I had a bunch of photos to go along with this but photobucket was being difficult. After 3 uploads, I was ready to claw my eyes out. I still felt that this would be a worthwhile thread.
I picked up a CZ455 in 17hmr a couple of months ago. I took it to the range 3 times before it got to go gopher shooting on Monday. I thought the results of the trips to the range would be interesting to other cz owners .
The first day was for break-in and sight-in purposes.
The trigger was the worst that I've experienced on any BRNO or CZ that I've owned. The weight of pull seemed ok, but the creep was terrible. It only took a few shots to decide that the trigger needed to be adjusted or replaced. Anyway, I got it sighted in, so I'd accomplished what I set out to do.
Second trip was a warm Feb day of about 10 degrees and just a bit of wind. I had planned on doing the trigger work prior to going to the range, but other responsibilities got in the way. So I figured that "in the name of science", I could turn this into a before and after comparison of this cz's trigger. I fired nine 5-shot groups and recorded the results. I did this at both 50 and 100yds.
50yd results
Largest group 0.76 in
Smallest group 0.52 in
Average of the nine groups 0.65 in
100 yd results
Largest group 1.55 in
Smallest group 0.98 in
Average of the nine groups 1.29 in
Some 50yd groups from the initial trial. The two on the left were the worst of the bunch. The two on the right can't quite cover the groups. Ignore the patched target ...... it's just my frugality showing.
I can't emphasize how much creep the trigger had. I'd squeeze the trigger and I could feel the metal sliding against metal. It was difficult to tell when the trigger was actually going to break . I had no doubt that the excessive creep was adversely affecting the rifle's performance.
When I got it home, I measured the trigger pull at just a hair over 2lb. I was actually pretty happy about that as it matches the pull on the 452 that I use as my goto 22LR gopher getter. Digging through a box of spare parts, I was able to cobble together a complete YoDave kit and a couple other springs.
Note - my shim experiment may not yield the same results with your rifle. What is safe in my rifle may not be safe in yours.
I started with the red shim. It did not pass the bump test.
Next was the black shim. It passed the bump test, but I did not like the feel for a gun that was going to be carried in the field. If I was going to shoot this gun from a bench, I might have went with this shim.
The green shim gave the trigger a feel that I thought would just right for my purposes.
I tried the blue shim just for giggles. I could feel some creep but not near as much as originally.
With the green shim and the factory spring, the trigger now breaks at a nice, crisp 2lb. So it was back to the range for testing.
Here are the results with the adjusted trigger. Same lot of ammo. Similar weather. Nine 5-shot groups at both 50 and 100yds.
50yd results
Largest group 0.61 in
Smallest group 0.35 in
Average of the 9 groups 0.45 in
100 yd results
Largest group 1.23 in
Smallest group 0.85 in
Average of the 9 groups 1.07 in
This is one of the 50 yd targets that I shot. The other has 5 groups and 2 holes that can't be hidden. I like this one better.
Same target, buck naked.
I was expecting to see an improvement in group size, but I have to admit that I was surprised at the amount of improvement just from tuning the trigger. But given how poor this trigger was from the factory, maybe I shouldn't have been surprised. A lot of shooters use a YoDave kit to improve the CZ trigger. It's pretty easy to do and usually worth the effort.
Overall, I'm pretty happy with the gun. When gopher season is over, I'll try a few other things to see if I can improve the group size some more.
Again, sorry about the lack of pics. Photobucket has been miserable.