In search of the “perfect” tune
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.
This report covers:
- The fix
- Michael’s rifle
- Then came Carel
- But wait…
- While I’m at it…
- My first 35
- Blue Book
Tuning Michael’s Winchester 427/Diana 27 really ignited a spark in me! That’s why I linked to all the reports. It put me in mind of many things I have experienced over the years. The one that stands out the most is the Diana 45 I tuned for Johnny Hill of Tin Starr Bullets in Weatherford, TX back in 2015. His rifle was bone-dry on the inside and also had a classic Diana bent mainspring. I say classic because when Diana started the velocity race against the FWB 124 in the 1970s, they over-hardened their mainsprings with the result they always bent or broke off at both ends.
I buttoned the piston of Johnny’s 45, which tightened the piston-slap tolerance immensely. I also installed a much tighter spring guide that eliminated more of the vibration. There is a video of me showing just how tight the new guide is in Part 6. Then I lubricated the powerplant.
If you want to see everything I did to that rifle go back and read all the reports. It is one of the best tuneup reports I have ever written, plus there are a couple videos of me assembling the powerplant.
That rifle proved extremely accurate but still buzzed just a bit when I finished. This was in 2015, in the days before I knew about Tune in a Tube, so I used heavy black tar grease, which is mostly open gear lubricant. It quieted the powerplant and only lost a little velocity.
Then I tuned Michael’s rifle. It was even quieter than the 45. He should get it back today and I’m sure he will tell us what he thinks. When it left here it was the smoothest Diana 27 I have ever shot. And doing that tune, with all the challenges, awoke an interest in me. I like the Diana 25/27/35 powerplant and want to do more with it in this historical section.
Then came Carel
Reader Carel from the Netherlands responded to my open wish to tune a Diana 35 someday and told me he had a nice one for sale. We started talking. Many readers actually saw his contact in this blog. Let me share with you what we discussed.
He first told me about his Diana 35. It’s an older one with some things I have never seen, such as “ears” to protect the rear sight. It also has a very European style stock instead of the fatter stock that I knew.
Carel’s Diana 35 is a beautiful old gun.
This old rear sight on the Diana 35 has protective “ears” around it. This is a feature I’ve never seen.
The really nice aspect of this 35 is the stock is slim. Unlike the heavy stocks we saw here in the U.S this is, “… an elegant weapon for a more civilized age,” to quote Obi Wan Kenobe from the Star Wars film, A New Hope. It looks much closer to the Diana 27 stock that I’m familiar with.
My plan both was and still is to tune this rifle (Carel’s 35 that is now mine) for smoothness and not power. I will look into reducing the tolerances of the powerplant, but not at the expense of increasing the cocking effort. I have owned a Diana 35 before and found it too hard to cock and far too harsh to shoot for the minimal power increase it gave over the 27. Well, I don’t need power. Ask reader RidgeRunner — he knows! These older airguns can be a sheer delight to shoot, as long as they are kept within the originally designed performance parameters.
… there is more! Carel also told me he also has a Diana 27S for sale. I had to go to the Blue Book of Airguns for that one! It’s a 27 that has a two-piece articulated cocking link that allows the cocking slot in the stock to be shorter. That makes the stock stiffer and, in turn, reduces vibration. We didn’t see the 27S here in the U.S. that I am aware of, so it is an uncommon airgun. Carel tells me it’s uncommon in the European Union, as well.
The Diana 27S has a blockier forearm for a reason. Note the squared triggerguard. It’s like the guard on the Diana 45.
The Diana 27S cocking link is two-piece which allows the cocking slot to be shorter. The theory is a shorter slot makes a stiffer stock that reduces vibration.
Of course I bought it, too! Carel offered it for a very reasonable price and I wanted to get it to show to you (I think he wants that, too). I have never seen a 27S that I am aware of, so this will be a new experience for me. To paraphrase the limbo song, “How smooth can I go?”
While I’m at it…
So then he tells me about his Diana model 26. WAIT — a Model 26??? I grab the Blue Book and, sure enough, Diana did make a model 26. Of course we know from the Blue Book that FWB also made a model 125 (in 5mm) that went with their 124 and 127. Those few rifles were made as samples for Dr. Beeman who wanted them in his catalog because he was a big proponent of .20 caliber/5mm. Only a handful were ever made. What about the Diana 26?
The Blue Book says the modern ones (there are also older Diana 26s that are nothing like the modern one) were made from 1984 to 1992. I guess they were imported by RWS USA, who imported all Dianas for many years — I just never heard of the 26. I own a 25 and a 27 and I’m aware of the 24 and 28. This 26 seems like the missing link to me. It was for sale so of course I bought it, too. So, there are a raft of old vintage Dianas coming your way this year.
Diana 26. You know as much as I do about this one.
Once the rifles arrive I will try to make sense of them and form a plan of action. I need the chance to hold and shoot each of them before deciding what comes next. But I will test each of them for you in the conventional way — Part 1 a general report, Part 2 velocity and Part 3 accuracy. As long as the guns work, that’s the least I can do.
I just finished doing a conventional lube tune on a 27, and it turned out very well. Now maybe I can try something different. My goal will be to reduce vibration to a minimum while retaining as much velocity as possible. I will not attempt to get higher velocity, because I have learned through experience that these vintage airguns are not right for that. Also, I want the cocking effort to be low because the shooting experience is much better when it is.
My first 35
As I mentioned, I have owned a Diana 35 in the past. Mine was a Hy Score model 809. When I owned that gun I knew far less about Diana springers than I do today, but also that was a different time than today. We were caught up in the unending pursuit of power, which means velocity in pellet guns. And the Diana 35 has a fatal flaw when it comes to velocity. Its piston stroke isn’t long enough to generate much power. The Diana 34 that followed it years later did just one thing — increase the piston stroke, and the rest is history.
Quick — what do people do to try to generate more velocity from a spring gun? That’s right, they install a stiffer mainspring. Doing that to a Diana 35 means you get a breakbarrel that’s hard to cock and one that buzzes like a mason jar full of hornets. But there is not much more power.
My .177 caliber 35 shot 8.2-grain RWS Meisterkugeln pellets at about 590 f.p.s. When I disassembled it I found a rusty piston (Michael, yours wasn’t the only one) and thick lubrication that had caked. The cocking effort was 24 pounds, which doesn’t seem that high until you cock a 27 that’s under 20 pounds. After cleaning all the parts, lubricating with moly grease and black tar, the cocking effort dropped back to 19 pounds and the velocity remained almost the same — just a few f.p.s. less.
What I would like is a 20 pound cocking effort and a dead calm shot cycle. I don’t care what the velocity is (somebody call the velocity police right now!). Because it is a 35 I know it should be at least as fast as a 27 and more than likely a little faster — but as I said, I really don’t care. I want what Michael now has. The early slim stock is a plus I will need to experience to appreciate.
I will leave you with this. The Blue Book of Airguns that I’ve mentioned is being updated this year and I’ve been asked to cover what is new since 2016. Well, it’s too much to cover, so I’m putting my report into categories like compressors and price-point PCPs and so on. You can expect to see a new edition this May or June, so start saving your pennies.