Diana 27 - Part 10
by B.B. Pelletier
Well, I cleaned, lubed and assembled the Diana 27 on Monday. Today, we'll see how well it works.
Cocking and firing behavior
You may recall from the early reports that this rifle was firing rough after the breech seal disintegrated following oiling. But after the seal was replaced, it smoothed out again. However, now that I've put black tar on the mainspring and spring guide, there's been a noticeable "quieting" of the powerplant. This is no different than any other spring gun, and it's always such a welcome surprise.
The rifle now cocks quietly, with no noise coming from the mainspring. Firing is absolutely dead calm, like closing a bank vault door. You have to experience this to know what I'm talking about.
You may recall that I adjusted the trigger to a good two-stage release. Now, with the firing behavior being so calm, the 27 is a sheer delight to shoot. The only thing that's missing is a trigger overtravel screw adjustment.
I expected to lose a few f.p.s. with this tune. Not many, but some decrease almost always happens with this kind of tune. However, different spring rifles react differently. As the power of the rifles being tuned increases, the amount of velocity loss with black tar decreases. A Diana 27 is a low-powered rifle, so we can expect to lose 20-30 f.p.s.
All screws tight
You will also remember the lesson of tight stock screws reported in Part 7, where I boosted the velocity about 30 f.p.s., just by tightening the screws. Naturally, the screws were checked before this test.
When this rifle was first tested after oiling the factory breech seal, Eley Wasps averaged 225 f.p.s. After considerable fiddling with various breech seals and stock screws, the average velocity increased to 602 f.p.s.
Following this lubrication, the rifle averaged 598 f.p.s. for the first 10 shots. The spread went from 575 to 625, which is a bit broad. I will say more about that in a moment.
RWS Basic pellets
Seven-grain RWS Basic pellets averaged 212 f.p.s. in the very first test. After all the tweaking, they were up to an average of 655 f.p.s. with a leather breech seal.
The average following this lubrication is 648 f.p.s. The spread is from 630 to 663 f.p.s. If you know much about spring guns, you'll know that the spread is too great. The rifle seems to be breaking in and will require many more shots before the velocity becomes consistent.
Crosman Premier 7.9-grain pellets
Crosman Premier 7.9-grain pellets averaged 321 f.p.s. in the first test and 609 f.p.s. after the leather breech seal was installed and the screws were tightened.
The average after this lube is 586 f.p.s., with the spread from 579 to 596. This is an early indication that the rifle is starting to break in, because it is both noticeably slower than the pre-lube velocity and more consistent than the first two pellets.
RWS Superdomes were the most consistent pellet in the first test, averaging 393 f.p.s. After all the tweaking was done, their average jumped up to 586 with the leather breech seal.
After this lube, the average is 563 f.p.s., with a spread from 552 to 576 f.p.s. Seeing the results from this pellet made me want to test the Eley Wasps once more.
This time the Eley Wasps averaged 577 f.p.s., which is a drop of 19 f.p.s. from the first test in this series. The new spread was from 545 to 601 f.p.s., so the gun is still clearly in the throws of a break-in. I would estimate that it will settle out around 565 f.p.s. when all is finished.
I'm very pleased with what this lubrication has done to this rifle. It's now a very pleasant shooter that can be shot all day without fatigue.
The accuracy hasn't changed, of course. The rifle still has the same barrel and, therefore, the same accuracy as it did from the beginning, though by adjusting the trigger-pull I did make it somewhat easier to shoot accurately.
Was it worth it to lube this rifle? Quite frankly, no. I could have continued to shoot it as it was and enjoyed the gun for many years. However, I did learn about the condition of the interior parts, so that was one benefit from the exercise. And now I know that all the parts are clean and properly lubricated, so that's a second benefit.
Another benefit arising from this lengthy report was learning the importance of the breech seal to the overall performance of the rifle. I can now change the breech seal in my .22 cal. Diana 27 and should see an increase in performance. We shall see, because that's coming next.