by Tom Gaylord
Writing as B.B. Pelletier

Part 1
Part 2
Part 3

Diana 45 left
Diana 45 is a large breakbarrel spring rifle.

This report covers:

• Remove the stock
• Action out!
• Action in mainspring compressor
• Trigger assembly is free
• Spring bent!
• Gun is dry
• The rest of the powerplant
• Last word

I’m changing things for this report just a bit. In part 3, I told you that I would do a 25-yard accuracy test next. I’ve decided to forego that step and start working on the tuneup, instead. Today, I’ll show how to disassemble a Diana 45. Make certain the rifle is uncocked before you begin. Do not disassemble a gun if you’re not 100% certain you can put it back together again in safe working condition!

Remove the stock
The first step in any air rifle tuneup is usually removal of the stock; but with the Diana 45, there’s a twist. The stock doesn’t come off like any other breakbarrel stock I know of. Remember, Diana renamed an upgraded version of their model 34 to be the new model 45 when the older model became obsolete. Here, we’re looking at the original Diana 45, so these instructions belong only to this rifle.

To remove the stock, you usually remove 2 screws from the forearm and one or two screws from the triggerguard. Not so with the 45. The forearm screws do come out, but the 45 has a crosspin through the stock that passes through the trigger assembly. It has to be drifted (pressed) out to take the barreled action out of the stock.

Diana 45 triggerguard screw
On the Diana 45, both the front and rear triggerguard screws are simply wood screws. Leave them in the stock.

On either side of the 45’s stock there’s a round, black bushing holding the crosspin. It always looked like a pair of Allen screws to me, but it’s just a metal bushing that holds a crosspin. This pin must be drifted out, left to right, to remove the barreled action from the stock

Diana 45 crosspin bushing
A metal bushing on either side of the stock holds the crosspin that passes through the trigger assembly. The pin must be drifted out.

Diana 45 crosspin coming out
The stock’s crosspin comes out easily with a few taps from the hammer.

Action out!
Now, the action comes out of the stock. At this time, you’ll see that the trigger is modular instead of the swarm of individual parts Diana used in the model 27/35 ball-bearing triggers.

When the action is out, you can look at the trigger housing and see the hole where the crosspin passed through. That will have to be aligned properly when the rifle is installed back into the stock.

Diana 45 hole through trigger
That’s the hole through the trigger housing that the stock crosspin passed through.Don’t confuse that pin with the 2 action crosspins that hold the action together in the spring tube. Both of them can be seen in this photo above the trigger assembly.

Action in mainspring compressor
Next, the barreled action is put into the mainspring compressor. With the compressor’s screw, tension is put on the back of the safety slide, pushing the trigger housing slightly forward (into the spring tube). This takes the mainspring tension off the parts that hold the action together.

You can see a lead block I used in the compressor to make contact with the back of the safety. Putting some tension on the safety slide relaxes the mainspring tension on the 2 Diana crosspins that hold the action inside the spring tube. First drift out the front pin and then the rear pin. If you have enough tension on the safety slide, both pins will almost fall out of the spring tube.

Diana 45 crosspins out
Both action crosspins have been punched out of the spring tube. With just the right tension on the safety slide, they almost fall out on their own!

Diana 45 crosspins
The action crosspins look identical, but I try to keep them in their original holes. Pin on the left goes in the front hole.

Trigger assembly is free
Once the action crosspins are out, the trigger assembly is free to move and come out of the spring tube. It’s what holds the mainspring in the spring tube. Just relax tension on the compressor, and the mainspring starts pushing the trigger assembly out of the tube.

Diana 45 trigger moving
The trigger assembly is backing out of the gun. This photo shows the lead block that’s pushing against the safety slide to hold the gun together now that the crosspins are out.

Diana 45 mainspring relaxed
Here you see the mainspring almost completely relaxed. It has another half-inch to go before being completely relaxed. This shot shows more of the mainspring compressor that’s holding the action together.

Once the mainspring is relaxed you can take the entire barreled action out of the compressor. The trigger assembly is now out of the gun, and its beartrap device spring relaxes. You can see that in the next photo.

Diana 45 trigger unit out
The trigger is out of the gun. You can see the unitized construction. On the left of the trigger unit you can see the beartrap lever sticking up and the spring that powers it.

Once the trigger unit is out of the tube, the mainspring and spring guide can be seen. They now pull straight out of the gun.

Diana 45 spring backed out
There’s the rear of the mainspring and the spring guide. They pull out of the gun at this point.

Spring bent!
Once it was outside the rifle, I examined the mainspring. It looked pretty good until I noticed a bend at one end. That was the end that was on the spring guide. That small bend is where most of the painful vibration came from.

There’s nothing that can be done about a mainspring that fails this way. It failed from time, nothing else. It was just under compression (preload) too long, and the fibers in the steel failed. What I’m saying is that nobody did anything wrong for this to happen. It just did.

Diana 45 spring canted
The bulk of the mainspring is straight. Only the last 2 inches bend. But that’s enough to cause painful vibration when the gun fires.

Gun is dry
The other comment I’ll make at this point is how dry the powerplant is. I found the sticky residue of dried-out oil on some of the parts, but most of the parts were bone-dry. That’s not good. While it doesn’t cause the vibration the owner complained about, it also doesn’t help the gun in any way. When I reassemble the powerplant, I’ll be sure to lubricate every part with the proper lube to keep things running well for decades.

Diana 45 dry parts
The mainspring is dry, the spring guide (silver part above the spring) is dry and the trigger is dry.

The rest of the powerplant
Based on what I’ve seen up to this point, I don’t think this air rifle was ever taken apart. I think it’s just the way it left the factory back in 1988. Yes, the light oils have evaporated and turned to varnish, but that’s all that’s changed.

The next step in the disassembly is to remove the piston, which I was certain would be completely dry and probably also look like new. To remove it means separating the barrel from the spring tube, and then there’s a trick to removing the barrel as well as removing the Diana 45 piston from the gun. There are many more pictures coming in the rest of the disassembly, which I’ll do tomorrow.

Last word
The Diana 45 turns out to be more complex than some other breakbarrel spring rifles. I think taking one apart is a job left to experienced people, so don’t start on yours unless you understand everything I’m saying here. This is not the gun to learn on. Tomorrow, you’ll see more of why that’s true.