DISCLAIMER;

First of all, an apology. Steve and I started exchanging more and more information and I got carried away on a tangent. He was kind enough to "call me back on track". Perhaps I am too much of a scientist and love bare truth too much. So, I need to rely on good friends to make me see the forest, as I am too entangled in the trees; the delay is mine and mine alone.

What follows are my own personal observations, conclusions, and hopes of further work.
I take full responsibility for what I say or write. If someone demonstrates me that I am wrong, as I have done in the past, I will stand corrected.
Nobody's "Purfect".

Let's re-cap: the FOCUS of this series of articles was the Harmonics Tuner (HT); a relatively simple device that allows the shooter to tune a gun to the best possible performance of a given pellet in the gun, WITHOUT altering the MV.
​
The idea was to compare the performance of the HT under two completely different powerplants to see if there was ANY measureable improvement from both, as different as they are.
As you can see from the results, there is. Smaller or larger, but there is a measureable improvement.
This is what I feel is most original.
Typical airgun tuning is done through cutting coils, change of springs/guides, change of pellets, and adding or removing washers that go from full sized spacers to paper thin power adjusters. BUT that means altering the trajectory (because MV changes) so that accuracy can be obtained.
The HT, in a way and within reasonable limits, allows us to "have our cake and eat it too"; because we can select an MV (obviously within the stability range of the pellet we want to use, and assuming that the barrel does not deeply dislike the pellet), and THEN tune to optimal accuracy and precision (depending on what we want to do with the airgun) to the best possible results within that system.

I have also received "questions" about the validity of using 5 shot groups as "data points" being that sometimes variations between groups are as large without any change, as they are when performing small changes. As limited as our tests were, we are confident that the results are reproducible in any individual's airgun, as long as the proper procedures are followed. 
​The RESULTS for individual guns may be different (as is normal with most aspects in airgunning), but everyone can find an "optimum spot" for harmonics tuning.
​That is part of the essence of the beast.

So, having clarified all that, let's get going

We might make some tweaks still, as this is a pre-production model.
​We are working on making the HPM available as an after market part for ALL 54's (as usual, in good DIANA tradition, it will be fully compatible with all previous editions of the 54, though the T01's may need a little gunsmithing).
I am told that the stock will be available in several colors and that also more traditional Beech (and perhaps some Walnut) stocks will be made available. It all depends on the wholesalers, so if you are interested, write to your favourite wholesaler to request some attention to the point of your interest.

Steve and I have been exchanging a lot of interesting information, and I have also been receiving results from the Harmonics Expert, such as this:

So, I will be writing another entry, this one dedicated to a more detailed and better analysis of what TRULY happens with the spring-piston shot cycle, what determines the efficiency, what are common misconceptions about it, and analyzing more in depth the "phases" of the shot cycle.

Just to give you an advance taste:
The curve above belongs to an ASP 20
You can clearly see that the first acceleration spike (red oval) is where the piston reaches the end of the air compression run, and that a few msecs later (green oval) there is an even greater "slam" BUT, the human senses cannot detect it.
You can also see the 70 g's force vibrations developing during the time of the pellet in the barrel (-20 to +50 g's for 7 msecs, though the dwell time of the pellet in the barrel is shorter).

It takes relatively sophisticated instruments to detect and measure them, not only in magnitude, but also in time. The chart also shows a good, long decaying vibration pattern (blue square).
And all this from a gas spring gun that has been reported as a "smooth shooter" and excellent at bench rest.
¡Surprise!

Anyway, it will be fun to actually make the real behaviour of the shot cycle evident for different airguns. And to see what works and what does not work, independent of what shooters "feel".

Conclusions:

The HT is a device that has been tested and proven in different power plant designs and has proven its value.

​DIANA will include it in the next " edition" of D54 rifles.

There are still other technologies that await research; as long as there are people that are fascinated by the spring-piston airgun, whether it is a steel spring, or a gas ram, there will be things to discover and improve.
And THAT is also part of the magic of airgunning.

Again, I need to thank Steve for his excellent participation and impeccable work. It has been a great pleasure working with him on this.
And also thanks to our readers because without dedicated airgunners willing to read a LONG, FOUR part, entry our words would be like the sound of a tree that falls in the middle of an empty forest . . .

Keep well and shoot straight!






​HM

N.E.
For those of us that remember B&W TV, "B" Westerns, and were raised on a visual diet of clear-cut good and evil as white hats and black hats, the name 'Dragnet' will always recall Det. Sgt. Joe Friday.
And badge # 714 will always mean dedication to the truth and unswerving loyalty to the Law.
Among its most famous phrases:
"All we want are the facts, Ma'am"
In honor of such a simple, unswerving, and devoted to service attitude, we decided to title this entry.
​
Take it away, Steve!
​

​As promised, I wanted to provide you with more in depth detail and comparisons between the two power plants that were used in the recent Harmonic Tuner testing.  

I mentioned in that write-up that after recrowning the barrel on my 56TH, Hector completely assembled my barreled action with some of his own components and returned to me for  testing.  It arrived with one of Hector's Short Stroked HMO powerplants, a tuned T06 trigger and the most beautifully detailed Diana 54 stocks I have ever seen! He went all out on this set up provided to me for testing.

We have already seen the rifle in action during the Harmonic Tuner testing.  Now lets turn our attention to the powerplants,  beginning with the Short Stroke HMO set-up.

28mm x 76mm HMO Short Stroke

The set-up as provided to me included everything you see pictured below;

Compression Tube with Reinforced Breech Seal
HMO piston
Main Spring with dual guides
Cocking Handle with modified fulcrum and linkage extension

It was set up for my requested energy level (11.2 to 11.4 fpe range)

​The HMO piston is a work of art with an o-ring main seal, nylon top cap, and a rear guide that is nicely machined to ride solidly inside the action, an improvement to the flared out piston skirt on factory pistons. 

You can also see the dual spring guide set-up.  This includes a conventional guide that inserts into the main spring, and an outer guide that surrounds the spring.

​Looking at the Transfer Port you can see the seal has a center reinforcement collar measuring approximately 3mm ID.

​The piston weighs in at about 317 grams.

​Inside the outer spring guide are the preload spacers, one of which appears to be a softer compound anti-bounce washer.  It is the blue washer in the picture below.

​I mentioned the "Modified Fulcrum" on the cocking handle.  Here is a close-up showing the re-positioned cocking linkage pin.

​The linkage rod end is solidly supported with nylon washers on either side for a smooth cocking stroke.

​To account for the relocated pivot point, the linkage rod has a threaded extension added.  In this picture you can see a factory linkage rod (bottom), alongside of the modified cocking linkage (top)

​It is evident that Hector has done his homework on this set-up.  It is precise, consistent and was easily tuned on target using the harmonic Tuner.  The cocking stroke is extremely light and will have you questioning whether or not your are truly making over 11fpe.

After all testing was complete, I purchased this set-up from Hector.  It is well made, durable and easy to tune on target.  I was able to successfully tune to sub 3/16" c-t-c 5-shot groups across two series of tests at 32 yards.
​
AGT 22mm x 96MM Skirtless

This set-up has been covered in much greater detail in a couple posts I have made on GTA and AGN, but I will give a quick overview;

This set-up consists of a factory Compression Tube sleeved down to 22mm.  The transfer port retains the factory 4.1mm ID.

The piston uses the factory piston rod, and has a dual seal piston affixed on the end.  The dual seals consist of a parachute seal and an o-ring main seal, and help reduce the effects of temperature changes on your velocities.  The piston also has two supporting guide bearings, with a special top hat that also functions as a third support bearing.

This is an exceptionally smooth powerplant and was producing groups as small as 1/4" c-t-c at 49 yards.  It is also very well made, solid and durable.  Adjusting preload can be done without a compressor.  I am able to compress the trigger assembly into place with one hand and insert the trigger block pins with the other hand.

​This piston weighs in at 149.5 grams

​In addition to the mechanical and dimensional comparisons, I also set up a test to measure the cocking effort for each set-up.  

This was accomplished by taping a Protractor above the Cocking Handle, centered directly over the pivot point.  The rubber grip cap was removed from the cocking handle and a slotted wooden block was inserted inside the end of the handle.  The block was supported by rubber sheeting, and had a groove in the center.  I then looped a wire tie around the handle, centered in the groove.  The rifle was supported firmly in a padded support and measurements were taken using a digital scale. 

The weight measurements were taken at specific locations in the cocking stroke, with the max reading being recorded just before the piston rod contacted the trigger mechanism.  Due to the differences in cocking stroke length across the power plants, the max readings were not the same as you can see in the chart below.

The pull point was centered right where you would place your hand when cocking the rifle and scale was kept inline with the direction of pull.

Here is the set-up for testing:

With the barrel crown issue now resolved, we moved to the next step in this project which was the HT (Harmonics Tuner) installation and testing.  

With the rifle set up, Hector conducted his own series of tests just to verify what setting it would prefer on target.  Once complete, he reached out to me to see if I would be willing to continue with this testing.  Hector said that he would like to keep the rifle set up just the way he had it for my first phase of testing.  After discussing the terms of this testing I agreed without any hesitation.

A few days later the rifle arrived.  For this testing you would think that the equipment would consist of an old beat up stock and parts that were laying around in Hector's shop.  After all, it would be packaged and shipped to my shop, plus be assembled and adjusted throughout the testing, and finally disassembled packaged and shipped back to Hector.  

Much to my surprise when I received the package, I found an exceptionally well packed rifle in a padded hard case, with precisely cut out areas for each item.

Included were a Vortex 6-24x50 Diamondback Tactical, a custom parallax adjustment wheel, an accurized ZR mount, and the most beautifully detailed D54 stock I have ever seen.  Wrapped over the stock was a padded leather cheek piece...very nice!  

​Inside the back it looks like a nylon collar machined for an exact flush fit to the end of the muzzle with zero o-rings added

​Adjustments are made by adding or removing o-rings.  Adjustment range is between 0 and 10 o-rings.  Simply loosen the 3 set screws, slide the HT off, add/remove o-rings, reinstall HT and lightly snug the set screws.

​Here is a view from the front of the HT.  I think this picture was taken with 9 o-rings installed.

Now let's talk about the arrows:
​While I was doing this chart I saw a pattern to both tests that I did not notice before.  Both tests have a sort of rolling pattern to them where the groups gradually increase, then decrease in size, and then start over again.  Look attentively at the arrows in the chart above.

Ignoring the normal group to group variation that you would expect to see when shooting consecutive groups without making any changes, you can definitely see these patterns.

It looks like the 28mm set-up has a more pronounced climb from smallest to largest group sizes, and the 22mm has a less pronounced climb.  This was reflected in my article and supported by the data.  However, in the 0-10 o-ring range of testing, the 22mm had three cycles of this pattern, while the 28mm had only two.  In my opinion this supports the theory of increased frequencies being produced by the 22 mm's kits. 

The 28mm generates higher harmonics (as shown in the greater spreads from smallest to largest group sizes), but lower frequency (only 2 complete cycles of small to large groups in this testing)

The 22mm on the other hand made three complete cycles in this testing, indicating higher frequency.  The peaks and valleys (group size differences) were lower so the harmonics were not as pronounced, but it occurred more frequently.

So, looking at this chart, I would bet that the targeted ranges for o-ring settings should be similar if you target the valleys (smallest groupings).

For example, on the 28mm the best settings could be either 0 o-rings or 9 O-rings (at this exact set-up, velocity, pellet, etc).  A slight change to the set-up would require a new test, but results should be similar with 2 specific settings being revealed in the range of 0-10 O-rings.

On the 22mm set-up, you should find 3 valleys across the range of 0-10 O-rings due to the increased frequency of the harmonics.

This is VERY interesting!!  I am theorizing that tighter groups in both tests would relate to the barrel being tuned to match an end point of muzzle movement with the release of the pellet.

​Testing summary;

28mm x 76mm HMO Short Stroke

The HT was very effective in tuning the 28mm x 76mm short stroked powerplant. You could see dramatic changes in group size with even the slightest change in HT settings.  The size difference between the largest and smallest group was .512".  
You could also clearly see when you were in the sweet spot ranges for the tuning (1-4 o-rings, and 8-10 o-rings).  This powerplant did not like the range of 5-7 o-rings.  This would be in direct relation to the barrel harmonics when using this particular powerplant, and at this particular power setting.

AGT 22mm x 96mm Skirtless

While I could see slight changes across the adjustment range of the HT, the overall effects of the adjustments were less.  There is no doubt that a sweet spot could be found for dialing in for the smallest group, but the size difference between the largest and smallest group was only .312".  

Further experimentation will be needed on the 22mm set-up.  Now that the crown issue has been addressed, I will be following up with group testing using both the HT and the factory muzzle weight.  This particular powerplant may very well prefer the added heft of the factory muzzle weight.  Previous testing revealed .25" groupings at 49 yards on this set-up using the factory muzzle weight.

I hope you found this HT Testing interesting and helpful.  

Up next will be an article that focuses on the two powerplants and some of the differences between them.


Steve

What follows is the same story told from two sides.
I have written my side of the story exactly as I recollect it, and respect that the other side recollected something slightly different.
That's life, we're all different, we share some things, we even may "commune" in some selected areas of the human existence, but we are never the same.
And that is good, that is well. RESPECT for the "otherness" of the other is what is needed in this world.
Luckily, we, airgunners, have a bit more of that respect than other "strains" of humans.
​Possibly it is the fact that the  REAL adversary is the environment. We do not look to overpower the wind with huge MV's and BC's greater than 1, we strive to KNOW our gun and pellet, and to "be one" with the conditions.
I find in that a very "Zen" attitude, worthy of any Kyūdō  archer.
Having said that, I am pleased to include here the text by Tim Higgins, a very special friend that understands the harsh realities of being "slightly" different than the rest of the world. With utmost respect, I yield the floor to "Higgy"

​" We've all heard the old proverb; patience is a virtue. Well, when you are a left-handed airgunner, it can be quite a challenge to remain virtuous . . .
 
         In 1980, I was 13 years old and had the great fortune of being introduced to the world of fine German air rifles. It was a Feinwerkbau 124, purchased new by my brother in-law which sunk her claws into me, and I would never think about pellet rifles in the same light again. A new appreciation was born, and I had an immediate love for the finery of spring guns. Like most young and impetuous boys, I had more energy than money and I certainly lacked the means necessary to fund my own quality air rifle.
I would have to be content shooting the 124 when I was lucky enough to have the chance and trust me when I say it was never enough.
I remember marveling at the deluxe stock with raised Monte Carlo cheek piece and wondering about how much better I could shoot if I could just take advantage of that technology. If only that wooden pillow thing were on the other side of the stock, surely, I could outshoot my brother in-law, and everyone else for that matter.
 
It's funny what you think in your adolescence, and funny how you remember it. It did make an impression on me. The rifle was clearly made for someone that shoots differently than I did, and though I tried shooting right-handed it felt like wearing a left footed shoe on my right hand and I hated it. Though the presence and placement of the cheek piece on the 124 was probably insignificant to my accuracy, it would be a recurring theme in my equipment choices for the next 40 years.  

​       Here is the funny thing about air rifles and air rifle enthusiasts, we are a strange breed. Myself, and countless others enjoy every facet of airgunning. The hunt for rifles and parts, the rebuilding, the tweaking and tuning, and more tweaking, shooting for tight groups, the chronograph plotting, and on and on.
So it should come as no surprise to anyone that my plan was to refinish the stock, pay whatever I have to for a diopter set, front sight insert, and send the rifle to Airgunwerks for a total rebuild!
​After all, I’m in this deep so why not keep digging...
In all fairness, after handling  the HV for a while, there was no second guessing  that the rifle deserved every bit of time and effort about to go into this restoration,  all the while knowing I was working on a rifle that would never fit me well. Like the legendary Pygmalion, the project became much more about THE rifle rather than MY rifle and I would be happy to own such a work of art regardless of its dexterous affiliation. 
 
       As always, when you throw enough time and money at a job it gets completed. The 75 was rebuilt, refinished, missing parts were replaced, and it shot like a dream, especially for a right handed shooter... Yes, you guessed it, I now wanted a left-handed 75 more than ever. I had tasted the fruit and it was sweet! Just imagine if I had the advantages of that wooden pillow thing but on the other side of the stock, I could surely out-shoot my brother in-law and everybody else for that matter! 

Some things never change... 

​Now to the more serious component of my 75 story:
​
   Upon completion of this restoration, I found myself staring at my 75   more than shooting it. So much so that I made a remark in a forum post about just how purposely handed the Diana 75 really is. With its beautifully sculpted trigger hand grip with palm swell, and a butt pad that provides what I would call cast on or cast off depending on if it is a left or right-handed rifle. I mentioned that I may even sell my 75 to pursue, yet again, a left-hand version. Enter our humble host, Hector.
Mr. Medina sent me a message about an excellent left-handed rifle his lefty shooting wife used and the prospects of a possible trade for my 75HV. I was quite familiar with the rifle and though it is an outstanding Steyr ten-meter beauty, it would be a bit redundant in my collection and Man!... I really just wanted a left-handed 75.

Hector’s world travels and Diana/Germany connections were not lost on me and gave me an idea. I inquired about the possibility of Hector acquiring a left-handed stock from Germany and I would buy it or trade it for my right-handed stock. Well, Hector is a man of action more so than of words and the next message I receive from him is that he is pursuing the purchase of a true left-handed 75 in good working order from a seller in Germany! The following message I receive is that Hector, with the help of his friends in Germany, had purchased and picked up the rifle, verified its proper function, and shipped it to CCA! Hector and I made a mutual and gentlemanly agreement and both rifles found new homes. Hector went well out of his way to acquire a model 75 in full left-hand action and stock and he now owns my right-handed model 75 HV. I could not be more pleased with the outcome and now I find myself not only staring at this beautiful work of art but shooting it too. 
Pygmalion now had a Galatea!
 
       It is true that patience is a virtue, but it takes many good and moral qualities to be virtuous. Compassion, generosity, integrity, fairness, and prudence are all examples of virtues. I experienced all these qualities in just one transaction with Hector and to say that I am grateful to him is an understatement. Hector achieved in four weeks what I had been trying to do for four years.
       The airgun community is full of great people, great equipment, and great times. I suggest you avail yourself of all three. And for goodness sake, talk to people in the airgun community. Years of searching did not find my favorite rifle, but a few friendly conversations did. 
 
 With appreciation, and kind regards,
 
 Tim Higgins"

And now my notes:

Being married to a left-handed shooter, and playing golf left-handed myself, I can understand the "Angst" of being left handed and having to shoot a right handed gun.

Now, most left-handed persons have become so inured to the fact that the world is right-handed that they don't grieve too much.

When looking for the first rifle to give to my, then, girlfriend. I came across the HW95, that for some strange reason had the safety button on the "correct" (to consciously avoid the term "right") side for left-handed shooters.
The stock was reasonably ambidextrous and her "engagement rifle" (as she calls it) was a success. Furthermore, I created a monster because she was the one that would insist we go out pesting for grackles over the weekends, LOL!
When we started shooting FT competitively, and after she changed over to a DIANA 54, she beat the heck out of me more than a few times.

Then she decided to be a mother and shooting was over for a time. Hopefully, it is one of those things we can do later as a family, when the kids get to be at least 7 and 6. BTW, Sofia, my little one shows some signs of being left-handed prone already. No worries, Daddy understands.

All this to tell you how "attuned" I am to the plight of the left-handed shooter.

I know that not all manufacturers are so attuned. Many offer rifles ONLY for the right-handed shooter, and some stocks are so aggresively right-handed as to make them unusable for the lefties (just look at a Weatherby stock of the 70's with "Roll-over MonteCarlo" and you will see what I mean.

One NOTABLE exception was the 60's DIANA branded Match rifles from Mayer & Grammelspacher.

The “Modell 60” (first rifle with the double piston "Giss" action) was truly ambidextrous in the sense that a break barrel with a smooth Classic Style stock can be shot from both sides easily. And a great left handed gun could be had simply exchanging stocks..
The 60 has no barrel latch, so it is easier to shoot fluidly, but I prefer to have the barrel latch.

Then came the 65, the last of the "sporter stocks" in Match rifles. This one was sort of a "metisse" in the sense that though Right-Handed guns HAD a right-handed "Wundhammer" swell, Left-Handed stocks could be had (as above), and if that was an expense the shooter didn’t want to go to, the stock was still VERY left handed friendly.
It is still my favourite "Match gun", even over my Steyrs.

Then came the 66, and that was an all-out Match gun with angular "Teutonic" stock, it was still a break barrel and so, the obtainability of left-handed stocks cured the problem for the lefties.
The wide distribution and acceptance of the Olympic Match airgun brought forth the 75. A sidelever with the "Giss" action, like its predecessors, but this time, the lever itself defined the "handedness" of the rifle.

Anything Olympic means substantial money, and so DIANA ventured not only into the airgun 10 M Match, but also into the KK (50 meters) RF match guns. They are still sought out as being among the finest "vintage" RF Match guns obtainable.

But, back to airguns. The 75 NEEDED a "mirror image" rifle to allow proper, ergonomic, operation by left handers.
Let's face it: Olympic Match is not about marksmanship; it is about ergonomics. How the gun fits the shooter is more important than how the gun shoots (within limits, of course).
Yes, it has to shoot within a specific range of precision and accuracy (2 mm’s deviation in any direction is max allowable deviation), but modern ammunition and modern barrels actually make it pretty easy to achieve "Match" quality performance from many platforms; in a vise.
Put a badly designed rifle in a top shooter's hands and it will not be "Golden" material.
Put an excellently designed rifle, even if it just barely meets the "Olympic Match" criteria, and you have a rifle that will win gold medal after gold medal.

And so, the 75 "LinksSystem" was born. An EXACT mirror image of the right-handed gun. Yes, most parts interchange and are common to both versions, but there is a fair amount of parts that are EXCLUSIVE to either handed version.
If you consider how expensive this is for everyone, including the manufacturer, you realize that it is an EXCEPTION to the rule.

Fairly recently, Steyr was the first to recognize that and start producing actions that can be converted to right or left-handed versions of themselves. In the past, actions have been either right or left-handed.

When we (DIANA) started cooperating with Snow Peak Airguns, one of the first things we noticed was that they already had the left-handed version of the gun in the pistol. Not exactly, and they are not truly interchangeable, but the basics were there.
A few Emails later and the first left-handed rifle actions in MANY years came into being, that followed by the truly ambidextrous synthetic stock created the first true opportunity for left-handed shooters to shoot in comfort form their "strong side".

From experience I know the disappointment that comes to the left-handed shooter when he/she shoulders for the first time a "wrong-handed" stock/action.

It is the moment of hope and the moment of disillusion, the moment of light and the moment of darkness, the moment of reason and the moment of terror.

So, when a well esteemed member of the "German Gate" forum decided to mention that he was willing to let go his right handed DIANA 75 RH version because he could not shoot it as well as he thought he should  be able, I decided to try to alleviate his situation.

We exchanged a few EMails; the first option offered was to exchange his DIANA 75 HV for a left-handed Steyr CO2 Match rifle in pristine condition, but he is a spring-piston shooter through and through and he denied. Second attempt was to try to obtain a truly left-handed version of the DIANA 75 for him, we could then exchange guns and, if both of us were happy, we would reach an agreement.

As luck goes ('Synchronicity' a well know writer would call it), a left-handed version popped up for sale in Germany from a very special source.
​North Germany, even, and it was for sale ONLY on a personal pick-up basis.
In normal conditions, that would have been an impossible target to shoot at BUT, "I knew a guy", LOL!

And so, started the long process of setting up an international operation that had to coordinate four people, three companies and one rifle.

On an established line of credit DIANA airguns itself took interest in the operation and set a young aide to conduct it. An offer was made on the auction site with a generous limit set.
We won the auction and the young aide picked up the gun in person. I am told that the owner was marveled at the fact that the original manufacturer had taken an interest in “his” gun and lamented that he had not contacted the company first, as the gun had some historical significance (more on that later).

In any event, the owner was happy that the gun was sufficiently appreciated to be destined to be exported to a foreign country where an article would be written about it. And he congratulated himself on taking care of a gun that, for all intent and purposes, had been declared "surplus".

So, here it is, in your honor and with our thanks, Herr Kaufmann (not the real name but in German Kaufmann means "trader/merchant"). Your gun has found a new home in "Amerika" where it will be well taken care of, shot often, loved much, and displayed as one of the pinnacles of spring-piston airgun manufacturing.

Vielen Dank!

​The gun then stayed for a while in Germany, because one of the conditions was that the gun would be tested by the in-house technicians and declared "fit for purpose". Of course, guns have no "word of honor", LOL! and a perfectly working gun can fail in a few days, or weeks, or months.  But at least we had a "looksie" by someone that knows what they are doing before starting the proverbial 10,000 miles trip.

After all the appropriate paperwork was filled and permissions obtained for the export/transport, the gun started its trip.
And then it arrived in the US.

As I notified Mr. Higgins, I could feel that he was indeed pleased with the opportunity.

Because he had to travel, he sent his RH versions straight-away, and so, I took advantage of having BOTH guns and proceeded to take a suite of pictures, which have been interspersed throughout this article.

As you can see, it is TRULY a mirror image.

And now to close the story, let's go back to those statements about "declared Surplus" and "historical significance".

If you note in the pictures, though the stock on the LH version is not the "commercial" stock, being somewhat austere, it is fully functional and has all the adjustments needed, just not as pretty.
And then there are these "BKA" markings and number, ¿What do they mean?

Well, here is the kicker:

The Bundeskriminalamt (BKA)  is the German Federal Criminal Police, something closely related in function and authority to our own FBI.

¿How would you feel if you found an airgun with "FBI" markings?

;-)

I am sure that there is no better home in this world for this specific gun than Mr. Higgins' home. His work in the RH 75 HV stock is absolutely flawless and I am very happy to have played a small part in the history of this gun.

Like Old Soldiers, glorious guns never die ... and with the participation of good airgunners, hopefully they will never fade away either.

There will be more chapters in this gun's story in the future thanks to the loving passion of a few good men, who established a chain of brotherhood across languages, continents, oceans, and years.
​And THAT is part of the magic of airguns.

Keep well and shoot straight!






HM

A Guest Blog by Stever Herr

PROLOGUE by Hector Medina (Editor)

As humanity moves along in its "progress", it is more and more clear that the only thing that is constant in the UNIVERSE, is: change.

The modern world has brought a number of inconveniences (like worldwide running Flu's), a number of disasters (like Global Warming), and a lot of veritable Tragedies (The continuous State of War since the beginning of the 19th Century).
BUT, it has also brought serious marvels; some of them, undoubtedly, double edged swords that can cut either way.
Among those marvels is the Internet and the level of communication that we can have now with people we have not ever met face to face. And, yet, the commonality of passions, the willingness to suspend (or lower) the "offense" level, and the usage of a "lingua franca" (English), allows us to work; share knowledge, ideas and experiences; and grow together with people that are hundreds of miles away, or thousands, it really doesn't matter.

And that enriches our life. Yes we can cuss the internet for the amount of garbage that we receive on the EMail everyday, but we also have to be grateful for the genuine and wonderful communication opportunities it affords us.

This FOUR PART SAGA is the result of one of those opportunities. A veritable "meeting of minds" that resulted in some fantastic experimentation and some solid science being made.

And so, without further ado, I yield the floor to the Steve Herr, the Gentleman from Pennsylvania, noting that it was a privilege and a pleasure to work with such a fine mind in these experiments.

​A 56TH Gone Awry
About 7 months ago I purchased a Diana 56TH in .177.  This was my first Diana with the sliding action design and I was anxious to give it a try.  After much reading and correspondence with Hector Medina, I tore into the rifle, going over everything from top to bottom.  The sled mechanism was polished up, T06 trigger disassembled, polished, relubed and set to a mere 8.2 oz pull.  The powerplant was replaced with an AGT 22mm skirtless design from Tony Leach, and the sled tension was tuned for best groups on target.
While I was very pleased with the results, I was seeing some fliers that concerned me.  It was shooting extremely well, don't get me wrong....but the fliers weren't going away.

After much work to try and resolve this issue, I turned my attention to the factory crown.  The factory crown had been machined at a slight angle, see attached picture.  When looking at the crown you could see that it was deeper and wider in the area of 1:00 O'Çlock to about 7:00 O'Çlock. You could also see that the grooves were blocked off along the edge in the area hi-lighted in yellow with only 5 of the 8 grooves being visible. 

​I finally decided to hand lap to see if I could improve on the crown, and help with the issue of occasional fliers. Using a brass hand lapping tool from Brownells, I went to work.  After the hand lapping, I was now able to see all 8 lands.  However, the crown was still angled.  If there is a lesson to be learned here, hand lapping will not correct a crown that is not square to the bore.  In fact, it may actually make the angle worse.
Here is the crown after Hand Lapping.

​After hand lapping I returned to the target to see if there were any improvements.  At 32 yards it was quite apparent that not only was the problem unresolved, but it had actually gotten worse with groups beginning to scatter.  As the title of this article indicates, this rifle was going HAYWIRE!!

After many hours of experimentation to try and resolve, I reached out to Hector to see if he knew of anyone who could re-crown a barrel square to the bore.  I was pleasantly surprised to find out that this was a service that he performs in most of his builds, and that he would be willing to look into my barrel in detail. 

We also discussed the heavy factory muzzle weight, and the tendency they may have in contributing to fliers.  He suggested some options for replacing the factory muzzle weight.  The options offered were a Harmonic Reducer or a more simple design called a Harmonic Tuner.  I said that I was open to his suggestions and would go with whatever he recommended.

A short time later my rifle was completely stripped down and the bare barreled action along with the barrel shroud was on it's way to Hector.

After evaluating the rifle, Hector began the process of re-crowning.  Here are a few pictures showing the step-by-step process.    Hector continued to machine the surface until the entire internal edge was the same depth and square with the bore.    If you look closely you can see how the crown was squared up nicely.  ​

On the final step, Hector added a taper around the outer edge, the end result being a nice target crown.

Hector's next step was to verify that the barrel would shoot.  In order to do this, Hector utilized one of his own powerplants, tuned to the desired level that I would be shooting the rifle (11.4 fpe), and using the same pellets that this rifle seems to prefer...JSB Exact 8.44 (4.53).  He also installed one of his stocks and a scope for the testing.
At 35 yards in a seated position (not benched), Hector confirmed that the rifle would offer up nice uniform groups rather than the scattered groups I had been seeing previously.

It was a HUGE relief to hear that Hector was able to save the barrel on my 56, and seeing the more uniform groups returning on target was extremely encouraging!
A job well done!!!
After the recrowning, Hector moved to the next part of the project, that being a suitable replacement for the heavy factory muzzle weight.  I will cover that in another write-up.

​
Steve