CZ Scorpion EVO Trigger Job - reducing trigger pull/reset length

[Rick53]

That right rear shelf can be filed down. In fact, this is common practice for those of us who bought the CZC trigger pack and had to fit it. You can get rid of some more travel. 

I hate to remove metal in the name of experimentation.  It is too costly to replace a part (like the hammer) when (not if) I remove a bit too much metal.  Filing the rear hammer shelf has the same effect as placing a shim under the disconnector foot.  Both vary how much "bite" the disconnector hook gets on the rear hammer shelf.

Music wire has very tight tolerances, is very cheap, is available in 0.002" increments and is quite tough.  I have also considered using that stuff for these shims.  A straight piece for the rear trigger feet, and an "L" shaped piece for the disconnector foot (a section in line with the foot, then bent towards the middle to get it where it can be tacked down), both tacked in place with a toothpick drop or two of quick set epoxy.

When I started experimenting with the trigger/disconnector spacing, I first started with folded typing paper.  This is not really very good for the range, so I then graduated to folded up kitchen aluminum foil, which is incredibly thin (~ 0.001" per layer?).  That worked pretty well for quick prototyping and proof-of-concept, but is not very reproducible for other folks.  However, when I was happy with the results, I could measure the thickness with my calipers and see where I was at.  At that point I started looking around for a commercially available material with the right thickness.  After some searching I found 0.016" thick brass strips. Cheap. Available. Easy to work. Readily reproducible.

In my tests I did push the reset to a much shorter length.  I recall that this was in the area of 0.020".  Since I was already using 0.016" for the trigger shim, I figured that 0.016" was "good enough"(but not optimum) for the disconnector foot shim as well.  I might order a spool of 0.018", 0.020" and 0.022" music wire to use as potential disconnector spacers and see which provides the shortest trigger reset with some margin. That might provide a reproducible solution for others to work with.  Alternatively I just might get some "heavy duty" kitchen aluminum foil and fold up just what I need for my own personal use for the disconnector shim.

I have pulled this trigger apart so many times I think I could re-assemble it in my sleep.   With a bit of love and care, it seems to be a pretty nice trigger.  Not CZ 75 SP-01 Accu-Shadow nice , but nice none-the-less.

I saw a video of the CZ Custom Shop demonstration of their CZ EVO trigger at the 2017 SHOT show.  The reset distance using the stock disconnector was really, really short.  I don't think I would push it quite that close.

It was fun endlessly playing with the trigger mechanism as I kept getting better and better results.  Every once in a while everything would lock up because one of the roll pins (either trigger or hammer) had worked itself out of its hole one on one side or another.  I had to constantly keep pushing these pins back into place.

- DanT  Phoenix, Az

To BAD YOU DIDN'T TAKE PICTURES : tHEY CAN SPEAK 1000 WORDS

[dlidster]

DanT,

Nice thread you've started with clear documentation. I look forward to photographic support.

Veritable cults have arisen supporting the fine-tuning of triggers for the Ruger 10/22 (I have seven) and the  CZ 75 (I have three) with thoughtful workmanship and a minimal financial investment in parts. I believe the same is going to happen in support of the Scorpion EVO trigger. Thanks for contributing.

BTW, while the trigger pull should be lightened and smoothed, my own priority would be in reducing reset. I'm interested in the Scorpion EVO carbine as a PCC in steel matches and IDPA/USPSA. For action shooting a quick, positive reset is everything.

[DanT]

To BAD YOU DIDN'T TAKE PICTURES : tHEY CAN SPEAK 1000 WORDS
[/quote]

I have pictures.  I just don't know how to get them posted here.  It appears like I need to put them somewhere on the internet and place the link here.  I just have no idea where to put them.

- DanT  Phoenix, Az

[Fate]

Tinypic.com is free and easy to use.

[SouthernScorp]

Tinypic.com is free and easy to use.

postimg.org  free, more storage, doesn't resize or crop images

[CaptJager]

and i was going to suggest imgur but please post pics If you have issue pm me and I will give you my email and I will send you the links to pics

[DanT]

Tinypic.com is free and easy to use.

Thanks!  I struggled a bit and managed to get a couple embedded in the earlier posts.   I didn'the quite get the size right on the first couple, but I am getting there.

- DanT  Phoenix, Az

[DanT]

I tried to "push the envelope" a bit more on the trigger reset.  I used kitchen aluminum foil to do this.  In my case, I started with a 6" strip of foil.  I look at this foil length in two parts:  One part folded in half multiple times in order to get most of the bulk thickness, and second part that is rolled up around the first bulk thickness.  This "rolled up" part is used to "fine tune" the thickness.  Why file when you can unroll and tear off?



In my case I folded in half 4 times (16x thickness), but with my foil thickness I could have started with 5 times (32x thickness) before "rolling up" the fine tune section.  Just make sure to thoroughly flatten the resulting shim before proceeding.

In any case, temporarily stuff the shim under the disconnector foot to test the trigger release distance.  I use tweezers to poke it into place.  My fat fingers don't fit down there very well.



You want to start too thick, and then get thinner.  That means unrolling the shim layers and tearing off a layer at a time.



When you get the right thickness, trim the size down and tack it down with some epoxy.



I found that 0.030" was about right for a short reset distance that I was comfortable with.  You could likely push it a bit further than that.  This is really easy to try out using an aluminum foil shim.  If you really wanted, you could use calipers to measure the resulting thickness, find some soft shim material such as aluminum or brass sheeting that is a bit too thick, and file it down to the right size.  Cheap shim material is much more forgiving of going too far (next shim please) than overdoing it on these expensive trigger parts.

I guess I could stack two of the 0.016" brass shims on top of each other (~ 0.032"), then glue or solder them together, and then file the stack down for the right shim height.

The trigger spring tends to "snap" the trigger all the way forward when the reset releases.  That somewhat defeats the purpose of a short trigger reset. Thus I might have to work on removing some metal from the top rear trigger foot near the disconnector spring.  That is the spot the safety blocks that is currently limiting me to a 0.016" trigger rise (41% take up reduction).  Bringing the top of the rear trigger foot down means I can raise the trigger foot up some more while still (just) clearing the safety allowing further reduction of the trigger pull length.

Given that the CZ custom shop has reduced the trigger length from 0.3" to 0.1". That would be the same as raising the rear foot up to ~0.026".  I really hate to remove metal though.  I would have to remove about 0.010" from the top of that foot.

I am not sure if going to 0.026" would defeat the firing pin safety or not, which is what the long lever on hammer roll pin is all about.  I don't know how to test that.  Anyone have any ideas?

- DanT  Phoenix, Az

[akuser47]

Awesome thread thanks  so much for this info. I think this will be my next project I already did the HBI springs,but I think it can be better yet.

[terry mc]

To get the short trigger reset the CZC trigger pack has a full bag of tricks.
It has shorter hooks compared to the stock sear, it has both pretravel and overtravel screws on the sear.
Additionally there are some changes on the hammer shelves as well, so there are quite a few changes to the geometry.
So the shims do address the pretravel just as with the CZC pretravel screw.

I like your thought process of reversibility, considering that the Hammer cost $99, and the Sear cost $99, and the Disconnnect cost another $99 from CZ USA, it can get very expensive to make a mistake cutting these parts.
This also makes the cost of the CZC trigger pack seam a lot more reasonable considering the cost of the parts it replaces.

One of the things that really bothered me about the stock trigger was always the spongy feel created by the drop in weight once the sear disengaged and you still had a lot of overtravel. The CZC overtravel screw is wonderful in taking care of this.

I have had 4 variations of the Scorpion trigger and would never go back to the long travel spongy mess that came on the gun. It made hitting what you are shooting at a lot more difficult. A different kind of safety concern.

Good work Dan keep working on making your gun a more precise tool.
Good to see another Phoenician on here as well, lots of Arizona CZ shooters on this forum.

[DanT]

I found I had 0.025" brass stock laying around. I could not help myself. I had to remove metal to allow the trigger travel to be shortened up even more.  Since the trigger releases at ~ 0.039" of height,  a 0.025" brass trigger shim removes about 64% of the long stock trigger travel.

In order to do that, I needed to file off about 0.011" from the top side of the rear trigger foot. There is a "divet" right in front of this foot for the disconnector spring.  0.011" takes the top of this foot almost down to the top of the divet.



The big thing about raising the rear trigger beyond 0.016" is that the trigger foot no longers clears the safety.  Thus going from 0.016" to 0.025" requires removing 0.009" ideally from the top of the trigger foot.  I had to go a bit further than that.  The main thing is to check the safety clearance as you go or when you are done.



I temporarily fit the safety back in (did I mention your never need to remove the left safety handle for disassembly?) and check for fit.  If you don't have enough clearance, the left side of the safety tends to pop up when the safety is engaged.  A tiny bit (as shown) is ok, but I started with 0.010" removed (not enough) and had to go a bit further to get the gap on the right down to this point.

So with the 0.030" disconnector shim and the 0.024" reset shim, the trigger is feeling pretty good.  Shorter pull works well with the short reset.  The trigger could be smoother.  That darn long lever on the hammer roll pin (firing pin safety) causes more drag than I would like.  I tried creating a washer out of the 0.016" brass, but it was perhaps 3x or 4x too thick.  It seems like others have been there and done that, but I had to try it out myself.

Final mods: 0.025" brass trigger shim, 0.030" aluminum foil disconnector shim, 0.011" removed from rear trigger "foot" top for safety clearance, home made trigger spring, and HBI disconnector spring:



If you want a 0.025" or 0.016" brass trigger shim to play with yourself and another small piece for the disconnector (reset length) to either use as is (0.025") or as a base to wrap in foil for a thicker 0.030"+ shim, drop me a line  and I can send something out for a few bucks for experimentation purposes.

Someone also previously commented that the "trigger slap" that I found so annoying in the stock trigger is caused by the disconnector spring.  I didn't recall changing that spring, so I kind of discounted that comment.  However when I dug out my HBI trigger spring kit, I found that I did indeed already swap out the disconnector spring using the weaker HBI disconnector spring.  If that was what solved the "trigger slap" issue, then I highly recommend it. 

I think that is about it.  I later replaced the disconnector shim with an all brass version (0.032" brass strips are available on line) which was filed down to 0.030", but that did not really change the performance.

- DanT  Phoenix, Az             email: p26412@nokia.com

[Obiwan]

I myself had used adhesive copper strips in the past. (Thin strip of copper with adhesive backing on one side. Used by Tiffany folks and other crafting hobbies. I have grounded strips on my desk to ground myself and discharge static electricity before touching electronics). But the problem with those is that gun oil will cause the adhesive not to sick.

Anyway, rather than using strips of foil and brass, and to provide for a more rugged setup, you probably could:
1) Drill and tap the bottom of trigger cage in the proper spots and use lock-tited set screws.
2) Place spot welds in those spots and file them down to proper/desired height.

I was considering spot welds around triggers themselves to eliminate pre- and over-travel. (Though not on the Evo. Seeing how easy that might be, I' may start tinkering with that).

[DanT]

Anyway, rather than using strips of foil and brass, and to provide for a more rugged setup, you probably could:
1) Drill and tap the bottom of trigger cage in the proper spots and use lock-tited set screws.
2) Place spot welds in those spots and file them down to proper/desired height.

I was considering spot welds around triggers themselves to eliminate pre- and over-travel. (Though not on the Evo. Seeing how easy that might be, I' may start tinkering with that).

Wow,  welding is hard core.  It sounds like something you are used to doing.  I guess the old saying is "to a man with a hammer, all problems look like nails". 

I have found that when I tack the shims in place with epoxy, they don't willingly come back out.  But they can and do come back out if I really want to.  As perhaps you can tell, I have changed them out a couple of times.  All brass shims would be nicer.  The trigger shim is already solid 0.025" brass, and I could use two sheets of 0.016" brass stacked (epoxied or soldered) to get the 0.030"/0.029" disconnector shim (after some filing) and drop the foil.

I do agree that there are more than one way to do this.  Each to their own expertise.

- DanT   Phoenix, AZ

[omnidj]

Beyond replacing springs (which I did), I have no desire to be an amateur gunsmith with this trigger group. That said, I would like a trigger with less travel, lighter, crisper pull and with a better reset. And I'm not a match shooter. I'd just like what I've become accustomed to with my Glock pistols. Does anyone know of a manufacturer who is developing a drop-in improved trigger for the CZ?

[DanT]

Beyond replacing springs (which I did), I have no desire to be an amateur gunsmith with this trigger group. That said, I would like a trigger with less travel, lighter, crisper pull and with a better reset. And I'm not a match shooter. I'd just like what I've become accustomed to with my Glock pistols. Does anyone know of a manufacturer who is developing a drop-in improved trigger for the CZ?

The CZ custom shop has a kit that upgrades the trigger and the hammer.  Short trigger pull length, short reset length, 4 to 5 lb trigger weight.  Looking at the picture, it appears to have changed a bit from the stock trigger.  It even has pre-travel and over-travel adjustment capabilities.

https://czcustom.com/czc-parts-made-in-the-usa/cz-evo-trigger-pack-czc.html

Here is a video demonstration of the CZ Custom Shop trigger (go to the 6 minute mark) from SHOT 2017:



Very impressive. 

That video started me down the path I have taken here. The travel in this video seems a bit shorter than what I currently have, but I am getting similar short travel/short reset behavior with two brass shims (0.025" for the trigger, 0.032" filed to ~0.030" for the disconnector) plus a small reduction in the trigger foot height for the safety. 

There is nothing magical about the EVO trigger.  It is a pretty simple mechanical device.  The more you work with it, the more you understand that.  Simple is good.

I have been to the CZ custom shop in Mesa, Az once to have my CZ 75 SP-01 Accu-Shadow sight fixed.  They do great work.  It is also very awe inspiring to browse the extensive line up of shooting competition trophies from all over the world. 

- DanT  Phoenix, Az

Later added note (3-31-2017):

This thread has been continued in:

http://www.czfirearms.us/index.php?topic=86290.0

The recommended shim sizes has been changed, a shim for over travel has been added (there is quite a bit of over travel), quick set "JB Kwik" epoxy is not good enough for gluing these shims down.  Slow curing regular "JB Weld" is much better.

- DanT