by Tom Gaylord
Writing as B.B. Pelletier

Diana 27
Michael’s Winchester 427 is a Diana model 27 by another name. The rifle pictured is my Hy Score 807/Diana 27

Part 1
Part 2
Part 3
Part 4

A history of airguns

This report covers:

  • SHOT Show
  • Today and Monday
  • New parts
  • Scragging?
  • Lubricating the mainspring
  • Rust removal
  • Lubrication
  • Putting the piston into the spring tube
  • Pull the trigger!
  • Attach the barrel
  • Break

Many of you have been reading this series in which I tune reader Michael’s Winchester 427 that is actually a Diana 27. This is not an air rifle for beginners to learn on! The mechanism is too complex for first-timers for a number of reasons that should become clear today.


I have to tell you — this is a very lengthy report. I won’t get it all done today, so Monday I will finish up. And on Monday I will be in Las Vegas at the SHOT Show. I won’t see your comments as frequently as usual while I’m there next week, plus after I walk out of the show every day I have to go back to my room, write the next day’s blog and have it ready to publish by 9 p.m. which is midnight on the east coast where the WordPress server publishes the blog. So please don’t ask me any lengthy questions. I am not going to have dinner with anyone this year, so I can do my work without being whipsawed!

Today and Monday

Today and Monday could be called, “Putting her back together,” because that is what I am going to do. In Part 4 you read and saw how I cleaned the major parts. They were rusty, but by soaking them in Ballistol for many days the rust loosened and came off quite nicely, revealing a gun that really has not been shot or used that much. I have certainly seen others that were a lot more worn.

Several readers asked me to show how I lubricate the gun parts as they go back together, and that is a big part of what I will do today and Monday. I will also pass along some tricks of the trade that will help you in the assembly process. Let’s get started.

New parts

I have already told you that I’m installing a new piston and piston seal assembly. You can see both of those in Part 4. Michael also sent me a new mainspring that he obtained from Chambers in the UK. It is not yet scragged (shortened by compression), so it will be harder to install than the old spring would be. The old spring is in good condition and would be fine in this rifle, too. But Michael bought the new one and that’s the one going in.

Diana 27 springs
The new mainspring (bottom) is longer now because it has never been scragged. After being inside the rifle a few days it will become about as long as the old spring.


Should I have scragged the spring before installing it? It would have made installation much easier. To learn more about scragging, read this report.

Lubricating the mainspring

Many of you wonder how much lube to put on a mainspring. Some also wonder what lube to use, but a regular readers knows I recommend Tune in a Tube (TIAT) grease that’s available here at Pyramyd Air. If you are an overseas reader or if you want a lifetime supply of the stuff it is Almagard 3752 grease. I have written a lot about how well it works — now let’s see how much we should use.

Diana 27 lubing mainspring
Here you see the lubed spring on the right and the dry spring on the left. This is lubing “sparingly”, which is all the Diana 27 spring needs.

The Diana 27 is neither powerful nor is it notorious for vibration, so the spring doesn’t need that much grease. And Tune in a Tube is probably different than any grease that most of you are used to. It’s extremely tacky and doesn’t vibrate off. It doesn’t take very much to quiet any vibration, so use it sparingly. Because of its nature, you’ll use more than you intend, so apply it lightly and spread it around.

You will note that I did not lube the inside of the mainspring coils. But I did lube the spring guide and the piston rod with TIAT. They will transfer their grease to the inside of the spring coils as the rifle is cocked and fired. If I was using white Lithium grease I would have lubed the inside of the spring coils.

I lubed half of the spring, then stuffed it into the piston that was already inside the rifle (I haven’t discussed that yet). That held it so I could lube the other half and not get too much grease on me.

Rust removal

I mentioned using Ballistol to remove rust from the parts. The other thing I used was steel wool. I used OOOO wool on the inside of the spring tube and I used a stainless steel pot scrubber on the other parts. The parts were coated with Ballistol when I rubbed them. I will show just one so you get the idea.

Diana 27 spring guide before
The spring guide was rusty before the cleaning. It’s not bad, but look at what can be done.

Diana 27 spring guide after
After cleaning the guide with Ballistol and a stainless steel pot scrubber, look how clean it is.


All the other parts were cleaned in this same way. That gave them clean surfaces for the lubrication. Like I said — TIAT on the spring guide and piston rod, as well as the mainspring.

The inside of the spring tube was coated with a thin coat of Moly grease. Now, molybdenum disulfide is not grease. It’s a dry compound that bonds with steel to form a low friction surface. The grease is the vehicle that the particles are mixed in that allows the moly to be applied more easily. To apply it to the inside of the spring tube I use a thin wooden dowel that’s wrapped with a bit of paper towel at the end. I can then swab the moly on the inside of the spring tube like using a giant cotton swab.

Diana 27 moly
Coat the paper towel with some moly and then spread it all around the inside of the spring tube.

I used to also coat the piston with moly front and back until I realized that the piston seal prevents the front of the piston from touching the interior spring tube walls. That’s part of its job. Now I only coat the flared rear section with moly. It conceivably touches the inside of the spring tube from time to time, because small scratches in the blued finish on the inside of the tube show it. Read Part 4 to see what I’m talking about.

Putting the piston into the spring tube

This is where the assembly begins. The new piston with its new leather seal has to go inside the spring tube first. I have soaked that leather seal in light oil for several days, so the leather is soft and pliable. The insert inside the seal (see Part 4) keeps it from collapsing in on itself.

The seal appears to be larger than the spring tube because it is full of oil, but it is also very pliable like a loaf of soft bread. I insert three-quarters of the seal into the end of the tube, then use a flat-tipped screwdriver to press in the other quarter as I gently push in on the piston. This is a careful technique like putting on an expensive pair of new leather shoes with a shoehorn. You don’t want to damage or distort anything and if you work carefully you won’t need to.

Pull the trigger!

As you press the piston into the tube it soon comes in contact with two hooks on the end of the trigger. I will explain what those hooks do in a bit. Pull the trigger back to move the hooks out of the way and keep pressing the piston into the tube. Watch each open window in the spring tube, to make sure the leather seal doesn’t hang up on any sharp edge that will shear off some leather. Use the screwdriver to press the seal back into the tube at these points. At some point the piston will go all the way into the tube where there is no more worry. Use the mainspring to press it in when you can’t push it with your hand.

Attach the barrel

Once the piston is in the tube, attach the barrel and cocking linkage. The end of the cocking link is flared and the front of the cocking slot has an enlarged hole through which the flared end of the linkage must pass. The flare keeps the cocking link inside the spring tube as the rifle is being used. Coat the flare top and bottom with moly grease that will transfer to the piston and the inside of the spring tube where there is already some moly.

Once the link is attached put moly on both sides of both base block (the section that holds the barrel and the pivot bolt) where the washers go and slide the base block into the spring tube fork. On some guns the washers will walk out of position, but the Diana 27 washers fit in machined recesses on either side of the base block. The washers are different, so each one only fits one side of the base block. The moly grease will hold them in position during this operation.

The last thing is to put some moly on the pivot bolt and screw it tight. The Diana 27 has a place for a locking screw to hold the pivot bolt in place, but Michael’s gun did not have one when I got it. As long as he watches the tightness of that bolt there shouldn’t be a problem.


I will end this report here because the next part involves putting the trigger together and is very long. You have already seen several things that might be called tricks of the trade. On Monday there will be many more! Have a great weekend and I’ll see you next week.