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  #1  
Old 01-10-2017, 11:07 AM
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452 American Trigger Tuning



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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.

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.


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 pad 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 engagement.



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. It won't be long now!

Trigger tuning part deux in post #18

Last edited by Wildcat Junkie; 07-02-2017 at 12:10 PM.
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  #2  
Old 01-10-2017, 11:19 AM
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Nice post WC. Man you're really getting that thing dialed in. Weaver Wednesday for you eh? Sweet!
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Old 01-10-2017, 03:49 PM
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12" drop test on to the butt of the stock is a bad idea. That can chip wood around the tang or worse yet split a stock. Rubber mallet to the rear of the tang while the action is still out of the stock. Hate to see you break your stock. It is your rifle to do as you want.
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Old 01-10-2017, 04:04 PM
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Nice work, do you have pictures of the process?
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Old 01-10-2017, 05:07 PM
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Originally Posted by Howes View Post
Nice work, do you have pictures of the process?
No, I didn't take any pictures When I dismantle it to do the pillars and bedding, I'll take a picture of the relationship of the trigger to the stone.

In the mean time perhaps I can describe the relationship with the picture below.



If you look closely you can see the top edge of the sear engagement notch. It is perpendicular to a line that extends from it to the front edge of the stirrup that the front pin is peened into. My stone is very large. It was originally housed in a commercial meat cutters sharpening fixture.

If your stone is small, secure it to a block where the edge of the stone is even with the block. You want a 90*edge long enough to rest the stirrup against to maintain a consistent angle. Then you can draw the trigger across the stone to reduce the surface. You must go slow and check your work as you go. A small nick, perhaps -005 - .010" deep in the front edge will allow you to monitor progress. A nick on each side of the front edge near the sides will allow you to assure that you are keeping the surface square in the side to side axis.

Last edited by Wildcat Junkie; 07-04-2017 at 11:34 AM.
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Old 01-10-2017, 05:14 PM
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Quote:
Originally Posted by bandit1250 View Post
12" drop test on to the butt of the stock is a bad idea. That can chip wood around the tang or worse yet split a stock. Rubber mallet to the rear of the tang while the action is still out of the stock. Hate to see you break your stock. It is your rifle to do as you want.
This is done carefully and the action screws are torqued sufficiently. Bear in mind that this is a carpeted surface with ample cushion and the rifle is not left to fall without control. Yes, if the stock were to land on the toe, it could split it.

In my experience, triggers will act differently once the action is torqued down into the stock. This not only applies to the sear jarring loose, but to the actual trigger pull weight.
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Old 01-10-2017, 07:39 PM
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Quote:
Originally Posted by Wildcat Junkie View Post
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.
I put a shim under one and that works fine, but this morning on another 452 I went with a real "quick and dirty" - I cleaned both parts then coated them with a little Permatex Gasket Seal.

It doesn't need to be able withstand hammer blows, you just don't want it to fall out every time you take the stock off and tilt the barrel over!

Great guide on the trigger. I shortened my spring to where I am at about 19 oz, a good compromise for both bench and hunting. It has a wee bit of creep in it which I was going to remove the same way you did, but you know, after shooting it a while I have grown kind of fond of it. It is very consistent, and I'm getting to where I like knowing exactly when the trigger is going to break. My old, numb fingers don't gauge pressure that well but I can detect that creep!
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Old 01-10-2017, 09:39 PM
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Wildcat Junkie,

Thanks for the detailed write-up! I'm sure some folks will find the data you reported to be useful.

JMK
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Old 01-11-2017, 12:22 AM
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Timney will allow you to do all that with a simple turn of an allen wrench.
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Old 01-11-2017, 06:08 AM
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Yeah but it's nice to be able to achieve a great trigger without spending one cent.

If I might want to change the pull-weight in the future I get a Rifle Basix replacement, but if I don't plan on ever changing it tweaking the 452 trigger suits me just fine.
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Old 01-11-2017, 06:38 AM
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Quote:
Originally Posted by Big-Dummy View Post
Timney will allow you to do all that with a simple turn of an allen wrench.
And the shelling out of a $100 bill. And BTW, in addition to the Allen wrench, you also need a wrench to loosen and tighten the jam nut on the Timney.

Quote:
Originally Posted by SavagePlinker View Post
Yeah but it's nice to be able to achieve a great trigger without spending one cent.

If I might want to change the pull-weight in the future I get a Rifle Basix replacement, but if I don't plan on ever changing it tweaking the 452 trigger suits me just fine.
While I use Timney triggers on all of my custom Mauser prohects, in this case it didn't allow the low trigger weight that this modification does. By keeping the adjusment nut on the spring, I can adjust my trigger pull from 8oz to just under 2# (30oz) with a simple turn of a 1/4" open end wrench.


One of my pet peeves with the Timney triggers on my Mausers is that it is hard to maintain a given adjustment when the lock nut it tightened. This is especially difficult with sear engagement and over-travel.

Last edited by Wildcat Junkie; 01-11-2017 at 06:41 AM.
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Old 01-11-2017, 06:39 AM
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I don't recommend reducing dear engagement.
In fact it is the wrong way to do it!

The correct way is to use a stone, not to reduce sear engagement but to adjust the angles of engagement. This then aids them sliding away from each other.
Many triggers today are actually designed to induce a camming action against the hammer or striker spring via the angles of the sears.
I heartily do not recommend reducing sear contact.
I have been working on triggers for over thirty years now.

R.
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  #13  
Old 01-11-2017, 06:54 AM
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Quote:
Originally Posted by Ratdog View Post
I don't recommend reducing dear engagement.
In fact it is the wrong way to do it!

The correct way is to use a stone, not to reduce sear engagement but to adjust the angles of engagement. This then aids them sliding away from each other.
Many triggers today are actually designed to induce a camming action against the hammer or striker spring via the angles of the sears.
I heartily do not recommend reducing sear contact.
I have been working on triggers for over thirty years now.

R.
Reducing the sear engagement the way I did it is no different than the way any of the myriad of adjustable triggers on the market or the Yo Dave mod achieve the same thing. It is just not adjustable.

While I agree that changing the angles will reduce pull weight and smoothness, it doesn't reduce creep.

Changing the angles has it's own potential hazard as it can make the trigger more prone to being jarred loose. While I have done so myself, I would heartily recommend that a novice not touch the sear surfaces themselves.

I've been doing this on revolvers and muzzleloaders for over 30 tears too.

Last edited by Wildcat Junkie; 01-11-2017 at 06:59 AM.
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Old 01-11-2017, 07:29 AM
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Quote:
Originally Posted by Wildcat Junkie View Post
Reducing the sear engagement the way I did it is no different than the way any of the myriad of adjustable triggers on the market or the Yo Dave mod achieve the same thing. It is just not adjustable.

While I agree that changing the angles will reduce pull weight and smoothness, it doesn't reduce creep.

Changing the angles has it's own potential hazard as it can make the trigger more prone to being jarred loose. While I have done so myself, I would heartily recommend that a novice not touch the sear surfaces themselves.

I've been doing this on revolvers and muzzleloaders for over 30 tears too.
Thank you for your kind response.

R.
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Old 01-11-2017, 07:47 AM
200yd
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OP, is there shim stock on the sear in your photo?

This does not directly relate to the original post, but does anyone know if the sear and trigger engagement faces are case hardened? Do you run the risk of cutting through the hardened layer if you try to clean up the surfaces?

There doesn't appear to be any sear engagement in your photo, is that correct?

Could you add some arrows to the photo? I'm sorry but I'm not tracking.

Last edited by 200yd; 01-11-2017 at 07:56 AM.
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