by Tom Gaylord
Writing as B.B. Pelletier
This report covers:
- The breech
- Velocity JSB Exact RS
- RWS Superdome
- RWS Hobby
- Firing behavior
- Cocking effort
- Trigger pull
Today we are back with reader Geo791’s Diana 34P, and we’re looking at the velocity. This is a .22, and a fresh one should produce velocities and power in the same neighborhood as the Beeman R1, but not quite as powerful. George was never concerned about the power of his rifle — only the accuracy that he thought was sporadic. But I do plan to tune his rifle with a Vortek kit that was donated by Vortek for this series, so either way, he wins.
Power has little affect on accuracy. Sometimes if a shot cycle can be smoothed a lot you may see tighter groups, and other times if a weak powerplant is restored to new or better the airgun might shoot better. But typically I tell people that accuracy lies in the barrel and not in the tune. However, just because I say it doesn’t make it so. We shall see.
Before we start I want to show you the breech of George’s rifle. Diana has long been criticized for having an angled breech that deforms the lower half of the pellet skirt when the barrel is closed. Well, on George’s rifle Diana has corrected this.
The breech on this Diana 34P is specially counterbored to allow the pellet to sit deep and miss getting deformed when the barrel closes. The top of the breech counterbore (on the left in this picture) is deeper than the bottom, to make the pellet sit parallel to the bore.
I checked my Diana 34P breech, after seeing this. My rifle is a .177, but there is no evidence that this special “deep seating” breech has been cut in the barrel of my rifle. This is something new.
George complained that some pellets fall out of his breech when the barrel is closed. I found that if I seated each pellet deep into this new counterbored breech with the tip of my finger, nothing fell out! The pellet just has to go in a little farther to be grabbed by the rifling. I have never seen this feature on a 34 before, so I think the new owners of Diana have listened to complaints about pellet deformation and made some changes.
Velocity JSB Exact RS
The first pellet we will test is the JSB Exact RS dome. At 13.43-grains they are light enough to be fast, yet can be very accurate in some airguns. In this 34P they averaged 639 f.p.s. The spread went from a low of 629 to a high of 654 f.p.s. That’s a spread of 25 f.p.s. That much difference is on the high side of normal for a spring gun. At the average velocity they generate 12.07 foot-pounds of energy at the muzzle. That velocity and power are both on the low side for a .22-caliber Diana 34.
The second pellet I tested was the RWS Superdome, and what a difference I saw! This 14.5-grain pellet averaged 701 f.p.s., for 15.83 foot-pounds at the muzzle. That’s spot-on what I expected from a 34! The low was 691 and the high was 707 f.p.s. — a spread of 16 f.p.s. So, the spread is much tighter, as well.
I think George’s rifle is in fine shape. Of course we will see for ourselves when we go inside to do the tuneup. But the chrono numbers look good. This result tells me one more thing. Maybe JSB Exact RS pellets are not well-suited to this rifle! They generate a lot less power and they have a much larger velocity spread. This is why owning a chronograph is so valuable, because it allows you to look inside a gun’s operation to detect small things like the difference between two pellets.
The last pellet I tested was the 11.9-grain RWS Hobby. They averaged 736 f.p.s. The low was 718 and the high was 757 f.p.s., so a spread of 39 f.p.s. That’s large for a spring gun. At the average velocity Hobbys generated 14.32 foot-pounds at the muzzle. That’s on the low side of normal, but after seeing what Superdomes can do I think Hobbys may not be best for this rifle, either.
This Diana shoots very smooth without much vibration. It’s certainly a lot better than a Diana 34 of 1990! I expect the Vortek kit I install to add some power and smoothness to an already smooth shooter.
The Diana 34P cocks with 28 pounds of effort. The cocking cycle is smooth and does not build at any point. The trigger and safety both set without any extra effort.
The two-stage T06 trigger breaks cleanly at 1 lb. 8 oz. That’s so perfect I just hope I don’t screw it up when I tune the rifle. Just kidding, George. Diana triggers are modular and don’t change unless you want them to.
I will have more to say about the trigger when I shoot George’s rifle for accuracy next week. That’s when I get the best evaluation of a trigger, because I’m concentrating on it so carefully.
I will do the accuracy test next. That will be the heart of this report, because it gets to the root of Geroge’s complaint — namely variable accuracy. My plan is to start at 10 meters with 5-shot groups, to get a sense of the pellets the rifle likes and doesn’t like. Then I’ll back up to 25 yards and shoot some 10-shot groups. If I get what I consider a good group (10 shots under an inch at 25 yards with open sights), I will try to repeat it with the same pellet. It isn’t just accuracy I’m looking for — it’s repeatability. George, you correct me if I haven’t got it right.
No scope yet. After we know the accuracy potential I will either be faced with a problem — as in the rifle truly isn’t accurate — or I will know that it is accurate and can proceed to the tuneup. Won’t know which it is until we get there.
After the tune I will retest the velocity with these same pellets. Then, if the rifle is accurate, I plan to mount a scope and do one final accuracy test at 25 yards.
When this test is completed all readers will know several things.
1. How does a Diana 34P in .22 caliber perform?
2. Does the Rail Lock mainspring compressor work on Diana rifles?
3. What is the Vortek tuneup kit like, how does it install and how does it perform?
I am VERY impressed with the quality of George’s Diana 34P! It’s obvious to me that Diana has continued to make small improvements to this, their best-selling air rifle. When companies do that they are setting themselvs up for success!