CZ 452 American Trigger Tune-Up

[wildcat junkie]

Yesterday I tried the "POOR MAN'S CZ 452 TRIGGER JOB" along with the ACE #144 spring swap.

Neither came out to suit me.

On the trigger shim I had issues with getting the precise effective shim thickness. Soldering proved to be unpractical as the sear mass sapped heat too fast to allow good flow with a soldering gun. Since using a torch, even my mini butane pencil torch, would be fraught with the danger of softening the sear. I abandoned that method. I also tried epoxy, then CA but the thickness of the adhesives yielded too little/inconsistent sear engagement. Trying to file the brass shim surface to increase sear engagement ended up dislodging the shim with either adhesive.:rolleyes:

The ACE #144 spring was somewhat successful yielding a 24oz trigger pull with the nut screwed all the way back. The problem was that screwing the nut down didn't make a significant increase in trigger pull weight.

This morning I started from square one. First I went with the OEM spring length reduction as outlined in the PMTJ. I was shooting for 20mm (.788") but I ended up with a spring length of 19mm (.750").

Since I had opted to keep the tension adjusting nut on the spring, that worked out quite well. I ended up with a trigger pull of 8oz with the minimum tension setting.

 By screwing the nut all the way down, I could increase the trigger pull to 30oz.:bthumb:

EDIT: IF YOU ARE NOT FAMILIAR OR COMFORTABLE WITH THE FOLLOWING TYPE OF WORK, HAVE SOMEONE THAT IS PERFORM THIS OPERATION!

Next, I went about reducing the sear engagement the old fashioned way, using a stone to reduce the sear engagement. Having quite a bit of experience at this sort of thing, I was confident that I could accomplish the results I wanted. If I went a bit too far, the engagement could be increased by stoning the small teat that rests on the sear behind the actual engagement surface. Be aware that at no time did I make ANY contact with the actual engagement surfaces in any way.

I used the edge of a large sharpening stone with good square edges to stone the non engagement surface of the trigger to reduce the sear engagement.

 The stirrup that houses the front pin is handy for keeping the surface being reduced square with the stone. Note that the pad behind the sear engagement surface is not in contact with the stone. If you reduce this surface, you will INCREASE the sear engagment.

 This was a "try and fit" method and it took me about 3 cycles to get the engagement where I could not feel any significant creep. I can see some gap between the sear and the pad behind the engagement notch when the striker is down, but I do not have feller gauges narrow enough to insert into the small width of the opening. If anything, it is more than needed for safety. This gap represents the amount of sear engagement.

This is the relationship of the trigger/sear when the striker is cocked. Note that the sear is now resting directly on the pad behind the sear engagement surfaces.

 I monitored the reduction process by using a fine cut-off disc on my Dremel Tool to make a small nick on the (non-engagement) corner of the edge I was working on. I ended up just removing the last bit of the nick on my final passes. If you look just above the RED arrow, you can barely see the last vestige of the nick remaining. The GREEN arrow is pointing to the actual surface on the rear that engages the sear. Do not attempt to use a stone to alter this surface. (I will cover this later)

When I was done, I did the 12" drop test of the buttstock onto a well padded carpeted surface and the 30oz setting passed. When doing any drop test, make sure your action screws are torqued sufficiently and control the rifle to assure that the toe of the stock does not hit the surface. That can split your stock.The 8oz setting would only pass about 4" drop, but it wasn't so "hairy" that it would be dangerous for bench shooting.

 At the 30oz setting, the trigger "broke like glass". On the 8oz setting I could barely feel a slight amount of creep due to the light engagement, but the trigger broke immediately when I felt the movement.

I want to secure (solder) the rear action screw boss that is dovetailed into the rear tang to make R&R'ing the stock easier. That will be a project for later when I pillar/bed the action. Torx head action screws with a torque measuring screwdriver will make adjusting the trigger before and after a bench session practical and bedding pressure consistent.

On another note; My Weaver Classic V-24 is on a UPS truck in NY State and should be here tomorrow.:D It won't be long now!:snipersmi

Trigger tuning part deux in next post.

[wildcat junkie]

Trigger tuning part deux.

In some earlier posts a few folks mentioned using a stone on the sear engagement surfaces. Working on these surfaces is a whole nuther ball of wax. It requires a different type of stone and a different set of talents and mindset.

After those posts aroused my curiosity, and I had the trigger apart for pictures anyway,  I rummaged around in my tool drawer and found one of my sear stones from my muzzleloader and revolver shooting days. I used to have 2 different stones, the triangle type pictured below and a blade type which I seldom used. The last time I used this stone was when I did a trigger job on my Remington 591M 5mm CF conversion.

I made a few very light passes on the sear engagement surface of the trigger pointed out by the green arrow in the picture below.
 

This put the finishing touch on my trigger job. It actually raised the pull weight by a few oz, but now the 10oz pull breaks like glass and it will pass a pretty significant bump test.