". Try to take the front barrel off and see how well mere Locktite works holding things together. Epoxy is quite a bit more substantial than that.
- DanT Phoenix, Az
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Have you shot it with the mods to the trigger. I wonder with a short travel and reset if doubles and/or unintentional bump firing would occur, especially with gloves on.
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Have you shot it with the mods to the trigger. I wonder with a short travel and reset if doubles and/or unintentional bump firing would occur, especially with gloves on.
I have taken these changes to the local range (C2 tactical) to test them. It is not a problem.
I would think using gloves you might want more margin. That is not a problem. The shims can be sized to fit the margin.
If you want, you can take a very simple half step that leaves lots of margin in place and requires no other changes to the trigger. The original change I made used 0.016" brass shims for both the trigger shim and the disconnector shim. This removes 41% of the long trigger pull and roughly half of the long reset. That change is still a big improvement.
0.016" brass strips is a standard size, so it is easy to get. 0.016" on the trigger foot requires no filing changes to the top of the rear trigger foot as the safety just clears. Here is a shot of the trigger when I had 0.016" shims in place for both the trigger and the disconnector:
(http://i38.photobucket.com/albums/e108/JWLazer/pic10_zpsbn06yvse.jpg)
That is a dead simple drop in with lots of margin. You just need to place the shims and "blob" them in place, catching the top of the shim and the metal around it. "Blobing" epoxy over the top (rather than under the bottom) keeps the thickness right, especially for the rear trigger shim. With this setup, the trigger over travel will not be noticeable, so there is no need to put a shim in place there.
If you don't like it, you can pull it back out and have zero changes to the trigger. However, if you then decide you want more, you can pull it out and put these larger changes into place.
If you want, ping me and I can send you these two 0.016" shims for a couple of bucks. However, 12" long, 0.016" thick brass strips are very available on amazon.com. The rear trigger shim is a bit over 3/4" long (7/8"?) by 1/8" wide. The disconnector shim is 1/4" long and 1/8" wide. The dimensions are not at all critical, just the thickness, 0.016".
- DanT Phoenix, Az
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At the range this morning, I got a "double". I.e., two bullets for the price of one pull. That means the disconnector shim of 0.025" was a bit too much and did not quite catch all the time.
I don't really want to file the 0.025" brass shim down to 0.020", so I have ordered some 0.020" brass sheet for a thinner disconnector shim. In the meanwhile I dropped back to the 0.016" disconnector shim I was using before, while still using the 0.030 to 0.032" trigger shim.
So until I get the 0.020" brass stock, the reset is not quite as short, but still works with the short trigger travel. However the longer reset length does have a side benefit. The 0.016" reset shim causes the rear trigger shelf to just "bump" the disconnector right before firing the trigger. That "bump" can be felt in the trigger as a bit more resistance just before firing. It makes it "feel" like a a two stage trigger (some trigger take up, then a bit more resistance, immediately followed by a trigger break). It is kind of nice to feel right where the trigger is going to fire.
Disconnector fully applied (left hook on trigger shelf) using 0.025" shim (wrong side of marginal):
(http://i38.photobucket.com/albums/e108/JWLazer/0.025%20reset%20before_zpsnuck0yif.jpg)
Disconnector fully applied (left hook on trigger shelf) using 0.016" shim (very robust):
(http://i38.photobucket.com/albums/e108/JWLazer/0.016%20reset%20after_zpsbuiintvw.jpg)
0.020" would be halfway between the two. I think it is good to visually see the difference between "just barely marginal" vs. "very robust"
Here is today's "final" view:
(http://i38.photobucket.com/albums/e108/JWLazer/crop_zpsqcejsgzg.jpg)
I figured out that I only needed a small shim under one of the two rear trigger feet (not both). Less shim, more "blob". That makes for a smaller, lighter shim that is less likely to "let go" under recoil.
Bottom left: 0.007" trigger over travel shim
Middle: 0.016" disconnector shim (a common brass thickness) - robust, but may move up to 0.020" (less common brass thickness)
Bottom right: 0.032" trigger shim (a common brass thickness)
plus a HBI disconnector spring, softer trigger spring, and 0.015" removed from top of rear trigger (upper right) for clearance for the safety.
- DanT Phoenix, Az
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I did a better job with the overall travel. I got some 0.013" metal sheet in today and it still allowed the trigger to fire when used as the over travel shim. When you go too far with the overall travel shim, it will block the trigger from firing.
The trigger fires at around 0.039". If we have 0.013" of over travel on top of that, then the total trigger travel length is at least 0.052".
The "simple, conservative" change is 0.016" for the trigger shim. That is removing 16/52 or 31% of the total trigger travel. However, since the over travel is so long, removing 0.013" of over travel on top of that means that overall 55% of the total trigger travel (0.013" + 0.016" removed) be removed by also cleaning up the overall travel.
Over travel is not really a useful margin from a safety point of view. It does help manufacturing by allowing a bunch of manufacturing variation and still have a working firearm. However, it does not help safety. Getting rid of the overall travel "tightens up" the feel of the trigger quite a bit without giving up any "safety" margin.
Thus, the conservative setting can remove 55% of the total trigger pull length. This is:
0.016" trigger shim
0.016" disconnector shim
0.013" trigger over travel shim
No metal removal needed for clearance for the safety.
The "sporty" setting looks like:
0.032" trigger shim
0.016" disconnector shim
0.013" trigger over travel shim
Plus metal removal for clearance for the safety
This leaves roughly 0.008" (plus a tiny bit of over travel) out of 0.052". This removes about 85% of the trigger travel.
15% trigger travel (sporty) vs. 45% for conservative. I supose you could set the trigger shim to 0.025" and get something in between these two (29% trigger travel - less metal removal needed).
I guess the main message is that removing over travel can tighten things more than I initially thought. That is potentially 20% of the trigger travel for nothing from the user point of view. The trigger travel is now a bit tighter than the video for the "sporty" version.
- DanT Phoenix, AZ
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Nice write up DanT always good to see others not afraid to dig in and make things work
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Someone wanted to see the trigger in action. I got my wife to grab some video for me today at the range. My son and I are both casual target shooters, so we are not speed demons.
5 shot warm up at 25 yards. No optics, no bench rest:
(http://i38.photobucket.com/albums/e108/JWLazer/84aed4f3-2f13-44cb-8428-1e5045951629_zpsk0ucjj1q.jpg)
My son and I:
(http://i38.photobucket.com/albums/e108/JWLazer/us%202_zpsdpnjtvph.jpg)
Here is my son Matt punching paper at the maximum indoor range limit of roughly 25 yards.
(http://i38.photobucket.com/albums/e108/JWLazer/Matt_zpsevqeggvc.jpg)
https://youtu.be/rYOtOhp852Y
He has only fired an earlier version of the trigger and very much likes current the improvements.
- DanT Phoenix, Az
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I had a shim break loose in an extended test. I guess it is time to scrub the paint off under the shims, ruff up the shims and the metal, and try using a bit of epoxy under the shims.
I will have to give it a day to harden and give it another try.
It is shear force that is at issue. The shock is being applied from the side, not the top or bottom. I image some glues would be better at that than others, but that is not my specialty.
Anyone have any idea what would be the best glue here? I am using the quick version of JB Weld. Would super glue be better? Other recommendations?
- DanT Phoenix, Az
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I did some looking on line for the best metal-to-metal glues.
"I've used JB-Weld in some situations where I thought "There's no way in hell this is going to bond" and it came through. Stuff like fixing bike frames and holding a fair amount of my old Volkswagen Vanagon together."
"Agreed - HOWEVER - J-B Kwik doesn't have a very good shear strength; use Weld, or *if* you can find it, Industro-Weld also by the J-B Weld company (of Sulphur Springs, Texas)"
Alas, I just used J-B Kwik...... Shear strength is what I need. I will have to see how the J-B Kwik works out. If it lets go, I will drop back to slower curing J-B Weld.
- DanT Phoenix, Az
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Dan--you did a great job! I'm so glad we have people like you that know how to do this type of stuff.
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I have been making the shims smaller thinking that less mass might reduce the problem with them "letting go" under recoil. This approach was not working as I was having problems in particular with the rear trigger shim and to a lesser extent the disconnector shim as well.
As I was pondering this, I think I figured out problem. 95% of a solution is a good understanding of the problem. That way I can attack the root cause (why?) vs. the symptom (the shim breaks loose).
Play with the trigger assembly. "Fire" the hammer, then with the trigger still held all the way back, press the hammer back into place. The hammer is caught by the disconnector. Hmmmm.....
Consider that with a "full auto" trigger pack, the evo is rated at about 20 rounds per second. That means the firing sequence is really getting that hammer moving with quite a bit of energy, even for us who are only firing one shot at a time.
"Catching" the mass of the hammer, especially in the actual firing sequence is quite hard on the disconnector. I have seen posts were certain versions of the disconnector have actually broken due to this "catching" stress. The disconnector is not the only thing being affected here. The disconnector shim also absorbs this "hammering", which can break the epoxy bond.
I see the CZ custom shop hammer has a big hole in the middle of it to reduce the weight. Likely, this speeds up the time from trigger release to impacting the firing pin. In view of the pounding the disconnector takes catching the hammer, I can see where lightening the hammer would be helpful to reduce the pounding going on to the trigger assembly.
Likewise, after the hammer is "caught" by the disconnector, releasing the trigger causes the disconnector to release, releasing the hammer, which then is "caught" by the trigger hooks. You can hear the trigger reset as it seems to catch with a lot of force. This is the force of the trigger spring plus the force of the hammer spring plus the force of the firing pin safety as applied to the lever arm near the hammer accelerating the weight of the hammer into the trigger hooks. The trigger hook then instantly stops the hammer acceleration dead in its tracks until the next time you pull the trigger.
Again, this "catching" action by the trigger hooks is carried to the rear trigger feet. This "catching" action is like "whacking" the rear trigger shim with a small hammer each each time the trigger is released and the trigger hooks need to catch the rapidly accelerating hammer. The force of this acceleration can be felt if you try to stop the trigger from "snapping" forward after the trigger reset.
Thus the problem is not "recoil shear force" like I originally thought, but rather pounding from the trigger and disconnector feet onto the top of their shims.
Thus, it seems to me the solution to this problem (pounding of small trigger/disconnector shims until the epoxy breaks) is to use a physically longer and wider shim. Thus, even if the epoxy directly under the trigger and disconnector foot were to be pounded to dust, the metal further away from the point of impact would remain firmly anchored down.
At least that is the theory.
The trigger over travel shim does not take any pounding (just the user trigger pull force) and thus can remain fairly small.
The shims I first started out with were longer and wider and seemed to work fine, but the more problematic ones lately have been the smaller versions.
From what I am reading (see 3M white paper http://multimedia.3m.com/mws/media/774716O/mechanicals-versus-structurals.pdf?&fn=MechanicalsVsStructurals.pdf), "modern" two part, slow drying epoxy glues can be better than screws, rivets, spot welds, or welds. JB Weld falls in this classification with a gripping power of almost 4000 PSI. These shims are stoutly attached.
Here is the trigger shim (0.032") and smaller trigger over travel shim (0.013")
(http://i38.photobucket.com/albums/e108/JWLazer/trigger%20frame_zpsjuzodni4.jpg)
Here is the disconnector shim (0.016") on the trigger shelf. It could perhaps be a bit wider:
(http://i38.photobucket.com/albums/e108/JWLazer/disc%20shim_zpsqn4hjt6q.jpg)
Excess epoxy is shown here. After a few hours the slow dry epoxy gells up and the excess can readily be removed with a toothpick.
Here is everything thing in the trigger assembly after clean up and drying overnight. The rear trigger shim is deliberately just short of the second trigger foot. I want pounding from one end only, not both ends.
(http://i38.photobucket.com/albums/e108/JWLazer/New%20shims_zpssxyh4vju.jpg)
I will run it by the range and see how it does probably Monday.
- DanT Phoenix, AZ
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The shims did well at the range today. Nothing broke loose. There epoxy around the shim near the trigger and disconnector foot seem fine. The larger, wider shims are looking good. I will get one more chance to take it to the range before things get super busy at work.
Just for more information, here is how the trigger hook look on the front hammer wing for different trigger shim heights. First, no trigger shim (top), then 0.016", 0.025", and lastly 0.032" (current configuration) on the bottom:
(http://i38.photobucket.com/albums/e108/JWLazer/trigger%200%20shim_zpshm3sg1bp.jpg)
(http://i38.photobucket.com/albums/e108/JWLazer/trigger%200.016%20shim_zps1xei4la0.jpg)
(http://i38.photobucket.com/albums/e108/JWLazer/trigger%200.024%20shim_zpsqklwvytc.jpg)
(http://i38.photobucket.com/albums/e108/JWLazer/trigger%200.032%20shim_zpssvmbnen2.jpg)
The 0.032" case above is not hair trigger and I don't want it to be. I would be concerned about how well the safety would work with a "hair trigger". There is still a fair amount of trigger travel required to fire the hammer, but much less than the stock configuration.
For comparison, here is a shot of the CZ Custom Shop trigger hooks on the front hammer wing:
(http://i38.photobucket.com/albums/e108/JWLazer/Trigger%20CZ%20Custom_zpsmvdppmsw.jpg)
Oh, well... Work is going to get in the way of fun for a while for me.
- DanT Phoenix, Az
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Thanks Dan , for all the info on the scorpion trigger.
The angle on the hammer vs triggerhook looks kind of strange to me...
I would have to see it in person when i get Mine.
Keep on the good work!
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The trigger hook angle is the "positive engagement" that makes the trigger safe. As you pull the trigger, a safe trigger hook angle "cocks" the hammer back a bit. Changing the hook angle such as to "just barely" cock the hammer is a trick to lessen the apparent trigger pull as you are fighting the hammer spring less by doing less "cocking".
It is unsafe to have the hammer move forward towards "firing" as the trigger is pulled.
There is no way I am going to modify that trigger hook angle. I don't want to screw it up and have to shell out $90 for a new trigger. The trigger pull weight is fine as it is.
I got to the range a second time this week, and shims still look great. I think this is a keeper.
- DanT Phoenix, Az
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I have now made many trips to the range, and the latest trigger shim mods (0.032" brass rear trigger shim, 0.016" brass disconnector shim, and 0.013" over travel shim) are solid and work very well.
These metal shims were made from brass trips I found on amazon.com. I spend perhaps $20 on the metal for these three shim. Very little metal is needed. The brass typically comes in 12" strips. 1/2" or 3/4" wide stock is fine.
Using JB Weld (the slow cure formulation) rather than JB KiwK (the fast cure formulation) fixed the problem I had with the shims breaking free. I just made sure I roughed up both sides being glued and clamped the shims when I glued them to make sure the glue did not add to the thickness. These shims are now not coming out willingly!
It was not easy to clamp the disconnector shim without removing the trigger (the trigger is in the way for clamping), so it ended up too thick. I had to file that shim down to get the disconnector back to the point where roughly 50% was in contact with the hammer shelf. If I did it again, I think I would find some way to apply weight to the top of the disconnector shim while it is being glued in order to get it closer to the desired spacing.
If the disconnector shim is too thick, the rifle will fire "doubles" as the disconnector does not have enough "bite" on the back of the trigger shelf to reliably stop the hammer when the receiver cocks the hammer after firing a shot. The shim then needs to be filed down to get enough rear shelf "bite" to stop the doubling.
If I measure trigger movement by changing the size of the shim at the back of the trigger, this is what I see as I reach the end of this modification:
0.032" used for initial trigger "take up reduction"
~0.014" from this point to tripping the trigger
~0.015" of trigger over travel after firing the trigger
Thus, from the rear of the trigger, there is about 0.060" of total travel in my stock trigger. Taking out the 0.032" rear trigger shim and the 0.013" over travel shim, about 0.015" remains. Thus these modifications have removed about 75% of the total trigger travel, and about 70% of the trigger travel before the trigger fires.
The trigger is not "hair trigger" since 30% of the travel is still left, but is very much improved (and predictable!) from the very long pull that the rifle had when I first started out.
- DanT Phoenix, Az
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I was only in there long enough to polish the edges of parts that rotate or rub, and mildly go after the disconnector face where the hammer butts into it during the trigger pull. But, why not drill, tap, set screw to get where you need to be? The disco foot has enough material to punch straight through the bottom out through the top, tap, install screw. And be able to adjust it with the hammer discharged and the lower popped out. I would use red loctite on the screw but you would be able to have it all installed and adjust it, while the loc-tite was drying still. In other situations a small tack from a welder is what I have done. And then just ground it to where I wanted it exactly. Or through drilled as mentioned above, and installed a bit of drill rod and tacked over the top then ground the protruding face to exactly where I wanted it. (On other FCG's)
Because this functions very similarly to an AK FCG, aside from that absolutely poor multi-purpose trigger return spring that adds a ton of weight. The parts interactions seem extremely familiar to me. I was able to hack the weight almost in half by simply pinching the trigger spring to take some of the preload out of it. And grinding the disco face back at the same angle as stock, so it has less material interaction with the hammer, without compromising the engagement surface. (And paste/grease lubricant) I did break the upper horizontal edge of the nose of the hook. As it had a distinct flat nose. But did not cut the nose back or interact with the hook portion at all. I may. And I definitely have re-cut plenty of disconnectors to make them 2 stage or not before.
I am very happy that you have the majority of the necessary dimensional changes worked out with shims. But I don't see shims/glue as a viable long term solution for the reasons you have already found. If you're dead set on using shims. Use steel shims and then spot weld them to the trigger pack housing. Finish with a file. I haven't found epoxy to really last in an environment that is in constant contact with solvents/lubricants. And I like my FCG's coated in a lubricant paste.
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Actually JB Weld is not a typical epoxy. It is often used in automotive engine repairs in a hot, dirty, greasy, oily environment with high level of vibration. Sounds perfect for a gun. I have seen in the rimfire forums where JB Weld was used to add "metal" to a 10/22 trigger part. I have heard it being used to fix broken bike frames. It is very tough stuff. Not all epoxies are created equal.
Actually, I was motivated to use the shims because I thought that this approach would be a bit more accessible to the average enthusiast who might own these guns. Welding, or drilling and threading have a much higher risk of ruining a $90 part than gluing a shim in place. This modification can be done for under $20 using some tin snips and some metal strips from Amazon.com.
- DanT Phoenix, Az
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I performed this full mod, with .032 pre-travel shim, .016 disconnector shim, and .013 overtravel shim on my SBR and it works extremely well, no doubles tonight in around 80-100 rounds, and a dramarically better overall pull, immediate reset, etc. Felt much faster to run, and absolutely much more pleasant to dry fire. Thank you DanT so much for your work and research on this method of trigger adjustment, it saved me $200+ on going the cz custom route.
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I performed this full mod, with .032 pre-travel shim, .016 disconnector shim, and .013 overtravel shim on my SBR and it works extremely well, no doubles tonight in around 80-100 rounds, and a dramarically better overall pull, immediate reset, etc. Felt much faster to run, and absolutely much more pleasant to dry fire. Thank you DanT so much for your work and research on this method of trigger adjustment, it saved me $200+ on going the cz custom route
I am glad it worked well for you. It has been a great improvement for me. If anyone wants a set of shims, private message me and I can cut up a few and send them out a few for a few bucks.
(http://i38.photobucket.com/albums/e108/JWLazer/Shim%20pack_zpscvbrk6nl.jpg)
- DanT Phoenix, AZ
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I'd like to give a shout-out to DanT for coming up with this awesomely simple and inexpensive mod.
I'd also like to offer up another option for this mod (with his permission). This mod won't be as ideal as the original one with the three shims, but it's a simple way to decrease the trigger reset distance.
First I made two 45 degree cuts in the FCG housing, then used a crescent wrench to bend the inside rear cross section up a bit. The metal being bent up takes the place of the rear shim. I then took the housing to a belt sander (a file will work too) to flatten the bottom (when you bend the rear cross section, it also protrudes down in the rear a tad). Adjust the amount of bend as necessary and clean with a file. Cold blue and oil and you're back in business :)
It may be possible to do the same thing under the forward trigger stop, but I have not tried that. Yet.
Thanks again to DanT for the initial work!
(http://i268.photobucket.com/albums/jj2/medphys3/1062D735-1C2F-4AB3-85D1-34A837232CB9_zpsa3cxhbq6.jpg) (http://s268.photobucket.com/user/medphys3/media/1062D735-1C2F-4AB3-85D1-34A837232CB9_zpsa3cxhbq6.jpg.html)
(http://i268.photobucket.com/albums/jj2/medphys3/F275AFCC-F904-45BF-BDBD-77AF10B0A4D9_zps9q9slzmc.jpg) (http://s268.photobucket.com/user/medphys3/media/F275AFCC-F904-45BF-BDBD-77AF10B0A4D9_zps9q9slzmc.jpg.html)
(http://i268.photobucket.com/albums/jj2/medphys3/C954FC64-D0AE-41E6-BFF1-B0913A6AB92A_zpsnaa4qhnv.jpg) (http://s268.photobucket.com/user/medphys3/media/C954FC64-D0AE-41E6-BFF1-B0913A6AB92A_zpsnaa4qhnv.jpg.html)
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I just wanted to throw in my 2 cents worth on this excellent modification done by DanT. I obtained a shim kit from DanT and added them to my trigger pack after dry fit testing them. After I was satisfied the shim sizes put the engagement points close to the desired settings I glued them all down with JB Weld. I reassembled the trigger and worked through function checks. The JB Weld does add thickness no matter what you do. If you clamp it too hard then the bonding layer is too thin and may crack and fail. Lightly clamping the shims in place is best. The added thickness caused the over-travel shim to block the hammer release. With slow application of a jeweler's file I reduced the thickness enough to allow the hammer to clear the trigger sear. Both the primary and disconnector sear engagement was reduced by ~40%. This is allowed for a more than adequate reduction in trigger rearward and reset travel while maintaining safe engagement. Once the trigger pack was placed back into trigger housing and the safety levers installed, it became apparent the trigger pre-travel shim needed to be thinned down slightly to allow full safety engagement. Again, a little filing and slowly checking progress fixed the issue. The end result was surprising!!! Easily made the biggest improvement in my Scorpion since adding the HBI springs. The trigger is responsive with minimal pre-travel, clear and short reset. I just wanted to say thank you to DanT for posting this excellent modification! I plan to take it to the range shortly and test it out during live fire. If there is any revelation afterward, I will update the community. Than you again DanT!!!
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When using the JB Weld (not JB Kwik), the thickness of the glue is not an issue. Fore the thickest shim, the 0.032" "pre-travel" shim, I used vice grips to throughly squeeze out as much glue as possible. This is exceptionally stout stuff, so it is not going anywhere with even a very thin film of glue. Squeezing out the glue as much as possible helps maintain the thickness. However, if that is not done, filing down the shim sets things right.
The most important thing is to make sure both the shim and the surface get "wetted" with the glue. I rub the glue into each side with a toothpick to make sure both surfaces are really "wetted" before I clamp things together.
Also, in order to get the maximum gain out of the rear "pre-travel" shims, the post under the safety should be filed down so that the safety clears with the rear shim in place. See earlier in the chain to see which post to file down for the safety to clear.
I am glad it worked out. It has been a great improvement to my trigger I know.
- DanT Phoenix, AZ
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Dan T, this forum has been tremendously helpful. You are a pioneer of scorpion triggers man. I've gone with 016 pre travel and over travel shim and it made such a massive difference. I decided to play with the disconnector (reset) and found that about 023 was needed to get a good bite on all sears. Again, what an amazing difference. I used loctite metal/concrete epoxy because of the 3200psi strength and so far it's holding tight after several hundred rounds. Thank you for sharing this information!
Sent from my SM-N920V using Tapatalk
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So I'm cheap and have a dremel tool and some calipers, so I cut apart a federal 308 case I found at the range. The neck measured .015 and the base .035. I haven't tried them in the cz yet, but with a little jbweld under them they might be pretty close to perfect. And who knows, someone might find another case that works better.
(http://i67.tinypic.com/1zvd742.jpg)
(http://i66.tinypic.com/25spgn9.jpg)
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I have noticed that my local Ace Hardware is carrying the K&S engineering brass stock much cheaper than what I got off of Amazon. A 12 inch strip is roughly $1 to $2.
The 0.016" stock is hard to cut with scissors, but it can be done. It then needs to be tapped flat with a hammer. The thicker stuff is harder to cut, but a lot of folks have access to a dremel tool with a cut off wheel.
Stealing the brass from a used shell casing certainly represents the "DIY" spirit!
- DanT Phoenix, AZ
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So I'm cheap and have a dremel tool and some calipers, so I cut apart a federal 308 case I found at the range.
You and I think alike! I did the EXACT same thing last week! I have yet to JB Weld them on yet, as I had my first USPSA match with the gun and wanted to make sure it was running like a top. Have to get it cleaned up and welded in!
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I might have to try some .40 brass I picked up but don't reload.
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I jb welded in my trigger shims I cut from the 308 case yesterday and assembled today. What an improvement! Not perfect, but good enough. The disconnector shim was perfect. The thicker pretravel shim could have stood to be a little thicker as I still have some creep, and I did have to file the back of the sear housing down to clear the safety. Thanks to Dan T for posting all his guidance. if you can afford it, get the czcustom trigger, for the rest of us, shims for the win! I went from the worse trigger have have ever felt to a trigger that feels a little better than a good polished AR milspec trigger with the set screw in place to take out some of the creep.
couple thoughts:
1- when filing down the sear for the safety, don't forget the shimmed sear will be at an angle, not flat, so you should file at a but of a rearward sloping angle if you are filing on a flat surface.
2-my narrower HBI trigger return spring was sliding off to the drivers side of the bent tip of the firing pin disconnect and dragging on the side of the trigger pack. So once again I busted out the cutting wheel on the dremel and cut a small notch in the leg where the spring will now ride instead of wandering off to the side. That sounds a little confusing to me, so I'm attaching a picture. The yellow line was where my spring leg had wandered off to, and the red line denotes where I notched on the underside of my metal finger thing to keep the spring in that location. It works great so far. (not my trigger pack, borrowed image from google and tweaked with ms paint)
(https://image.ibb.co/c5CO5Q/pack.jpg) (https://ibb.co/nscZC5)
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The geometry of the disconnector and the trigger is such that I really could not go any farther than a 0.032" "pre-travel" adjustment.
The problem is that there is a minimum disconnector "bite" needed in order to avoid un-intentional double and triple shots at the range.
(http://i38.photobucket.com/albums/e108/JWLazer/Reset%20clearance%20%202_zpsvokpwfyi.jpg)
This is not a very good picture, but with the over travel shim in place, the disconnector needs to be able to grab about half the rear hammer shelf as shown. Now if the disconnector is biting this much of the rear hammer shelf, it is going to need some "forward trigger travel" to let go. The amount of trigger travel required to "left go" is about how much travel you have left over with a 0.032" shim.
In other words, if you were to add more than 0.032" of pre-travel shim, you would have to reduce the disconnector "bite" on the rear hammer shelf and that in turn would left to a much higher chance of accidental double and triple shots.
I think there was another 0.007" of pre-travel before the trigger fires. One further point: Even if you could increase the pre-travel shim more than 0.032", you are making it harder and harder on the safety to stop the rifle from firing as you shrink the distance between pre-travel and firing to be closer and closer together.
However, at least for me that was not really even an option. I don't want doubles and triples. You do get strange looks at the range when that happens. With 0.032" pre-travel and 0.013" over-travel removed, the trigger feels way better than it did before as you have removed 0.045" (0.032" + 0.013") out of ~ 0.052" (0.032 pre-travel + 0.013" over-travel + 0.007 distance-to fire remaining) possible.
The impossibly long trigger pull has now become very reasonable. Even just doing 0.016" pre-travel and 0.013" over travel helps a lot and has the advantage of perhaps no change to the safety.
- DanT Phoenix, AZ
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Thanks for the write up DanT. I couldn't source brass shim stock locally. I bought some cheap feeler gauges and cut them up. Works perfectly!
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DanT, just wanted to post a quick thank you here. After reading your posts about your shims a few times, I went ahead and gave it a try. It worked as I'd hoped so I removed the shims and added some metal with a mig welder and filed everything to fit. Had it out to the range today and I'm still smiling. Right at 4lbs with about 1/8" of total travel. Turned out better than I'd hoped for, thank you sir!
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I am glad that it is working well for everyone. I have done a couple of these triggers, all with good improvements.
The trigger cannot be made "hair trigger" because the disconnect has to have a "half rear hammer shelf bite", and the trigger must be able to move forward just enough to undo this bite. However, that is a lot less movement than before the fix.
I also like a softer trigger pull. Polishing the trigger parts also allows for a softer trigger spring that is still reliable for the trigger reset. I run with about a 3 lbs trigger pull using a custom trigger spring. As I have said, these springs are dead simple to make and play with. 0.039" music wire is pretty cheap on Amazon.
- DanT Phoenix, AZ
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I followed these instructions, more or less, and glued in a .016" thick brass shim fore and aft of the trigger opening.
The brass was found at a local ACE hardware in their sheetmetal section. I had to buy a 1" x 36" section, because that was what they had in that thickness. I paid around #3, IIRC. I really only needed about an inch of the material to do the 3 trigger housing I have.
Using a Dremel, I cut the brass into strips that would fit fore/aft of the trigger cutout. Precision was not really necessary. I did sand the burrs off to allow the shim to lay flat.
Again, because it's what they had, I used Loctite's Epoxy Weld to glue the shims in place.
I dropped the trigger housing upside down on a 1"x2" bit of wood (protected from the glue with painter's tape) and clamped in a vise for a hour.
After an hour, they came out of the vise and was able to trim excess epoxy from the trigger opening (or anywhere else that it squeezed out) with a razor knife, then let sit for 24hrs.
Some work with a file was necessary to remove excess epoxy and slightly slipped shim from the trigger openings and 1 trigger housing's rearward (pre-travel) shim had to be filed to allow the safety to engage.
The work probably took no longer than what was needed to write this post. Obviously, I'm discounting the epoxy's drying time.
The results are very good. The total trigger travel has been reduced to about 1/8" as measured at the bottom leading edge of the stock trigger. Takeup, overtravel, and reset are drastically reduced.
With this simple mod, HBi springs, and a light polish, my trigger measures 4lbs, 7oz on average.
It's not in the same class as a Hyperfire or Geissele, but it is light years better than how it started.
I test fired it on Friday and had no problems. May shoot it in a couple of 3-gun stages on Sunday.
Thanks for the Tutoria, DanT.
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this looks really interesting DanT :) will definitely try out your mod tip one of these days. thanks brother