Diana 27 - Part 9
by B.B. Pelletier
Before I begin today's report, here's some news for those awaiting a Benjamin Marauder from Pyramyd Air. Pyramyd Air has sold out its initial allotment of guns. If you placed your order by May 7, you're supposed to receive one of the initial allotment of rifles. All orders placed after that date should expect shipment by around June 21.
Crosman is overwhelmed with orders for the new rifle, plus they're getting their production line up to speed. Therefore, it will be several more months before they will be able to fill all the backorders. The best we can advise is to order your rifle soon to get a place in line for the next batch of guns.
In this segment, I'll clean, lubricate and assemble the .177 cal. Diana model 27 I took apart in Part 8. I have a deep dark secret. As much as I talk about Diana 27s, I actually have a slight fear of them when it comes to assembly. Even though I have long since learned all of their secrets, I don't like the way they go together, and I find the challenge of assembling one unpleasant. Give me an R1 any day!
But I promised this and the rifle was in pieces, so I had to do it. This tune, which is nothing more than cleaning and proper lubrication, differs from what I did to my .22 caliber Diana 27 many years ago. I did that rifle before black tar was discovered, so I used a light lithium-based grease the Army used to supply for M1 Garands. I have a can that I've owned for 40 years, and it has served me well for light grease jobs like the model 27. But this grease, being light, constantly migrates forward into the piston seal, keeping it well-lubed all the time. So, my .22 Diana 27 (actually a Hy-Score 807) is one springer that never needs a drop of oil. It has its own reservoir of lube that will probably last a couple more decades.
I wanted to lube this .177 model 27 in a more contemporary way, to contrast with the other gun. I will show you what I did as we go. Of course, I've chronographed the rifle very thoroughly with several different breech seals, so I'll compare the velocity and firing behavior after this job is complete.
First, we'll clean
You may recall from Part 8 that this rifle was very dirty. I discovered it during the disassembly. The first thing I had to do was clean everything so the new lube wouldn't contain any abrasive dirt. The compression tube is always the big thing to clean because you have to reach deep inside to remove everything. My approach has always been to wrap a strip of paper towel around a dowel or, in the case of this rifle, a cleaning rod. Use a rubber band to secure it. Then, saturate the tip with rubbing alcohol and wipe out all the dirt and old grease. This way is quick and clean because you can replace the paper towel as many times as it takes. The alcohol evaporates almost immediately, leaving the metal clean and dry.
When you finish, the inside of the spring tube will shine like a mirror--especially if the rifle is a Diana 27. After finishing that task, use the same paper towels and alcohol to wipe all the other parts. The piston and mainspring are the two hardest parts to clean after the compression tube, but they're really no trouble at all.
I also cleaned the bore with a brass brush and J-B Non-Embedding Bore Cleaning Compound. Before this cleaning, the bore didn't look very shiny. Afterward, it did.
When everything is completed, it's time to lubricate the parts and assemble the rifle. The piston goes first.
Like many spring gun pistons, the Diana 27 piston only contacts the spring tube at each end. The center is smaller, so only the enlarged ends need to be lubed. I use Beeman M-2-M moly grease for this.The piston seal is leather, as we discussed in Part 8, but I still coated it with moly grease. I know this will be transfered to the compression chamber wall, which is what I want.
I had a hard time finding the moly paste on the Pyramyd Air website, because they didn't list it under the lubes (the word paste probably threw them). They put it in the correct category this past weekend. When you can't find something on the Pyramyd Air website, type the product name into their search window. That often takes you right to it--if they carry what you're looking for.
Once the piston's in the gun, you can connect the barrel to the mainspring tube. This rifle has asymmetric thrust washers between the baseblock and the mainspring tube forks. On the right side, there's one shaped washer that conforms to a complex shape on the baseblock, but on the left side the washers are mostly flat. One of the left washers has some spring built into it to keep tension against the forks.
Before fitting the baseblock inside the mainspring tube forks, connect the cocking link. Once the baseblock is in, you cannot maneuver the cocking link to the entrance hole.
I coated all washer surfaces with moly grease. Fitting the baseblock back into the mainspring forks with washers on both sides of the baseblock is somewhat tricky, because those washers will be under some tension when inside the forks. You have to "shoehorn" them in, which means once the edges on both sides of the base block are started, the washers are easier to manage.
With the barrel in the forks, it's easy to install the pivot bolt and its locking screw. Put moly paste on the shaft of the bolt before inserting it.
At this point, the mainspring is installed. Although my factory mainspring was canted a bit, I used it because I didn't have a replacement on hand. I lubed the spring and spring guide with black tar for vibration dampening.
Here comes the hard part
Now, the gun is ready to be closed. The trigger is what holds everything together and in a Diana 27 the trigger is composed of many separate parts. I used to think the three ball bearings were the hard part, but an old mechanic's trick solves that problem. Simply put lots of grease into each hole in the black cylinder, where the ball bearings ride and stick them in the holes. They won't move during assembly.
However, the ball bearings are nothing compared to the trigger spring. It fits into a long slot on top of the black cylinder, but it acts upon the larger silver cylinder, as well. It moves the black and silver cylinders apart when the gun is fired. Cocking forces the two cylinders together, putting tension on the spring. This powerful trigger spring is actually held in place by the space BETWEEN the silver cylinder and the smaller black cylinder that rides inside it. The piston rod keeps the black cylinder aligned. It's a complex arrangement.
Once the trigger parts are inside the mainspring tube and the long slots in the silver tube are aligned with the two holes in the mainspring tube, you can start squeezing them together with the compressor. Remember that you have to pull the trigger to get it out of the way as the parts go together.
An alignment pin will help you line up the pin holes in the mainspring tube with the slots in the silver tube and the two pin holes in the black tube. Jiggle the tubes until they seem aligned, then adjust compressor tension until they're aligned perfectly.
At this point, I should tell you that the rear pin is fatter than the front one. So, don't put them into the wrong holes. The front pin may go in first, but the rear pin has more slop in the fit and usually goes in first. Consider it an assembly pin. After the front pin is in, the rear pin becomes loose and will fall out until you put the end cap back on. The front pin is the only thing holding the action together.
After that, it's just a matter of installing the action into the stock and the job is done. And how did I do, you ask?