RidgeRunner’s Diana 34.
This report covers:
- Mainspring out
- Remove the piston
- Report 1
- Report 2
- Why so smooth?
- Why cocking was hard
- What now?
Today we open up reader RidgeRunner’s Diana 34 (no, it is NOT an RWS 34 — RWS doesn’t make airguns!) and see what we find. My “Final observation” from Part 1 was partly correct. This is a practically new Diana 34. I doubt it has had 500 shots since new. But the “assumption” that the mainspring was broken was incorrect. The mainspring is whole.
I know you all want to see the disassembly so I’ll show it. First I put the barreled action into my mainspring compressor. I used a deep wall socket to press in on the trigger assembly. That takes tension off the two crosspins that hold the trigger assembly in the spring tube. The two crosspins then came out with finger pressure. Then the trigger assembly came out of the spring tube.
I’m calling this a T05 trigger because that’s what it most closely resembles. But there are small differences, such as the safety bar.
The trigger is a mystery because it differs from every Diana trigger drawing I have examined. It is closest to the T05, and that’s what I’m calling it, but the later T05 (the one on Diana drawings) has a different safety (it looks like a T02 trigger safety) and even a somewhat different trigger blade. The trigger blade in this rifle is plastic.
The two crosspins have been pressed out with the pin punch shown and I am relaxing the mainspring with the compressor.
Trigger assembly is out of the rifle. At the top is the rear spring guide. It appears to be in good condition.
Once the trigger is out the mainspring slides out of the spring tube. I was surprised to see that this spring was not broken as I had conjectured. It is bent in several places and it was very dry. The rear spring guide fits the inside of the mainspring quite well.
The mainspring isn’t broken as I thought, but it is bent in several places. It doesn’t look bad here, but the sides have been rubbed shiny from pressing against the inside of the piston.
If a mainspring appears straight, roll it on a flat surface and watch both ends. They will tell you how flat it is.
Remove the piston
To remove the piston the barrel has to come off so the cocking link can be disconnected from the piston. The Diana 34 has a pivot screw that comes out easily. Thanks, reader JerryC, for telling us about that marvelous Vessel screwdriver!
The piston seal is in perfect shape. However the top is coated with black ash or soot from dieseling. When I looked inside the spring tube the air transfer point is also coated with the same black soot.
The piston seal is fine, but I’ve never encountered the black soot in the center of the piston crown. That inner circle should be silver. There is also black soot coating the air transfer port.
The pivot screw was dry as a bone, but it isn’t the pivot for the barrel. There is a hollow bushing that screw passes through that serves as the pivot. It was also dry as a bone.
The pivot screw and nut and the bushing they pass through. Everything is dry.
With the pivot out the barrel slides out of the action forks. Like everything else, the contact points are dry.
As I separated the barrel and base block from the action forks it became obvious that all the parts were dry as a bone.
RidgeRunner, as I said in Part 2, I don’t think this Diana 34 has been used much at all. As dry as it is I’m surprised by how smooth it shoots. But I think I know why. I will explain in a bit.
I think just lubricating the powerplant properly will probably reduce the cocking effort by 2 or even 3 pounds, but we’ll never find that out because I’m going to install a new mainspring that should take it down a lot more. It was cocking as easily as it did (30 pounds of effort) from the design of the powerplant and nothing else.
The Diana mainspring is made of wire that measures 0.126-inches in diameter. There are exactly 33 coils, so the compressed length of the spring is (33 X 0.126) 4.158-inches. The spring’s outside diameter is 0.825-inches. The inside diameter is 0.565-inches.
The inside diameter of the piston is 0.950-inches, which means there is a huge amount of clearance between the inner piston wall and the outside of the spring. This rifle should have buzzed like a jar full of angry hornets! But it didn’t. Why?
Why so smooth?
The mainspring is kinked on both ends and there are shiny silver spots on the outside of the coil where the spring has been pressing against the inside of the piston wall. That’s what kept the buzzing to a minimum. If the spring had been lubricated it would have been buzzier, not smoother, because the spring would have rattled around instead of pressing tight against the inner piston wall.
The arrows point to the shiny spots rubbed on the sides of the mainspring wire.
There was an extraordinary amount of pretension on the mainspring. It came out of the spring tube at least three inches, if not more. That much is entirely unnecessary. I think Diana used the same spring in several airguns, so the fit isn’t optimum.
Why cocking was hard
Remember in Part Two I mentioned there was a hesitation during the cocking stroke? That was the end of the piston entering the rear spring guide. That would have worn in over time. I can fix it by lightly reaming the opening of the spring guide. What caused the barrel to be hard to break open I have no idea, but I will keep looking.
First I search through my assortment of mainsprings to see if anything I have will do the job. If I find nothing then I buy a mainspring. Beyond that I think the only thing is to clean all the parts, remove as much of the slop in the powerplant as possible and to lubricate properly.
RidgeRunner has a nice Diana 34 that I think I can make nicer for him. We’ll see what comes next.