by Tom Gaylord
Writing as B.B. Pelletier
Michael’s Winchester 427 is a Diana model 27 by another name. The rifle pictured is my Hy Score 807/Diana 27
A history of airguns
This report covers:
- Michael’s Diana 27
- Out of the box
- Flat breech seal
- No baseline test
- Onward Through The Fog
- Remove the action from the stock
- Action into the compressor
- Remove the piston
- Disassembly complete
- List of jobs
Michael’s Diana 27
Some time back, reader Michael mentioned some problems he was having with his new/old Winchester 427, which is a Diana 27 by another name. I offered to tune it for him because it’s been some time since I have been inside a 27. There are many new readers who are not aware of this wonderful air rifle, and I thought it was time they learned about it.
Diana made the model 27 for a great many years after WW II, and they made them for a number of other companies, as well. The guns were made in both .177 and .22, but Winchester and Hy Score only ordered them in .22 caliber, so a 427 and an 807 are always .22.
Out of the box
When I unpacked the gun it looked pretty good, so I gave it a thorough once-over. The metal was lightly speckled with surface rust, but it wasn’t too bad. The rear sight was missing its rear mounting screw, which allowed it to move side to side and also up and down, and the spring that keeps tension on the rear sight leaf is not installed properly. There is a spring stuffed inside the sight, but it isn’t in the right place and it doesn’t look like the correct spring. Also the windage adjustment screw that should be fastened to the sight by a small circlip is wired in place, instead.
The barrel pivot bolt should have a locking screw to hold it in place. Also the rubber bumper that goes on the butt to keep the rifle from slipping on the floor is missing.
The rear sight is missing the back anchor screw (arrow) and a spring that goes up front is not mounted correctly. The barrel pivot locking screw is also missing (arrow).
Flat breech seal
The last thing I’ll note is the breech seal. On this rifle it’s quite flat and lifeless. It seems to be a synthetic seal and I will probably replace it with a leather seal that is longer-lasting and seals better.
The breech seal is very flat and lifeless.
No baseline test
I had hoped to baseline the velocity of the rifle today before I started the work, but it detonated on the first shot and I decided not to. It vibrated and sounded like a dry-fire, which I will guess is mostly due to a large loss of air at the breech. I don’t want to shoot it in this condition.
If you want to learn to rebuild spring piston airguns, this one isn’t the place to start. The trigger is quite complex until you understand how it works. When you do understand that the rifle becomes simple to work on. You will need a mainspring compressor for this gun.
Remove the action from the stock
The first step is to remove the barreled action from the stock. That’s two stock screws on the forearm and the forward triggerguard screw. Once the action is out, the sheetmetal end cap slides off and the rifle is ready for the compressor.
Action into the compressor
Now the action goes into the compressor and comes apart. The trigger parts are first to leave the spring tube.
With the end cap off you can see the second cross pin that holds the action together. You can also see some of the 48-year-old oil that has hardened into varnish and is holding things together.
The action is ready to go into the compressor. When it does, the compressor will press on the inner trigger cage (two arrows) until the tension on the two pins is released. They will practically fall out of the gun at that point.