Diana's "ball-sear" trigger was used on the post-war models 25D, 27, 27S, 35, 35S, and 50, from the early 1950's well up into the 80's. The trigger is ingeniously simple, but unique.
This parts diagram is the model 25D, the smallest member of this family. I've referenced these part numbers below (but the part names are just my inventions!).
HOW IT WORKS
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 three infamous ball bearings (18) sit in holes in this sleeve, which are sized so the balls can move inward and outward a small amount. The spring guide (15) rests on the front of the inner sleeve.
2. The outer trigger sleeve (16) is the heart of the system. It moves backward when the gun is cocked, and flies forward a short distance when the gun is fired. The firing spring (21) which drives this motion is trapped between the two sleeves.
3. The outer sleeve has three recesses arranged around its center. These have two functions:
+ pushing the ball bearings inward when cocking
+ halting the sleeve's forward motion after firing (they strike the rear of the spring guide)
4. The outer sleeve also has a cut-out underneath, engaged by the two spurs on top of the sear (23/2). This is the interaction you feel when pulling the trigger (contrary to what some famous writers have said - the ball bearings have nothing to do with it!).
5. Several things happen when cocking the action:
+ The mainspring is compressed
+ The rear of the piston contacts the outer sleeve and pushes it backwards
+ The firing spring is compressed
+ The outer sleeve's recesses contact the ball bearings and push them inward
+ The annular groove around the piston stem comes into line with the ball bearings
6. When the sear engages the outer sleeve's underside recess, all this is locked into place, with the ball bearings in their innermost position, restraining the piston. When you pull the trigger, the firing spring pops the outer sleeve forward, the ball bearings are shoved outward, and the piston is released.
STRIPPING THE TRIGGER
+ The inner parts come out with no need to remove the trigger blade
+ The mainspring is under some tension when the trigger mechanism is in place. A spring compressor is absolutely required to keep things under control
+ Go slowly with the compressor. Put a rag around the back of the receiver as things come out, to catch any wayward bits
+ To disassemble: pull off the sheet metal rear cap; put the gun in the compressor with a little tension on the protruding inner sleeve; drift out the retaining pins; hold the trigger back. Now unwind the compressor and the whole mechanism will follow
+ To re-assemble: "glue" the ball bearings to the inner sleeve with grease; stack both sleeves on the spring guide; drop this assembly into the mainspring; hold the trigger back. Now snug up the compressor
+ Its easiest to insert the firing spring after the sleeves are partially pushed past the rear of the receiver, which will help to restrain it
+ When re-inserting the cross pins, use a slave pin (a punch or similar) to align the sleeves. It usually takes a bit of patient wiggling around
ADJUSTING THE TRIGGER
+ IMPORTANT: the total length of the trigger pull, and the actual pull weight, are fixed! Only the transition point between the first and second stages is adjustable
+ The rear trigger screw (part 23/8) is the actual adjuster. The front screw (23/7) is a lock to keep the adjuster screw from turning
+ The end of the adjuster screw strikes the bottom of the receiver tube when the trigger is pulled. This forms the fulcrum for the second stage of the pull
+ To adjust the trigger, loosen the lock screw, adjust as needed, then re-tighten the lock
+ Turn the adjuster screw in (clockwise) for a longer second stage, or out for a shorter one; work slowly in quarter-turn increments
RANDOM NOTES
+ It is possible to grossly mis-adjust this design. If the adjuster screw is too far out, the pull is "all first stage" (a light spongy pull, with no feel for the letoff point). Too far in, it's "all second stage" (a stiff gritty pull that is similarly unpredictable). In other words...when you get that second stage short and crisp - stop!
+ The models 25D and 27 have the trigger as shown. On the models 35 and 50, the same trigger parts are used, but have more room to wiggle around inside the bigger-diameter receiver, so the firing spring adds its own little spring guide.
+ Up to about 1964, these guns had lovely solid alloy triggers; then plastic ones up to the early 70's; finally the stamped steel blades that are most commonly found. The adjustments all work the same with one odd exception: the plastic trigger omits the adjustment lock screw. The friction of the long adjuster screw against the plastic is sufficient to keep it from drifting. (Pic is three model 27's.)
Very well illustrated in both words and photos!
Is this trigger setup the immediate predecessor to Diana's 'falling block' trigger?
Thanks
I don't know what a "falling block" trigger is...
Me neither to be honest. I recall a previously owned early '80's (late 70's production?) Diana model 45 that IIRC touted the trigger of that model as having a falling block design. After fully reading your post, it got me scratching my head a little in trying to connect the historical dots, as it were.
"Modern" may be relative is all. Could be the 45's trigger was exclusive to that model. I'm clueless though I liked that gun.
The newest Diana (54) that I'm familiar with is over 30 years old and a relative now has that one. Never fooled with the trigger much on it.
Thanks
Thanks! I don't know details of how the model 45's trigger worked, but I do know it is unique. It's quite different from the previous ball-sear design, or the triggers used in the new generation beginning about 1985. The only other gun to have this trigger was the model 50 T01 underlever, which used the 45's powerplant.
The so-called "T01" trigger in the early model 34, etc. is a ball-sear mechanism that fits in a removable module, and with a safety added. AFAIK it shares no parts with the classic early ball-sear though. The later T05, T06, etc. triggers go in another direction.
BTW the "T" numbers do not refer exclusively to triggers. It stands for the German word "Typ" ("type" or "model"), and can refer to any significant change in a gun's design. The 50 T01 underlever noted above is an example; the earlier model 50 was quite different, based on the model 35 barrel-cocker.
Mike, I have seen that explanation on the ball trigger before and am not so sure about the front screw being only a lock screw as Tom Gaylord also said. I have played with a few of them. Screwing all the way in won’t hurt, but I didn’t like the trigger weight of it then. My take was that the front screw is a first fulcrum point and then screw 2 gets involved. I’ve only gotten a nice trigger with the front screw not all the way in.
My adjustment takes a fair bit of cocking and decocking trial and error. On my notes, I cautioned myself, that the front screw is only adjusted out AT MOST 1/4 turn. It is a balancing act between crispness and trigger weight. Rear out too much is mushy and in too much gives heavier feel. Rear out too much and gun won’t fire. Front out too much and danger of sear not catching or firing by itself perhaps. With lots of playing around a balance is reached. Err to the side of safety.
Once adjusted, one can check this by turning in front screw to lock and noting how it just messed up your nicely adjusted trigger.
Edit: this is mostly for the T01 safety style ball trigger guns, but my 27 is adjusted the same
The old Diana ball-sear and newer so-called "T01" triggers work on the same basic "three ball" principle, but the T01 is much more complex, being "modularized" and adding a safety. The T01 is a bit outside my realm but covered nicely elsewhere on the net; I'd be cautious in assuming its adjustments work precisely the same as older guns.
On the ball-sear the lock screw is just a lock screw. For early examples with the solid metal trigger blade, it directly contacts the long adjuster screw to keep it from turning, simple and direct.
On the final ball-sear generation with stamped trigger blade, the lock screw works in a more roundabout way (photo is a late model 27). As you can see, both trigger screws pass through a stout bent tab of metal. Tightening the lock screw apparently bends that tab just enough to bind the threads on the adjuster screw.
As you can see, the lock screw does not contact any other surface beyond the trigger blade itself, so can't act as any sort of fulcrum. Possibly leaving it very tight or loose might cause some odd effects, but I've got 10 ball-sear rifles and find the adjustments consistently straightforward.
I confess to comparative total ignorance of more modern Dianas! I don't know what a "falling block" trigger is... 🤔
Not to hijack your post, Mike, but the "Falling Block" trigger of the 45 is about the same as the T06 NTec trigger, that is now in the 34 EMS model.
What retains the piston in place when cocked is not a button at the end of a stem hooking into a retainer (whether three balls, two plates or a hook), it is a slot in the piston's skirt that is held by a ramp.
As such, the whole weight of the mainspring acts on the ramp (or block), and when the sear allows it, the block drops "muy rápido".
Which makes for a fine and fast trigger.
Now, back to the regular programming, we apologize for the inconveniences caused.
😉
HM
Merry Christmas!
To me the simplest explanation is that a ball sear works similarly to an air chuck. When you pull the sleeve back it releases the probe on your air tool. I don’t know if the air chuck or ball sear trigger came first but I have to wonder if one inspired the other.
David Enoch
Pics lurking in the archives...should have included with my initial post!
Top to bottom: cross pins, ball bearings, inner sleeve, firing spring, outer sleeve, spring guide. You're looking at the top of the inner sleeve (note slot for the firing spring, and one ball bearing resting in place); and the bottom of the outer sleeve (big angled notch at the rear is where the trigger sear engages).
Another shot of the guts, spring guide in place on the inner sleeve. The gun is a "Winchester 427" (Diana 27...with a broken plastic trigger blade! ☹️ ).
Three generations of the ball-sear trigger blade: early solid aluminum; plastic; final stamped metal. Again, all model 27's.
