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Accessories Diana 34 Easy Modular System (EMS) Synthetic: Part 7

Diana 34 Easy Modular System (EMS) Synthetic: Part 7

Diana 34 EMS
Diana 34 EMS with synthetic stock.

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

This report covers:

  • RWS Hobby
  • Discharge sound
  • Air Arms Falcon
  • Norma Golden Trophy
  • Cocking effort
  • Trigger pull
  • The trigger
  • Shot cycle
  • The accuracy test
  • ASP20?
  • Summary

Today we look at the velocity of the Diana 34 EMS with the Vortek Diana 34 EMS gas spring conversion kit installed. I used three of the same pellets that were used to test the factory 34 EMS with its coiled mainspring, back in March of 2021, so we will have a direct comparison between the coiled steel mainspring and this gas spring. Let’s begin.

RWS Hobby

The coil spring developed an average 927 f.p.s. with the RWS Hobby pellet. It had a spread of 18 f.p.s.

The Vortek gas spring developed an average 1025 f.p.s. — a 98 f.p.s. increase in velocity. The low was 1021 and the high was 1030 f.p.s., so a 9 f.p.s. spread. At the average velocity this pellet produces 16.33 foot pounds of energy at the muzzle

Discharge sound

The discharge sound is a healthy 109 dB. With the coil spring it was 101.3 dB, so the gas spring did add to the noise. None of the pellets broke the sound barrier, so the noise was all in the powerplant.

EMS discharge

Air Arms Falcon

The second pellet tested was the Air Arms Falcon dome. With the coil spring this pellet averaged 919 f.p.s. with a spread of 49 f.p.s.

With the Vortek gas spring this same pellet averaged 1002 f.p.s. That’s an increase of 83 f.p.s. The low was 998 and the high was 1007 f.p.s. for a spread of 9 f.p.s. At the average velocity this pellet produces 16.35 foot pounds of energy at the muzzle.

Norma Golden Trophy

The final pellet I tested was the 8.4-grain Norma Golden Trophy. With the coil spring that pellet averages 835 f.p.s. with a spread of 17 f.p.s.

With the Vortek gas spring this same pellet averages 917 f.p.s. — an 82 f.p.s. gain over the coil spring. The low was 912 and the high was 921 f.p.s. — a difference of 9 f.p.s. At the average velocity this pellet produces 15.69 foot pounds of energy at the muzzle.

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Cocking effort

With the Vortek gas spring installed the rifle cocks with 35 pounds of effort. Compare that to 29 pounds the coiled steel spring takes after a small break-in. I guessed the gas-spring cocking was 28-29 pounds because it is so smooth, but the coiled mainspring also cocked very smooth. I actually thought the gas spring cocked easier than the coiled spring, so the smoothness really confused me.

Trigger pull

The previous test of the two-stage trigger netted 11 ounces for stage one and 18 ounces for the release at the end of stage two. Today the trigger tested 12 ounces for stage one and 17 ounces for the stage two sear release. That’s too close to call. I say the trigger hasn’t changed.

The trigger

In Part 6 reader gnom256 chastised me about my installation of the Vortek gas spring where I left the original Diana steel bushing out of the trigger assembly.

Hi, Tom!Original trigger bushing is strictly necessary for correct trigger operation! You should to get it back as soon as possible!

The specified pressure is much higher than the permissible one too.”

So I called Tom Gore who had already assured me that the picture I showed you of his unit attached to the 34 EMS trigger was correct. Tom said:

This trigger is not a T06 trigger. It  is a T06 that has been modified to accept an N-TEC gas spring that Diana never produced for the 34 EMS. I showed them my unit and Diana engineers have blessed it as correct for the 34 EMS trigger.

Diana 34EMS Vortek spring installed
This picture shows the Vortek gas spring correctly installed to the Diana 34 EMS trigger assembly — per Vortek and Diana.

Shot cycle

The 34 EMS now shoots dead smooth. There is a pulse but until I test the accuracy I can’t say more than that. 

The accuracy test

I’m going to hold off shooting for accuracy until Vortek sends me one of their new barrels. The EMS is a modular system and a barrel swap is supposed to be part of the deal. Vortek will now make this possible. If I test the accuracy with the factory barrel I’m not doing anything I didn’t already do in Parts 3, 4 and 5, back in 2021.


I said in Part 6 that this gas spring conversion could be a complete replacement for the Sig ASP20 air rifle that’s no longer available. Today’s test shows that the power of this unit falls short of the ASP20 power. I don’t own a .177-caliber ASP20 to test for velocity, but the number 20 in the title indicates that in .177 caliber that rifle gets 20 foot pounds of energy. The 34 EMS has hit just below the mid-16 foot-pound range. As far as accuracy goes, we will have to wait for that test. And remember, this kit is available right now.


The Vortek Diana 34 EMS gas spring conversion has now been installed and tested for velocity in my .177-caliber 34 EMS. It installs easily and the velocity is a sharp increase over the factory mainspring, with a corresponding sharp increase in consistency.

41 thoughts on “Diana 34 Easy Modular System (EMS) Synthetic: Part 7”

  1. Everyone,

    What’s the matter? Cat got your tongues? 😉

    I thought there would be HUGE response to this post. A modular spring-piston air rifle that you can change calibers and power levels — what’s not to like?


    • B.B.

      I think your reader drank to much egg nog! Perhaps they are fatigued by all shopping and bills they are accumulating….
      I would think that this EMS with the gas ram might shoot better in .22 caliber. 1,000 fps is pretty fast for a little old .177 pellet. Maybe a .177 slug would work well?

      The trigger in my Diana 340 N-Tec is called a “modified T06 trigger”. I never have been inside the gun so I do not know exactly what it latches onto. While not the best trigger, I do know exactly when it will fire.

      I wonder if the swap of powerplants on the SIG ASP20 will be as simple? The Diana was designed to be modular, the SIG was designed to keep people from tearing into it.

      Perhaps at some time Tom from Vortek could write a guest blog about the complexity differences in designing and building both a fixed pressure gas and an adjustable gas ram? I would image that the differences are HUGE.

      Also, do you know if Tom’s gas ram will fit my 340 N-Tec?


      • Yogi,

        I just ordered some .177 slugs for testing guns like this, so we shall see.

        I have forwarded a link to this report to Tom Gore and he does read the comments. As far as the 340 N-Tec, I’m pretty sure this gas spring won’t work in it, but if Tom tells me different I’ll get back to you.

        As for the ASP20, Tom is going to look at mine to see what can be done — if anything.


    • With reduced spreads, I think another accuracy test with the same barrel will be worthwhile. Heck even the norma pellets may finally found a compatible airgun. Plus adding a few slugs to the mix would be informative.

      I have always been interested in the possibilities of this rifle, but disappointed in the lack of available modular parts. Here’s hoping that Vortek is successful.

    • B.B. Pelletier,

      no chance !
      My ‘Chief Security Officer’ would have prevented such, see picture… 🙂

      I read your article first thing this morning. And then the internet went down. 🙁

      I suspect that the horizontal rain may have had something to do with that, you see, here, in my part of France, the electricity- and phone lines are all above ground. Many of the wonky pylons are loose, partially- or completely missing, etc and I think that makes cables vulnerable during strong’ish winds.

      Anyway, that’s my excuse ! 🙂

      My gas-ram powered SigSauer Asp20, bought from Germany, bears an F in pentagon and yet shoots with surprising authority.

      (ASP20 shot over chronograph – 121MB/68s long video : https://drive.proton.me/urls/7DNWPKSWQ0#rOVcMU7GO1kJ )

  2. Tom,

    The Vortek gas is shown by your tests to be very consistent in producing power and giving smoothness in cocking enough to fool you thinking it required less than the actual force to cock it. I think Vortek has a winner in their hands, That consistency will hopefully translate into better accuracy in the succeeding tests. I do begin to wonder what the difference in swept volume of the Diana 34 EMS is against the Sig ASP20 which could be how the ASP20 produced more power with the same cocking effort.

    Is it safe to assume that reader gnom256 is somebody testing the waters for the blog as a Trojan Horse for malware?


      • Yogi,

        I have a sophisticated program on my computer that watches for such things. Just the other day I went to a page that had 44 malware hacks that were caught.

        I won’t name the software I have because that would just give hackers more imformation to bypass it.


        • B.B. Pelletier,

          thank you for raising the alarm !

          Although my ipad is still fine with gnom256’s website (Internet Service Provider is Orange France, which I connect to via Wi-Fi and a Virtual Private Network, currently through Holland), I appreciate that you care enough to have warned us of the potential danger.
          Thanks again.

  3. A significant increase in velocity and smoothness. Sounds good to me. But I have been reading about ballistics of diabolo pellets and how they are aerodynamically more stable than typical bullet shapes, etc. The different types of barrel rifling that are used is an interesting subject also. Anyway, what is your experience on how increased velocity affects accuracy? I would guess that it would vary with various pellets. Have you tested that aspect in the past and concluded anything?

    • Elmer Fudd,

      I will grant you that Pellets often are more stable at short ranges (under 50 yards when compared to bullets (in recent past and most current airgun slugs) because of barrel twist/MV mismatch.
      Also most shooters have NO conception of bullet to barrel sizing being at least an order of magnitude more important than with pellets designed to have their skirts blown out to engage the rifled bore.

      What is/are: “…typical bullet shapes, …”


      • It is fascinating to me to read about these things. As I understand it:

        Bullets come in various shapes of course. One of the most stable bullets is the ammo that Oswald used in the assassination of JFK. It has a round (domed) shaped nose with long straight sides. If I remember correctly, the rifling in the barrel is progressive (meaning that it increases as the bullet nears the muzzle). The straight sides of the bullet create more contact surface area (than say a pointed-nosed bullet) between the bullet and the rifling. This all serves to impart higher spin to the bullet. And the spin of the bullet is what affects its stability the most.
        Conversely, the diabolo pellet depends more on its aerodynamic shape combined with its center of gravity typically being forward of its (aerodynamic) center of pressure. Bullets usually have their center of gravity to the rear of the (aerodynamic) center of pressure. The distance between the two centers (gravity and pressure) creates a moment (or lever) that helps the aerodynamic force (some say drag, others say lift) of the flared tail of the pellet correct any yaw that the pellet may have at any point in time. A bullet on the other hand, with it’s center of gravity behind the center of pressure (and no flared tail), has less stability (ability to correct any yaw) it may have at any point in time.
        Reading about the physics is one thing, but I thought BB, and some others here, would have some practical experience. So I asked and was impressed with the response.

        • Elmer Fudd,

          If you haven’t read this guys stuff already you might enjoy doing so.
          I have posted this Link any number of time in the past.

          One item i noted in your post: “The straight sides of the bullet create more contact surface area (than say a pointed-nosed bullet) between the bullet and the rifling. This all serves to impart higher spin to the bullet. And the spin of the bullet is what affects its stability the most.”
          The only things that directly effect rate of spin in a proper fitted projectile are the Twist Ratio and Final Barrel Velocity.
          A Progressive rifled barrel is no different to a continuous twist ratio barrel. The Final Barrel Twist Ratio and MV is what determines rotations per unit time.


          • Thanks, that looks like a lot of good stuff. I agree with what you said. A couple of more things I should have said about the JFK assassination ammo: It is a full metal jacket bullet, so it is a much harder material than relatively softer lead, contacting the rifling. And the long straight sides should help keep the bullet more stable (than a more pointed bullet) while it is still in the barrel. So it should be more stable as it leaves the barrel.

  4. Hope something can be done to repair your ASP20, Tom. FM was always wary about SIG’s “no spare parts, no DIY” approach to marketing this rifle; that’s a red flag, as in “beware, we have no plans to manufacture and/or support this for long.”

  5. BB,

    If this gas spring and barrel conversion turns out to be a good one, it fulfills all of the promises of the big-box store rifles (that they never seem to attain). Smooth operation, power, good trigger and accuracy(?). If so, it shows what can be done.
    If only the manufacturers would take note. It seems too easy to make things that miss the mark, but very few seem to find the right recipe (Weihrauch seems to do well, more often than not).
    Keep up the good work, as you know that there are some people listening out there.


  6. B.B., Yogi, and Readrship,

    Yogi wrote: “I wonder if the swap of powerplants on the SIG ASP20 will be as simple? The Diana was designed to be modular, the SIG was designed to keep people from tearing into it.”
    What did he base his comment on?

    Are most Coil/Gas Spring break barrel airguns easy to work on BY DESIGN?

    This DARK SIDE DEVOTE doesn’t know because other than removing the action from the stock to have a cursory look around i have had NO NEED to dive in; since both (.177 & .22 caliber) SIG SSG ASP20s continue to shoot to specifications or BETTER.
    They didn’t look more complex than most of the airguns Tom and others have gone inside on. SIG just didn’t supply parts for consumers.
    WHY! Please tell me (perhaps others too) if you know for a valid reason [ONLY] to disassemble a working accurate shooter by a regular owner, please.

    Would I go into a gun that shoots well with no OEM or TRUSTED aftermarket parts available to me?

    NO, just that simple.

    For Tom: i don’t own/have any of the pellets you used in your testing above. I might order some of them (next time i order pellets) for my .177 and then provide my Labradar results.
    Anecdotally (based on R-10s) the .177 SIG will probably, at minimum, go TRANSONIC+ with some of those pellets.


    • Shootski

      I can confirm your suspicion. I shot one and only one R10 pellet 7.0 gr in my ASP20. The report was similar to a .22 Long Rifle cartridge shot in a pistol. I don’t know if that correlates to a seal failure over a year later which Sig repaired.

      Readers should know this is not a knock on the R10 pellets. They are a favorite choice for accuracy in two single stroke guns I shoot.


      • Decksniper,

        I was actually referring to the 8.2gr…7gr. would certainly go supersonic just like you found out with your ASP20.
        I doubt your seal failure was caused by the R-10 pistol 7gr. Pellet. No expert but logic says the Mass difference is not going to cause a failure especially one that takes a year to present.
        With the JSB Knock Out in .177 the 13.43gr. were not as accurate beyond about 40yards as the 10.03gr. Slugs.


        • Shootski

          “With the JSB Knock Out in .177 the 13.43gr. were not as accurate beyond about 40yards as the 10.03gr. Slugs.”

          Thanks for this tip. I will make myself a note if I ever decide to shoot slugs in my ASP20. I remain overly cautious about messing with my Sig repaired rifle.

          Merry Christmas


          • Decksniper,

            The .177 were probably more accurate inside 40 yards but by so small of an amount that it was not statistically significant. Given measurement error on top of that the choice only matters if you need the extra Mass for hunting.
            Part of me back then wanted to show that the folks who kept saying pellets were more accurate than bullets (slugs) were blowing smoke and get manufacturers work on bullet (slug)design to shoot better in airguns.
            Pellets are still less expensive just based on Lead (Pb) content.
            For huntes, given an airgun that can shoot them well, who are interested in better accuracy and humane harvesting at greater distances (especially in the WIND) there really isn’t a choice any longer.

            Wishing you and yours a Joyous Christmas and a Happy New Year!


  7. shootski,

    The trigger is only adjustable to a certain extent. In B.B.’s report, he mentioned the SIG did not want owners monkeying around inside the ASP20. Why do you think no OEM parts available? It immediately turned me off of the SIG.

    One reason to tear into an airgun is to change the piston seal. Smoothing the rough edges in the compression tube is another reason. Applying new and perhaps proper lubrication. Can you think of any others?

    • Yogi,

      Regular Owners….

      Also IF what Tom reported in his SIG visit is to be believed SIG already did that during the build.
      Most owners are NOT blessed with the skill set to find all the rough edges let alone smooth a compression tube’s rough edges IF there are any.

      Yogi, i can’t find any if there aren’t any thus far.

      Time will tell.

      Tom’s gas spring failure is either infant mortality related or a long no shoot interval related…per Ed Shultz’s reported advice on gas spring exercise needs that i have pointed out in various Reply on this Blog… ad nauseum.

      You don’t own one because you didn’t like it; great!
      Your loss in my opinion.


      PS: 50 yard bullet (Slugs) groups SPEAK…granted 5 shot.
      Photos posted in Reply to you above indicate some degree of inherent accuracy. I’ll reattach if posible for readers to evaluate for themselves.

  8. BB,

    I have to admit, those very low and consistent spread numbers gives this air rifle some hope of being fairly accurate. I also feel you should test this particular barrel again. I am looking forward to the new Vortek barrel for this kit.

    What I would like to see is for Tom to further pursue the adjustable gas sproing. That is something I would be most interested in, most especially if it is rebuildable.

    I do not care for the stock that is on this air rifle. Of course, you and everyone else knows how I feel about those glowy thingy sights. In the deep, dark recesses of my mind I seem to recall that these sights can be swapped out. The wood stock and swapping out the sights would make this more amicable for me. It is a shame the new owners did not take this idea to more of a fruition. Of course, this does open the door for people like Tom.

    I missed out on yesterday’s blog. Once upon a time you could get a decent sproinger for under $300. I am afraid that it will likely take someone from Wang Po Industries to do such these days. There are a couple of companies that are here or in Europe that could do it, but first they will have to work on their triggers a bit. I personally would like a nice shooting synthetic stock sproinger for under $300.

  9. “…the velocity is a sharp increase over the factory mainspring,
    with a corresponding sharp increase in consistency.”

    That’s all to the good, but the accuracy test will really tell the story.
    If it’s accurate with this power increase, then they’re really got something here. 🙂
    Blessed Christmas to you!

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