Winchester 425 Trigger ?

Wow! Looks as if someone fabricated a replacement trigger. I would recommend a bar clamp or other spring compressor device when disassembling, I did watch a guy tear down and reassemble a gun with the 3-ball sear and you will definitely need one to reassemble the gun. Does the trigger function now? Mike Driskill may know of a parts source. Have you tried any Google searches? You may find some videos or old threads that will help. Your rifle looks to be in very good condition.

Might wanna go look for a Diana 35 trigger.

https://www.pyramydair.com/blog/2012/11/diana-25-air-rifle-part-1/

https://www.pyramydair.com/blog/2012/11/diana-25-air-rifle-part-2/

https://www.pyramydair.com/blog/2012/11/diana-25-air-rifle-part-3/

https://www.pyramydair.com/blog/2012/12/diana-25-air-rifle-part-4/

https://www.gatewaytoairguns.org/GTA/index.php?topic=16085.0

https://www.gatewaytoairguns.org/GTA/index.php?topic=97160.0

https://www.gatewaytoairguns.org/GTA/index.php?topic=171986.0

https://www.gatewaytoairguns.org/GTA/index.php?topic=167206.0

https://www.tapatalk.com/groups/thedianawerkcollective/winchester-model-425-t2345.html

It definitely looks like a model 25D, with the ball-sear trigger. What is the production date (appears in "MM YY" format in tiny numbers on the left rear receiver tube)?

If the trigger works, there probably are no ball bearings rolling around inside; there are three balls, mostly fixed in one place, that work as an ingenious sort of clutch mechanism.

You DEFINITELY need a spring compressor for this one. The spring is not brutally strong, but the trigger components are not "boxed" as with, for example, the Weihrauch Rekord. It's very difficult to keep things lined up without one.

Here is the parts diagram (but, I think your trigger unit is slightly different from this one).

Neat rifle. Keep in mind two things:

1) The low power means the rifle jerks less when fired.This is a big plus. Most likely this is a pretty accurate gun. it just takes practice learning how to hold it. The poor trigger is your biggest hinderance. 

2) Our British friend live with under 12 FPS. The kill rabbits, squirrels, pigeons, rats, etc. all the time. I've watched many YouTube videos of them using sub-12 pound springers and hunting them all. None of them are long range guns but like all air rifles, accuracy is the key. 

You are quite a craftsman.

The ball bearings are buried in the mechanism, and form the "secondary sear" that grabs the piston stem (the same job as that big hook on top of the Weihrauch Rekord, if you're familiar with that). They don't touch the trigger blade. If they aren't in their proper place, I'm pretty sure the trigger would not work (though I could be wrong!...maybe 2 out of 3 might work).

I'll try to post some pics tomorrow to explain my previous notes about the variations in this trigger. 

A bit slow with my promised reply, but this interesting thread has given me a chance to play with the guns that I own and figure some things out! These pics are all of model 27's by the way, but the 25 is identical - same trigger parts, fitted into a shorter, but same diameter, receiver tube. 

Part 1...using the available newer trigger parts in your older gun.

This first pic is of a late-production gun. Note the two pins in the pic; "1" is the first-stage pivot point (part no. 23/4 in the parts diagram), which compresses a small spring (23/6) at the front of the sear (23/2). "2" is the second-stage pivot point (23/3), which compresses a much stouter spring (23/5) at the back of the sear. A nice advantage of this trigger variant is that you can remove the trigger blade (23/1) by simply drifting out the first-stage pin; no need to remove the sear.





Below is the trigger your gun probably had. The blade is plastic (and notoriously fragile, no doubt the reason yours has been replaced). It works the same way, but NOTE that the trigger bracket welded to the receiver tube is a different design, which covers up the first stage pivot. So - the good news is: yes, you can use the later style stamped metal trigger. But the bad news is: you will have to drift out both pivot pins to do it, and wrestle separately with each of the little springs.





If you buy the new trigger parts, you will also have to get the two screws shown below the trigger in the diagram. The long screw (23/8) is the adjuster, the short one (23/7) is a lock that keeps it from rotating once set. The end of the long screw strikes the underside of the receiver tube, serving as the fulcrum point that moves the trigger from first to second stage. The thing you adjust is this transition point - you cannot change the pull weight per se.

As a point of interest, this shot shows the plastic trigger, the lovely solid alloy trigger that preceded it, and the stamped blade that came later. Note that the plastic trigger omitted the locking screw - its friction against the adjuster screw did the same job.

Part 2...how the trigger works. Let's look again at the parts diagram:



1. The inner trigger sleeve (part no. 17) is fixed into position within the receiver, by the two stout cross pins in the action (19 and 20). The famous ball bearings (18) sit in holes in this sleeve. These holes are sized to permit the balls to move inward and outward a small amount. The spring guide (15) sits on the front of this sleeve.

2. The outer trigger sleeve (16) moves backward when the gun is cocked, and flies forward a short distance when the gun is fired. The firing spring (21) is trapped between the two sleeves.

3. Note the outer sleeve has three recesses arranged around its center. These have two functions: a) pushing the ball bearings inward when the sleeve moves backward; b) halting the sleeve's forward motion against the rear of the spring guide after firing.

4. The outer sleeve also has a cut-out underneath, that engages the two spurs on top of the sear (23/2). This is what you "feel" when pulling the trigger (the ball bearings have nothing to do with it).

When you cock the gun: a) the piston contacts the outer sleeve and pushes it rearward; b) the firing spring starts to compress; c) the outer sleeve recesses start to push the ball bearings inward; d) the annular groove around the piston stem moves toward the ball bearings. When the sear catches, all this is locked into place - the ball bearings in their innermost position, restraining the piston. When you pull the trigger, the firing spring pops the outer sleeve forward, and this all reverses itself in a hurry.

Hints for working on this trigger: a) use a spring compressor, and put a rag around the back of the receiver as things come out, to keep ball bearings and little springs from flying around the room; b) to start disassembly, pull off the sheet metal rear cap and put a little compression on the inner sleeve - the retaining pins should pretty much fall out; c) to start re-assembly, "glue" the ball bearings to the inner sleeve with grease, stack the sleeves on the spring guide, and then drop this mess in front of the spring compressor; d) insert the firing spring after the sleeves are partially inserted past the rear of the receiver, which will help restrain it; e) use a punch or other dummy pin to align the cross pin holes (it will take some patient wiggling around but the pins do go back in!).

Truly my pleasure! I've been meaning to figger out the various vintages of ball-sear triggers for many moons, and enjoyed having the excuse to do so.

This link from Hector is an incredible resource for Diana fans. You will find a much cleaner version of the parts diagram under "Ersatztellisten Luftgewehre." You might find it amusing to compare the 25D trigger to the bone-simple one in the basic model 25, LOL. 

https://www.diana-airguns.de/service/ersatzteillisten

One more pic. Bottom to top: a) spring guide; b) bottom side of the outer sleeve, showing the sear notch, and two ball-pusher recesses; c) firing spring; d) top side of the inner sleeve - with one of the dreaded ball bearings in place! - and the firing spring slot; e) the two cross pins.

Not positive, but that looks about right. The spring is about 9/16" long when installed in the trigger.

Here's one in place, in a model 27 (a "Winchester 427" about the same age as yours - with a broken plastic trigger!). It's stout - I can't compress it by pressing directly down on the back of the sear.

Yeah until I started looking at my guns yesterday, I'd never realized how the earlier guns cover up the first-stage pivot pin with the trigger mount bracket. On the later ones you can take the trigger blade off without removing the sear, or having to deal with the "23/5" spring.

On guns with the correct trigger, you don't have to take the trigger or sear off to get the piston out. You simply pull the trigger (to get the sear out of the way) when taking the guts in or out.

With the correct trigger, there are no side shims, it fits pretty closely into the sear.