by Tom Gaylord
Writing as B.B. Pelletier

Diana 35
Diana 35 pellet rifle.

Part 1
Part 2
Part 3

A history of airguns

This report covers:

  • Disassembly
  • Trigger pin
  • Mainspring and guide out
  • Dry inside
  • Out comes the piston
  • Cleanup
  • Assembly and lubrication
  • Mainspring
  • Gettin’ it back together
  • Assembling the trigger
  • Done
  • The difference
  • How does it work?
  • Summary

Today we do something that’s been on my mind for months. This Diana 35 was part of a deal I made with reader, Carel, from the Netherlands. I bought it because I wanted to turn a larger Diana into a sweet-shooting rifle like reader, Michael’s, Winchester 427/Diana 27 that turned out so nice. The Diana 35 is larger than the model 27 and I thought it was quite similar in the powerplant, which would allow me to tune it the same. It turned out there are significant differences between the two rifles that I discovered as I did the work for today’s blog. We are now going to disassemble, clean, and lubricate a Diana 35.

Disassembly

The first steps in disassembly are identical to the model 27. Remove the barreled action from the stock and put the rifle into a mainspring compressor. Two pins hold the mainspring in the spring tube — the same as the model 27, and, just like the 27, the rear pin was so loose that it fell out of the gun after it came out of the stock. Just the front pin held things together. This is where things got different.

Trigger pin

The trigger on the 35 is an assembly held on the spring tube by a cross pin that passes through flanges on the spring tube and flanges in the trigger group housing. The 27 has nothing like that. This pin has to be removed to get the larger ball bearing trigger cage and the piston out of the spring tube.

But the trigger has a stout return spring to be dealt with. When the crosspin comes out this spring takes off like a shot with a departing “ping.” The trigger unit can then be lowered from the spring tube and you’ll find this return spring on the floor over by the kitchen sink.

Diana 35 trigger pin
The cross pin (yellow arrow) holds the trigger assembly to the spring tube. It’s under a lot of tension from the trigger return spring (blue arrow). The cross pin has to come out for disassembly. Don’t worry about the return spring — it self-disassembles!

Diana 35 trigger out
The Diana 35 trigger is an assembly that comes out as a unit.

Now there was clearance in the spring tube for the other parts to slide out. Tension was put on the trigger cages inside the tube and the second powerplant crosspin fell out on its own. Then it was just a matter of backing off the tension of the mainspring compressor and the mainspring pushed everything out of the spring tube.

I had to use a short metal pusher (blue arrow) to press against the trigger cages because, unlike the 27 trigger, the 35 trigger cages are about a half inch inside the spring tube when the rifle is together. On the 27 the black inner ball bearing cage is outside the spring tube when the powerplant is together and can’t be pressed by the mainspring compressor directly.

Diana 35 trigger cages emerging
A metal pusher (blue arrow) connects the mainspring compressor to the inner black ball bearing cage of the 35. This photo also shows the spring that pushes the two cages apart. There is a short spring guide inside this one.

Diana 27 end cap off
This is a Diana 27 that’s still assembled but the end cap is off. You can see the black inner ball bearing cage that the mainspring compressor presses against.

cages with spring
The Diana 27 has the same two bearing cages with a spring pushing them apart, but there is no spring guide for this weaker spring. The arrow points to the place where the trigger blocks the silver bearing cage.

Diana 35 trigger parts
There are the two bearing cages, the bearings and the spring that pushes them apart with its guide. The difference between the 35 and 27 triggers is the strength of the coiled spring, the guide and the diameter of the silver outer cage.

Mainspring and guide out

Once the trigger cages are out the mainspring its spring guide comes out of the rifle. Was it broken like BB thought? Was it bent/canted?

NO! It’s straight as an arrow and fully serviceable, if not as powerful as a new spring. I could not have had better luck!

Diana 35 mainspring and guide
The mainspring is still serviceable. I see some partially collapsed coils on the both sides, but the spring is still straight. It will go back in the rifle.

Dry inside

The spring guide fits very tight inside the spring, which is a good thing. But there is no lubrication! This powerplant is bone dry! I think this might be the first time this powerplant has been apart, because there is varnish from old oil on some of the parts, and no fresh lubrication. That’s a Diana factory trait from this era.

Out comes the piston

To get the piston out the barrel has to be separated from the spring tube. I noticed as I did this that the pivot washers were lubricated with oil. They should have some grease in there and moly is recommended, but from the 1950s to the ’70s, oil was how it was done.

Once the barrel was off the gun the cocking link came out of the piston and the piston slid out of the spring tube easily. At first it looked corroded, but that was just dirt that wiped off with a rag. The piston was clean and just discolored from assembly

Diana 35 piston
The piston was bright after a wipedown. The discoloration is a result of heat during manufacture. The leather seal is in good shape.

Cleanup

The disassembly took about 30 minutes, including the pictures. Now it was time to clean all the parts. For the most part, all that was needed was to be wiped with a clean rag. But the inside of the compression chamber took a little more than that. I sprayed Gun Scrubber inside and then wiped it dry with paper towels wrapped around a long dowel. That got most of the dirt. I thought there was some lead smashed against the end of the compression chamber, but after a good cleaning it looked fine.

But the outside of the spring tube had some heavy active rust spots. These I sprayed with Ballistol and then scraped with a flat screwdriver blade. When all the bubbly rust was gone I went over everything with 0000 steel wool and Ballistol and the metal emerged smooth again. There was some loss of blue and some pits.

All the cleaning took about 30 minutes. It was time for assembly.

Assembly and lubrication

Assembly and lubrication took about three hours. I will describe the tight spots as we go. First the piston was lubed with moly grease around the front by the seal and around the rear. The piston then dropped back into the spring tube almost by itself.

The barrel and spring tube went together at this time, so the cocking link could be joined to the piston. I lubed both pivot washers, inside and out, and also the pivot bolt before sliding it back through the holes. Now the mainspring could be put back in the gun.

Mainspring

I lubed the mainspring with Tune in a Tube grease, which was my goal back in February, when this project was first dreamed up. I lube the front half of the spring, then stick it inside the spring tube and lube the back half. That way my hands don’t get too greasy.

Diana 35 spring
I lube half the spring then stick it inside the powerplant and lube the other half.

Gettin’ it back together

Once the mainspring is back in the rifle, the ball bearing trigger cages go back inside. This was my first major challenge. The 35 trigger cages are under more spring pressure pushing them apart, and they have to be installed in the rifle so the crosspins that hold them inside the spring tube will align. Don’t forget that spring guide for the two bearing cages that makes the assembly even harder. All of that took me half an hour to figure out. And I could have used a third arm!

Once everything was inside the gun I inserted the front crosspin. I didn’t bother with the rear one because it would just keep falling out on its own. Now it was time to install the trigger assembly. Remember that stiff trigger return spring that tried to escape?

Assembling the trigger

The trigger is a unit, so no problem there, but the flanges and holes in the trigger unit have to align with the flanges and holes on the spring tube. Problem!

I fiddled and fussed for 45 minutes trying to get those holes to align with that powerful return spring pressing everything out of the way. Then the lightbulb went off and I got a small clamp. It isn’t easy to clamp to a spring tube, but it is possible and I almost got the unit on before the return spring decided to take another trip. Oh, well!

Then I installed the unit without the spring, which was easy and tried to manually compress the spring into place, which wasn’t. In all I spent more time doing this one thing than any other part of the entire process.

Done

In all it took me about 4 fours, start to finish, to work on this airgun. This is one I recommend you don’t try as your first project. Do a couple 27s before tackling one of these.

The difference

Let me show you the big difference in the Diana 35. Aside from the more powerful mainspring it all comes together at the rear of the spring tube.

Diana 35 spring tube
The Diana spring tube is thicker-walled and has two flanges (arrows) to which the trigger assembly attaches. The tube is longer in the rear so the ball bearing cages for the trigger sit deeper inside the spring tube.

Now the barreled action goes back into the stock. The rifle is assembled.

How does it work?

We will need to test how this rifle works, but for now I wanted just to see if everything had gone together as it should. So I cocked it and loaded a pellet. The trigger is now lubricated so I expected it to work a little smoother, but it’s too soon to tell.
The rifle fires with very little vibration. There’s still a noticeable forward jump, but the powerplant is quiet and smooth. And it still cocks with very little effort. Like I said, I will test it for you, including an accuracy test that stretches back to 25 yards.

Summary

Right now I am cautiously optimistic. This Diana 35 behaves very well. It’s not as smooth as Michael’s rifle, but I don’t think it’s lost very much power, either.

We shall see.