Checking out a Diana RWS 34P: Part 5
by Tom Gaylord
Writing as B.B. Pelletier
This report covers:
- How to tell if the mainspring is broken
- Tight piston seal
- JSB Exact RS domes
- RWS Hobbys
- RWS Superdomes
- Where are we?
- Did the rifle smooth out?
- Cocking effort
- What are the advantages?
- The rest of the story
Today we look at the results of yesterday’s tune on Geo791’s .22 caliber Diana RWS 34P. I talked to Tom Gore, the owner of Vortek, and asked what kind of results I could expect from this kit. He said this one was designed to make the rifle perform at the factory spec, but with much longer spring life. When I told him how the rifle had tested before he said he felt it was right on spec already. I felt so, as well. And of course that was with a broken mainspring.
How to tell if the mainspring is broken
Several of you have asked me whether it’s possible to know when a Diana mainspring has broken and I said no. If just one end of the spring is broken the gun will shoot smoother than before and will have the same velocity. I think the broken piece winds itself into the new end of the mainspring (it always does) and helps dampen vibration. Unless you are observing the performance of your rifle very carefully and watching for this you’ll never see it.
Of course when the other end breaks, as it often does, the rifle gets even smoother and easier to cock. But at that point a .22 will lose about 150 f.p.s.
So, Georges’ rifle was both smooth and powerful when I initially tested it. I said that in Part 2. Let’s see what the Vortek tune did. I will test it with the same pellets I used in Part 2, so everything is the same except the tune.
Tight piston seal
Several readers asked about the possibility of putting an o-ring in the groove that runs around the circumference of the piston seal. That is impossible. This new seal fits the compression chamber extremely tight. I had to use a screwdriver to ease it past all the cutouts in the spring tube, so the seal did not get cut.
That groove sqwishes down much smaller when the seal goes into the spring tube. It’s there to prevent excess lube from migration forward. George won’t have to worry about that because I applied the special grease very sparingly.
JSB Exact RS domes
The first pellets I tested were JSB Exact RS domes. They averaged 639 f.p.s. in the before test, with a 25 f.p.s. spread. This time they averaged 627 f.p.s. and the spread was 28 f.p.s. — from 613 to 641 f.p.s. That’s a bit of a drop. Before it produced 12.07 foot-pounds and this time it produced 11.73 foot pounds
RWS Superdomes were next. These 14.5-grain pellets averaged 701 f.p.s. in the first test and 689 f.p.s. with the Vortek tune. The spread was initially 16 f.p.s. and this time it was 62 f.p.s. because of one slow shot. That one went 641 f.p.s., but it was an anomaly because the next slowest shot was 689 f.p.s. The high was 703 f.p.s. In the first test this pellet developed 15.83 foot pounds. After installation it develops 15.29 foot pounds.
Next up were some 11.9-grain RWS Hobbys. In the before test they averaged 736 f.p.s. with a 39 f.p.s. spread. This time Hobbys averaged 727 f.p.s. and the spread was 37 f.p.s. That’s pretty close to last time. The muzzle energy was 14.32 foot-pounds in the first test and 13.97 foot-pounds this time.
Where are we?
I bet you didn’t expect those numbers — did you? I didn’t either. I do know that as this tune breaks in after several hundred shots the average velocities will rise just a bit, perhaps to where they were with the factory mainspring.
Why isn’t it any faster? Well, in my experience this Diana 34 was right where I expect all the good ones to be. Making it go faster serves no purpose unless it comes with some kind of benefit, like improved accuracy or smoother operation. Since tunes seldom affect accuracy I doubt a faster gun would offer us anything, and it is already shooting very smooth.
Did the rifle smooth out?
It’s difficult to say whether the rifle smoothed out because it was smooth before. I told you that when I tested it. Smooth shooting is one characteristic of Diana rifles that have broken mainsprings. They are already very smooth from the factory and when the spring breaks they get very calm.
So — is this rifle any smoother? I’m going to stick my neck out and say yes. I believe it is. The difference is very small because the rifle didn’t have very far to go, but I do believe I can feel a small improvement.
Here the Vortek kit will suffer, because the rifle with the broken mainspring was already cocking very easy. Diana’s always get easier to cock when the spring breaks. I measured the force needed to cock the rifle now and it comes to 35 pounds on my bathroom scale. Before it was 28 pounds. So the effort has increased. Diana rates the cocking effort of a model 34 at 33 pounds, so one might say the rifle is back to factory specs.
What are the advantages?
This test has produced some surprising results, hasn’t it? We all want the ending to be like when Bob Beamon broke the world long jump record at the 1968 Olympics by almost 2 feet, but life isn’t always like that. Often the victory is measured in inches and sometimes, like today, it stays the same or even goes backwards. So, has anything been gained?
Absolutely! First, take another look at Geroge’s broken mainspring. Not only was one end snapped off, the other end is canted and will probably break as well. The Vortek kit has put an end to that fear. George’s 34P will still be shooting this fast or faster 10,000 shots from now.
Next, the powerplant has been lubricated for an indefinite period. George never has to worry about oiling the piston or greasing the mainspring because the materials I’ve installed probably have a good 10 years of life in them — maybe more.
And finally, the rifle does shoot very smooth. This time it’s not because of a broken part but because all the tolerances have been reduced to a minimum and then lubricated with just enough of the right grease.
The rest of the story
I said in an earlier installment that I have a plan to fix George’s drooping problem for him. I’m not going to tell you what it is today, but next time I will mount a scope that’s similar to the 4-12 George owns, and shoot for accuracy at 25 yards again. We now know which pellets it likes.
If everything works as planned, the mount I will use will allow the scope to be adjusted in the center of its elevation range, which may help George with his fliers. The mount maker has agreed to donate this mount to George, so when he gets his rifle back all he has to do is remount his own scope.
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