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Ammo RWS Diana 45: Part 8

RWS Diana 45: Part 8

by Tom Gaylord
Writing as B.B. Pelletier

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7

RWS Diana 45 air rifle
Diana 45 is a large breakbarrel spring rifle.

This report covers:

  • RWS Superdome pellets
  • Uh-oh!
  • RWS Hobby pellets
  • Air Arms Falcon pellets
  • Time to stop and think
  • H&N Baracuda Match pellets with 4.53mm head
  • Where we are

Today, we’ll look at the performance of the Diana 45 that we tuned recently. Although a new mainspring was installed, it has the same power as the spring that was in the rifle, so no vast power increase was anticipated. If there’s any increase at all, it will probably come from the new breech seal I installed. The old one was flat and hard, so the breech is probably sealing air better now.

The point of this tune was to eliminate as much vibration as we could. The rifle’s owner, Johnny Hill, did not like the buzz that came with every shot, and I told him that most or even all of that could be eliminated by tightening the tolerances inside the powerplant. At my request, he made a larger spring guide, and he buttoned the piston to take out as much vibration as possible.

Our plan worked to an extent because the rifle is now calmer, but some vibration still remains. I’ve never worked on a Diana 45 before, and this may be as good as it gets — or there may be some secrets about this model that I don’t know. This is as good as I’m able to make it shoot. I estimate that 75 percent of the previous vibration has gone away.

Now, let’s look at the velocity. The 3 pellets I tested this rifle with in Part 2 are the RWS Superdome, the RWS Hobby and the Air Arms Falcon. That’s where I’ll begin.

RWS Superdome pellets

First up are the Superdomes. When the rifle was still in factory trim in Part 3, they averaged 735 f.p.s. with an 18 f.p.s. spread. This time I got 870 f.p.s. on the first shot, but then the velocity started dropping off right away. By shot 14, the velocity was down to 803 f.p.s., where it seemed to be leveling off.

A second string of 10 shots produced an average velocity of 800 f.p.s. The high was 811 f.p.s., and the low was 787 f.p.s. That’s a spread of 24 f.p.s. I think the rifle is still breaking in and will shoot somewhat slower after a thousand shots, but it’s definitely faster than it was before the tuneup. However, there was an anomaly in this string.

At the average velocity of the second string, this pellet produces 11.8 foot-pounds of energy. I do think the average will be less after several hundred additional shots have been fired, but it’ll probably still be significantly faster than the 735 f.p.s. average before the tune.


In the middle of the second string, two shots went 509 f.p.s. and 524 f.p.s., respectively. Since the velocity on the very next shot was 804 f.p.s. and never again dropped lower than 787 f.p.s., I eliminated those 2 shots from the string and fired 2 more shots to replace them. But they did give me cause to wonder what was happening.

RWS Hobby pellets

The second pellet I tried was the 7-grain RWS Hobby. Before the tune, Hobbys were averaging 793 f.p.s. with a 28 f.p.s. velocity spread. Now they averaged 890 f.p.s. with a spread of 20 f.p.s. spread from 881 to 901 f.p.s. At the average velocity, Hobbys produce 14.6 foot-pounds of energy at the muzzle.

But there was another single anomalous slow shot in the string that went only 603 f.p.s. I excluded it from the string like before, but now I was really starting to wonder what was happening! I didn’t think it was the chronograph’s fault, though that is something I will have to look into.

Before I move on I would like to take a moment to reflect on what this rifle is doing. The Diana 45 is one of the original Four Horsemen of the 1970s. They were the first 4 to break the 800 f.p.s.”barrier,” ushering in the era of magnum spring-piston air rifles. Back then, the Diana 45 was advertised as getting just over 800 f.p.s. and could possibly be tuned to get up to 860 f.p.s. So, the fact that this one has just averaged 890 f.p.s. makes me feel a little proud. It probably won’t last, but it’s nice to know I can do it. And, yes, I know they probably didn’t have Hobby pellets to use for testing in the 1970s, but we don’t have to go there — do we?

Air Arms Falcon pellets

Next up was the Air Arms Falcon pellet. The first shot went out at 816 f.p.s.; and after that, none of the next 6 shots went faster than 448 f.p.s. I didn’t record a string because I felt this wasn’t the right pellet for this rifle as it is now tuned.

Time to stop and think

These slow shots were beginning to concern me. Especially when I shots 6 Falcons in a row in the 400s. Was the rifle somehow failing? It felt the same every time it shot, but the numbers were telling a different story.

I thought the Falcon pellets that loaded into the breech very easily weren’t resisting the piston with enough force. Perhaps, the pellets were moving before the piston slammed home and not allowing the air pressure to build up. The lighter Hobby didn’t seem to have the same problem, except just one time. And the Hobby fit the breech much tighter.

So I decided to try a pellet that I knew would give a lot of resistance. The H&N Baracuda Match pellet with a 4.53mm head is both fat and heavy. That would surely give the piston all the resistance required.

H&N Baracuda Match pellets with 4.53mm head

Ten shots with H&N Baracuda Match pellets with 4.53mm heads gave me an average 676 f.p.s from the Diana with a 46 f.p.s. spread from 658 to 704 f.p.s. There wasn’t a single slow shot in this string. At the average velocity, this 10.65-grain pellet produced 10.81 foot-pounds of energy at the muzzle. By the way, the average for this pellet (676 f.p.s.) is very close to the “magic” velocity of 671 f.p.s., which is the speed at which the weight of the pellet in grains equals the muzzle energy in foot pounds.

Where we are

We now have a tuned rifle that’s ready for one last accuracy test. That will be done at 25 yards with a scoped gun. Unless something odd happens, I’ll pronounce the rifle finished and return it to its owner with a couple recommended pellets.

For kicks, I might chronograph the accurate pellets after the accuracy test — just to see if I still get a slow shot now and then. If I still do, and the pellets that do it are accurate at 25 yards, I need to look at the chronograph. Velocities can’t drop by 200 f.p.s. and not affect where the pellets land at 25 yards.

I haven’t told you yet, but this test was the first one conducted using the new chronograph Pyramyd AIR sent to replace the Alpha model I shot up last week with the Benjamin Bulldog. This one is an Alpha Master that has a removable display and controller with an 18-foot cord, so now I can set the chronograph out on the range and operate it from safety. I’ll report on this chronograph after I gain some experience using it.

author avatar
Tom Gaylord (B.B. Pelletier)
Tom Gaylord, also known as B.B. Pelletier, provides expert insights to airgunners all over the world on behalf of Pyramyd AIR. He has earned the title The Godfather of Airguns™ for his contributions to the industry, spending many years with AirForce Airguns and starting magazines dedicated to the sport such as Airgun Illustrated.

40 thoughts on “RWS Diana 45: Part 8”

  1. Hi BB and the gang. Have a short question. I just received another Umarex pistol from Pyramid Air. It is the Colt Commander. There was a lot of drag inserting the magazine. I just got 4 reliable shots out of it and it exhausted all the C02 and the slide locked closed. 60 years ago I knew how to field strip a 1911 but believe it or not, I forgot. Anyway a internet search told me how to field strip it and found several jammed BBs. I lubed the slide channels, the magazine outer shell and the bb follower. I know the trouble resulted from the magazine not being properly inserted.
    Finally the question. Would have Pyramid Air’s 10 for $10.00 kept me from receiving that pistol with the ultra tight slide ? The pistol itself is very nice and compliments my blow back P09. One other comment, It would almost be worth the ten bucks to have a tech open up that darn blister pack. Thank you

  2. B.B.,

    This is same chrony I have. I changed lighting and got much better results. It does seem “finicky” but I am still learning. I will say that I never got anything even close to 350fps spread. I would not think that would even be possible with any pellet. Looking forward to the rest of the test.


  3. B.B.,
    Thanks for Part 8 of this report. I find it interesting that a near 12 ft-lb gun is the “magnum” of the 80’s. I am wondering if you have noticed any difference in cocking effort or smoothness after the tune compared to before? Has Johnny Hill tried it out yet and, if so, does he notice a big improvement in the shot cycle? I am looking forward to the accuracy tests. My Diana 45 likes Crosman Premier 7.9’s in the box, H&N Field Target Trophies and Predator Polymags. I don’t have near the experience with other springer’s that you have but I find my Diana 45 to be very hold sensitive compared to my Diana 52. Do you find the hold sensitivity of that Diana 45 improved from the tune? Have fun shooting and thanks.

    • Tabrown,

      I mentioned the gun’s vibration has dropped by 75 percent. The cocking effort feels the same as before, but I will weigh it in the next report. Johnny has shot the gun and agrees that the vibration is reduced.

      I doubt the tune changed the hold sensitivity. But We will see.


  4. AA Falcons shoot terrible in my 45 rifle and buzzy. they are excellent in the hw 35
    My rifle excels with premiers rws domes and hn ftt. It gets around 11 fpe but after shooting the tuned rifles I own, it’s like a buzzomatic. I think it’s enough to rattle the little Bushnell scope around off adjustment. Last shoot I could not get it to hit my swinging target at 25 yds.
    Would be a total package if the buzz could be gotten rid of.

  5. A vibrating rifle is something I cannot abide and fortunately have never experienced. I wonder if it would be worthwhile to attach armor plate to a chronograph. 1/8 inch steel plate should protect the mechanism, and fragile apparatus that extends out could be replaced.

    Among all the AR lovers out there, does anyone own a Ruger SR 556? Any opinion about it?


    • Matt61,

      I just made a 1/8″ alum. “shield” for mine. It copies the case in design, but no sides. I drilled a hole in the bottom to attach to the tri-pod along with the chrony. Did have to replace the tri-pod screw with a 1/4-20 bolt, as it was too short with the added thickness of the aluminum shield. (chrony is remote read)

      I also bought some 1/8″ Poplar wood dowel rods, but are too flimsy to support the sun screens well. They do work for break-away aiming guides though. BBQ skewers will work also but are much stiffer and a bit shorter. 16″ for dowels and stock steel rods vs 12″ for BBQ skewers, so the sunscreens will only work with the steel rods.

      As an “alignment guide”, I found that those fiberglass driveway marker rods that are 5/16″x48″ work well. Stiffer than wood and will not warp.


  6. Hi guys…

    something strange happened today.

    I cocked my Diana 31 and noticed a grinding sound. When I removed the stock I noticed that the spring was broken close to the front of the piston.

    This is especially weird since I’m using the German (F) spring that develops around 575 fps of velocity which is fairly gentle for an adult-sized rifle such as the 31. At that power level, the spring should basically last forever.

    I still have the stronger spring lying around, but the rifle is just too loud with it. I shoot in the attic and the shots make my ears ring and I don’t feel like wearing hearing protection. Apart from that, it’s also illegal, but who’s gonna complain 🙂

    I’ve sent an email to the dealer (the rifle is less than a year old)… I guess if I have to send the rifle in, I’ll rather pay for the spring myself…

    Kind regards,

    • Stephan,

      It is weird, but Diana mainsprings have always been a little too hard for their own good. That makes them brittle. And I don’t know if they shot-peen them to relieve the stress. So they have the reputation for breaks off one inch from either end and coiling up inside the remaining spring. The gun becomes easier to cock and smoother shooting, but that is the high-powered model I’m referring to. The lighter spring might just get in its own way during cocking.


  7. BB,

    You had as similar speed problem with a Beeman RS1000H Dual-caliber rifle combo (post March 12, 2008). Maybe this is more common than just this rifle.

    Does any of the other readers have experienced these speed drops?

    If I may propose a subject for a blog: The long term storage of airguns. I need to store guns for 9 months at least in a cabin which can be humid but also quite hot. What is the best way to preserve them?



    • August,

      Try searching VCI plastic and paper. I believe it is a product that is impregnated with a gas that prevents rust and corrosion. We use it at work when sending very expensive electronic switchgear overseas. GE requires it.


    • August,
      Go online and check out Boeshield T-9, it is a thin liquid which dries to a waxy film which can be readily removed when necessary, it is available in liquid or aerosol. I do not know if it would be detrimental to the finish on a gun stock.


  8. B.B.,

    With the 15.89’s re-tested, and 1 other type done, 5 types to go,….what is the chrony data that you would like to see?

    High, Low, Spread, Average, Standard Deviation and (Pellet type and Weight) ??? Might be a week or even 2, but I wanted to know what was most usefull to you.

    Thanks, Chris

    • Chris,

      As the data accumulates, look at it and see what it tells you. That is what everyone wants to know. Too many numbers will put the readers to sleep. Look for the interesting trends ort deviations and tell us about them.

      For example, as you shoot, are the strings getting tighter? That is of interest either way.


      • B.B.,

        Thank you for that advice. I have had plenty of thoughts on “trends” and “deviations”,.. asking myself,..why? I have shot enough to have come across a “few”.

        Another words, save the “hard data” for when there is a problem…..

        On a side note,…in today’s report, you mentioned “magic” when referring to the pellet weight/muzzle energy. I remember reading this before, but never gave it much thought.

        What is “magic”, other than the coincidence of #’s? Or,…does it mean something with regards to some optimum speed or a ballistic/accuracy formula?

        Maybe you have covered this before, but you said it today without an explanation to the word “magic”,…so I just got to ask.

        Thanks, Chris

        • Chris,

          I referred to the “magic” number for velocity — 671 f.p.s. That is the speed at which the weight of the pellet in grains equals the energy of the pellet in foot-pounds. So if someone tells you his rifle shoots a 10.5-grain p-ellet at 671 f.p.s., you know without calculation that it produces 10.5 foot-pounds at the muzzle.

          Knowing this relationship allows you to make close estimates of the power of an airgun. For example, if someone tells you his rifle is shooting a 15-grain pellet at 700 f.p.s., you know that it produces more than 15 foot-pounds.

          There is no magic — which is why I put quotation marks around the word. That is a typographical way of saying, “This isn’t true.” or “This is not the case.”


          • B.B.,

            Thank you for that explanation. I did not know that or remember reading that.

            With just getting a chrony, I still have yet to get into all the calculations that relate to ballistics.

            Maybe an idea for a topic…..a “in a nut shell” report into ballistic calculations.


  9. BB,

    you nailed it 🙂

    “So they have the reputation for breaks off one inch from either end and coiling up inside the remaining spring.”

    That is *exactly* what happened…

    The rifle could still be cocked, but made crunching sounds. Firing didn’t seem that different.

    Even more strangely, I’ve shot a quick group with the 1000fps spring and Geco pellets and it wasn’t half bad. It seems it doesn’t actually become a lot more difficult to shoot (but the noise is annoying 🙂

    • Stephan,

      Those two smilies tell me your delight in discovering a fundamental truth. I love it when I learn things like that!

      Now — what to do? Maybe go in a different direction? Maybe replace the spring with one not made by Diana? Maybe an aftermarket spring that is advertised for its strength, rather than power? The Brits have a lot of stuff like that.


      • BB,

        I’m not 100% sure I know what you’re getting at… What’s the fundamental truth you’re referring to?

        I noticed I don’t need magnum power a while ago. That’s why I was using the weaker spring.

        The first smiley was because I was surprised that you accurately described what had happened. You must have seen a lot of these cases.

        I used the second 🙂 because most people seem to think power is really important but I noticed that it’s mostly annoying to me. I’m now somewhat beyong the “blowing stuff to bits” phase and rather have a calm and quiet gun.

        The firing behaviour was actually quite ok with the 575fps spring. I may have noticed some buzz and decrease in accuracy recently. I wonder if a spring failure can happen gradually. The spring doesn’t look bent.

        I read a lot of reviews and I haven’t come across many complaints about Diana spring failures.

        Some people have mentioned that they break a mainspring in their HW45s every 10.000 shots though, while others never had this problem. We’ll see whether that happens to me. In any event, I guess the HW45’s spring has to work much harder, generating all that power from a small powerplant… The Diana has a much larger compression chamber and longer spring and isn’t all that much more powerful in the German standard configuration. The spring should have it easy 🙂


  10. BB
    I believe your few low velocities are from exactly what you said with the lighter pellets verse’s the heavier pellets.

    I think the heavier pellets allow the air to hit the skirt and seal it to the barrel before the pellet moves.

    And I bet that’s more common with a leather seal verse’s a synthetic seal also.

    Just thought I would pop in and add my two cents worth. Still in crazy mode with the move thing. Man its amazing the stuff that we collected over the last 5 years or so.

  11. B.B.,

    Aside from the above question, “magic”,…..I wanted to say that the Alpha seems (VERY sensitive to keeping the shot very straight over the sensors). This is at only 2~3″ above the sensors. I got error2 several times yesterday and a couple of times today, even with laying the dowel on the barrel to check alignment through the chrony. I finally ended up “eyeing it” and it worked good. Muzzle 3′ away from 1st eye.

    The pellets today shot a 7.38 spread which is pretty good, ..I think?

    I am looking forward to your report on your new chrony.


    • Chris,

      If you shot 10 pellets that only varied by 7 f.p.s. then your gun is shooting very consistently.

      I would stop using the velocity decimals. Round off the number and things will make more sense to everyone, including you!


      • B.B.,

        Without getting into #’s too deep, the other 2 types I shot had a (spread) of 21fps and 17fps.

        The 17fps was with the 15.89 JSB that previosly got a 65 fps spread,….(before) the lighting change. Like I said, the Alpha seems to like a low shot and very straight over the eyes. At least mine anyways.

        Will be switching to the 500 watt Halogen instead of the 2….100 watt currently in use.

  12. B.B.
    I’m confused! Is the occasional “slow flyer” because of a bad chronograph, bad gun, bad pellets? Is the barrel choked, would this make a difference? Is the feel of the firing cycle noticeably different of one of the subpar shots?
    Will you reveal a solution in part 9?


    • Yogi,

      I’m confused, too. I really don’t know what causes that, but I am working on finding out. I started by using tight, heavy pellets that seemed to make it go away. I will watch the new chronograph, as well.

      Maybe after accuracy testing I will chronograph the rifle again and see how it does.


      • B.B.,

        An easy solution to find if your chrony is working properly is to shoot at a target while shooting over the chrony. A large deviation in your shot string that doesn’t show up on your target ….. well, you get it.

        David H

      • B.B.

        David H makes a good point, I would like to add do you still have that Oehler chrony? Perhaps set it up so you could shoot thru that and the Alpha at the same time.

        That would tell the tale for sure.


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