This report covers:

  • Specificity
  • Edge-latched
  • The point
  • Crossbow trigger
  • Ball-bearing trigger — a different arrangement
  • Summary

I had a question about triggers from reader Roamin Greco yesterday. Here is what he asked.

For some reason, I have been seeing a few of these 45s offered on ebay lately. I ended up with a Diana 35 (Actually a Winchester 435) with two adjustment screws in front of the trigger. How are the 35 and the 45 different, and how are they similar? As I commented before, I fear mine has a broken spring.”

And here is my answer to him, Roamin, They are as un-alike as two airgun triggers can be. This one is modular. Yours is pieces held together by an outer assembly shell — the spring tube. The only similarity is both of them release the piston.

Today I will explore that with you. It’s been a while since we discussed airgun triggers, so this should be interesting.

Specificity

To have this discussion we need to be specific. I will therefore address the triggers in spring-piston airguns — and, yes, SPRING piston means both coiled steel spring and gas spring. They are both spring-piston guns.

Most airgun triggers work by restraining the piston at the rearward limit of its travel, where the spring, whether coiled steel or pressurized gas, is at its most compressed state and the piston has the longest way to travel. Actually Roamin Greco asked about the difference between the Diana 45 trigger in the airgun I reviewed yesterday and the trigger in his Diana 35 that’s labeled a Winchester 435. I will start with the type of trigger that goes in most spring-piston rifles.

The pistons in spring guns are latched or “caught” by their sears ways that dictate what types of triggers will work with them. Until you understand the differences in piston types, you can’t appreciate why certain triggers such as the Rekord won’t work with certain types of pistons.

A center-latched piston has a rod in its center that in some way gets latched or “caught” by the sear. When it’s latched, the sear restrains the full force of the mainspring. That can be well over 100 lbs. of force in the case of a coiled steel spring, or several hundred psi of gas pressure in the 2-piece expanding cylinder of a gas spring. The sear prevents the piston from moving until it’s released by the action of the trigger.

center-latched piston
The center-latched piston grabs the sear with its central piston rod.

center-latched piston
A BSA Meteor piston with a center-latched piston rod (arrow).

Don’t think that the piston has to stay in the same orientation for the central latch to work. The piston in a TX200 Mark III is free to rotate on its longitudinal axis, yet still latches on the center of the piston rod.

center-latched TX200 piston
The piston in a TX200 Mark III latches on the center rod but is free to rotate around its long axis.

Edge-latched

An edge-latched piston latches on the piston’s edge. Well — duh! It just means the surface of the piston that catches the sear is located on the edge of the piston’s skirt and there may not even be a central rod. There can be, but it isn’t used for cocking the airgun. Do I really need to show a picture?

The point

The point of this discussion is that guns with pistons like this have triggers that interact with the pistons in specific ways. And most airguns have triggers that do it this way. For example the trigger of the Diana 45 is one that does.

Diana 45 trigger assembly
This is the Diana 45 trigger assembly out of the rifle. The tubular part on top aligns the assembly when it’s inside the spring tube and the two holes on that tubular part are for the two crosspins that hold the trigger assembly in the spring tube against the pressure of the mainspring.

Crossbow trigger

The crossbow of legend — not the ones being sold today, but ones made in the 14th or 15th century, had a trigger made of steel and horn that restrained a force of several hundreds of pounds — sometimes as much as 700 pounds! The bows were made of steel or of laminated animal horn and were extremely stiff. On these powerful crossbows that are often called warbows the archers used winches to draw the bowstring back to the sear that held it.

Diana 45 crossbow trigger
From Sir Ralph Payne-Gallwey’s famous crossbow book, this illustration of the trigger nut that is the sear illustrates how a vintage crossbow trigger works. That nut is made from animal horn, and the trigger from iron.

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Ball-bearing trigger — a different arrangement

Now we come to the trigger that’s in Roamin Greco’s Diana 35. I call it a ball-bearing trigger because ball bearings are what hold the piston — though they need other parts in order to do so.

Diana 35 ball bearing trigger

Diana 35 ball bearing trigger parts
These are the principal parts of the Diana ball-bearing trigger. The balls fit inside the black tube through slanted holes, one of which is shown to the left of the long slot. The small spring below fits in that slot and also presses against an edge of the large silver tube at the top left when the black tube sits inside. When the rifle is cocked the piston rod comes back and goes through the center of the black tube, pushing the three balls up out of its way. The dimples seen in the silver tube are ramps that allow the balls to press down on the piston rod and catch it. The trigger releases the silver tube, in turn acting on the ball bearings to release the piston rod to spring forward under tension of the mainspring.

Summary

Whew! I wrote all that in almost four hours of study and reflection. I wrote it just to demonstrate why a trigger like a Rekord cannot be installed in every spring gun.

Then Roamin Greco told me that wasn’t really his question. I read “trigger” into the question when it wasn’t really there. Oh, well. I answered a question no one asked. Silly me.

Next week I hope to answer his actual question that he explained after most of today’s report was written. Here’s hoping I got it right this time!