by B.B. Pelletier

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7

Today, we’ll revisit our old friend for the part many of you have been waiting for–look inside! This will be a disassembly day, with a description of what to do and how it goes. Before I start, I’m going to gather several plastic Ziplock bags of different sizes to keep all the parts in.

Step 1: remove the stock
Three screws hold the action in the stock. Two at the end of the forearm and the front triggerguard screw are all that have to be removed and the metal comes out. Once out, I began to see the history of this gun. It appears to be virgin–never having been out of the stock before. The insides will tell more.


The action is out of the stock. You can only see one cross pin here because the end cap covers the other one.

There are two crosspins that hold the trigger parts in the spring tube. The trigger parts hold in the mainspring under tension. The back pin is hidden under the sheet metal end cap; once it’s off, you see the pin. But that pin isn’t holding anything, because it falls out on its own. Only the front pin is under tension.


There’s the rear pin!


Which promptly falls out.

Step 2: into the mainspring compressor
The barreled action now goes into the mainspring compressor. Since the 27 is a short rifle, the compressor had to be adjusted for it. When setting up to work on a Diana 27, know that the factory mainspring doesn’t have a lot of precompression. So it will only back out a couple inches when the compressor takes off the tension.


Tension is put on the trigger tube to relieve the single crosspin that holds the trigger parts in the spring tube. I use a lead ingot as a pusher block because it won’t mar metal surfaces.

Step 3: relax the tension and remove the trigger parts and the mainspring
With a Diana 27, you want to relax the spring tension slowly because nothing is held together inside. It all stays together because it’s inside the spring tube, and you’re now taking it out. Be especially careful of the strong trigger spring that is between the dark inner trigger tube and the large silver outer tube.


The mainspring is relaxing. The dark tube you see emerging from the silver tube is the inside of the trigger unit that contains the three ball bearings. Be very careful not to lose them! Also, see how the dark tube climbed up from the silver tube? A strong trigger spring is pushing them apart.


The mainspring is completely relaxed. This is a stroke of about 3.5 inches, so that’s how far the compressor had to move.


There’s the powerful trigger spring. That dark slot is where it fits.


The dark metal tube with the three ball bearings slides out of the silver tube. See that huge “dent” in the silver tube? It’s one of three ramps spaced every 120 degrees around the tube. They control the ball bearings when the dark tube is inside.

Keep all the parts in plastic bags so they don’t get lost.


There are the three ball bearings. When we assemble the gun again, I’ll use tacky grease to hold them inside the dark tube until they’re captured by the gun.


The mainspring has a few kinks, but it’s good enough to re-use.

Step 4: time to remove the barrel
The barrel has to come off to free the cocking link from the piston. When I removed it, there were obvious indications that this rifle had never been apart. Lots of rust in hard-to-clean places and lots of gritty dirt was coming off.


To disconnect the cocking link from the piston means the barrel has to come off the mainspring tube fork. The small lock screw is first, followed by the barrel pivot screw.


When the barrel is removed from the fork, you can see the thrust washers on either side. On the Diana 27, they’re asymmetrical. There are two on the left side and a special formed one on the right. The state of their surface appears to be vintage factory. In other words, the gun has never been apart.


Once the barrel is separated, the cocking link slides to the enlarged hole at the front of the cocking slot and can be removed.


It removes this easily.

Step 5: remove the piston
The piston slides out easily. If you don’t remove the trigger, you have to pull it like you’re firing the gun to clear the piston as it comes out.


The piston is now out. Note that the end of the piston is a mushroom-shaped knob. That’s what pushes the three ball-bearings out of the way (up the ramps) as the rifle is cocked. At the end of the stroke they are pushed into the groove in front of the knob. The pressure of those three balls that have no place to go, holds the piston in place.


You can clearly see the groove where the three balls sit, holding the piston.


The piston seal is definitely leather and looks new! I think it’s original to the gun.

And that’s the sequence of disassembly of the Diana 27. Believe me, it goes together easily too, if you can remember what you did when taking it apart. These photos should guide you.

Cleaning is the next step, and this is a filthy air rifle. There are some dark spots that almost look like moly applied 15 years ago, but nothing else is consistent with that. I’ll continue to observe and see what I find as I clean the gun. I won’t blog that job, but I’ll talk about it in the assembly report next time.