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The "HPM" or DIANA's High Performance Muzzleweight

4/25/2020

13 Comments

 
I have received some questions about this system (yes it is a SYSTEM), as well as a specific request from one of my favourite persons in the airguns' cyberworld, and the questions tell me that without the IWA 2020 happening, a LOT of what WE (DIANA) had hoped to relay to the users and accomplish on the shooter's information side simply DIDN'T  happen.

Questions also tell me that people are not really up to date about where the research and development of spring guns is going. In a way, that is understandable, manufacturers are not doing the best of jobs in telling people how more advanced today's spring guns can be in relation to those airguns that the Cardews' analyzed in their legendary works.

So, let's look at a little bit of history and how it percolated into the production line of one of the foremost examples of applied technology in the spring-piston airgun world, then we'll look into more recent experiments, and how, finally, the product became a system to be included into the new edition of the Air King (the AirKing Pro). Along the way, we'll discuss how sometimes even manufacturers fail to recognize the DIFFERENCES between an airgun and a firearm.

So, let's get started:

A bit of history

Ever since my powder burning days (1966 to 2000), I have been a firm believer in tuning the gun to the projectile, and choosing the best projectile to the task at hand. If you are familiar with the "Accuracy Node" concept, you know that all rifles have a MV where the bullet exists at the point where the barrel's muzzle's excursion is at its extreme. Meaning that it is going in one direction, stops, and then starts moving back. Like a pendulum, but in a much more violent manner. So, following that methodology, the MV of airguns can be changed in small increments through the use of spacers in the spring, so that the pellet's exit coincides with the end of the oscillation where the transversal velocity of the muzzle is as low as possible because it's either stopping, at rest, or just starting to accelerate back.

Therefore, when I came across a commercial unit that offered to do that for the DIANA's  I jumped into it. Over time, I found the unit somewhat fragile and capricious (getting out of adjustment at the worst possible time), till at some point, I had it glued (this commercial Harmonics Tuning product was discontinued about 15 years ago), then in 2015, as a result of its dismal failure in a WFTC Match, I decided to design something that would work in my favourite platform, the DIANA 54 AirKing.

Some time passed and I then came onto the realization of a basic characteristic of the DIANA 48->56 family: The barrel is in reality a 15.2 mm's barrel that has been encased in a shim and then that shim goes INTO an 18 mm's  sleeve, that is what we see. That is the nicely blued part that we take for a barrel, but it is not.

In the past, SOME shooters used to fill the cavity between the shim, sleeve and barrel with resin, or other compound, and claimed to have improved the accuracy, but my problem with that approach was that it was a FIXED solution. "Tuning" of your system would STILL need to play with the MV and finding the "right" pellet.

I wanted a simpler device, something that would allow you to re-tune the gun should you change pellet batches, or wanted to change brand, power level, or any other thing. Something that would allow you to set a velocity (according to some rules, or other criterion set by YOU), and then tune the gun to THAT. In other words, command the gun and not be commanded by it.

I looked at all the existing Harmonic tuning systems (firearms, archery, and airguns) and all but one depended on a weight that was knurled and screwed or unscrewed along some position in the barrel, or a rod. The one that didn't, depended on moving the support position of the barrel in the stock (forend pressure point bedding) therefore lengthening or shortening the free-floated length of the barrel, problem was that most spring-piston airgun barrels are free-floated by design.

So, I decided to combine both concepts and came up with a system that is comprised of a specifically dimensioned weight that can move back and forth along its position on the barrel with set spacers.
I worked through a few prototypes and when I had settled on something I published my results here in this blog entry.
Now, do note that this happened in 2016, that's 4 years ago!

Since then, most of CCA builds have benefited from this "gadget", and/or from the knowledge and techniques that this research brought. Further research has been done and now we know not only how to control, but how to REDUCE the harmonics at barrels' muzzles (though that is another story ;-) )

Almost three years ago, I started working closely with DIANA, and since there were talks to bring this technology (and others) to the public/shooters of DIANA airguns, I did not pursue further the commercialization of the product.

So, when the time came to write the spec for a "new" 54, it was normal for me to include this device into the spec. In complete agreement with DIANA, we decided to name it the HPM (for High Performance Muzzleweight).

The first appearance of the device to the public under the DIANA brand was at 2020 SHOT Show, there is a whole thread about it here where you will find links to videos, reviews and other comments; as well as a lot of questions and answers.

And that brings us up to the present

First proposal and a "failure"

It was towards the end of 2019 that I was told that about 300 "54 barreled actions" were available and that we could use those to launch a re-vamped 54.
The problem was that there was NO BUDGET available for improvements. Meaning that whatever we wanted to put in, had to come from reductions and savings in the SAME model, that is a tough value-engineering problem: Improve a product AND make it cost the same or less. Not easy without a technology leap. Still the challenge was taken up by the team and we discussed a number of things that could be improved. Sadly, ALMOST ALL implied some cost increase. The exception was the Harmonics Tuner. A muzzle piece needs to be there, and the plastic one in current production, though not expensive, is not cheap either. It's a complicated mould. Also, the change COULD imply that the "Pro" model would be a scope-only rifle, so the sights could also be eliminated. Lastly, there was an extra operation on the barrel to create the "key" where the front fight ramp/muzzle piece needs to index to always keep the front sight straight up. Between all these "savings" the Harmonics  Tuner seemed to be a good candidate.
It also promised to be the most value for money that would still be useful to ALL shooters (and here I want to remind you that DIANA operates in more than 90 countries with 7 different power levels and some caliber/rifling/OAL legal complications).

And, finally, adapting it to the EMS system would be a breeze, so, after much thought, the concept of the Harmonics Tuner came to the forefront. The part is simple to make and easy to use, it does NOT come out of adjustment, and use tends to affix it more and more firmly into its place.

Simultaneous to that I had started some serious work with a friend with a scientific penchant that tested the usefulness of the Harmonics Tuner in two completely different power plants: A short stroked D56 and the "skinny piston" (22 mm's compression chamber bore) version of the same gun. As different as apples and oranges.
You can read the results of those experiments here:

https://www.ctcustomairguns.com/hectors-airgun-blog/the-saga-of-a-56-th 
https://www.ctcustomairguns.com/hectors-airgun-blog/the-saga-of-a-56-th4603110 
https://www.ctcustomairguns.com/hectors-airgun-blog/the-saga-of-a-56-th8042880 
https://www.ctcustomairguns.com/hectors-airgun-blog/the-saga-of-a-56-th2541108 

As you can see from the whole SAGA, the Harmonics Tuner proved its usefulness in two completely dissimilar engines. It would be like testing a turbo-charger in a Mack Diesel Tractor Trailer and a Subaru BRZ and still finding improvements in both results.
And the HT was deemed an "easy to use" device, needing the release of the screws, the addition or subtraction of an ORing and the reassembly of the gun, an operation that took less then 3 minutes per test.

So, it was DOUBLY annoying when DIANA's head gunsmith told me that they had not found any change in group size when tested in the factory, regardless of the number of spacers added.  WHAT?
Luckily, the Technical CEO told me that they would still go ahead and planned the use of the device, but that I had to come up with a new design, test and a procedure to demonstrate the usefulness.

After taking a day (or two) to calm down and analyze the whole thing, I decided to question the test procedure followed by the factory. It was then that I was told that the gun had been put on a vise that held the sled system fixed, but at an angle, that changes had been made from the original spec (aluminum instead of steel), and that only two screws, instead of the 6 that were originally specced had been used, granted that perhaps my drawing had not been completely clear, but still the device built by the "Construction" section of the company was not what I was talking about, these substantial changes warranted a re-design and re-test, under conditions that would be found in real life shooting.

And here is where there is a lesson: If you need to test something that is going to be used under field conditions, then test it under the same field conditions.

A new material was sourced as Aluminum DOM bar, and new prototypes were made, but this time complying with the needed weight (one of the most lengthy sets of experiments I ever conducted way back in 2015).
I then prepared a completely new test using one of the guns that were on the pipeline, and these were the results:
Picture
As you can see, adding or deleting ORings yielded observable and measureable results. Dispersions went from horizontal to vertical and then back, and too many ORings (same as too large a weight) produced horrible results.

With these results in hand, I went back (electronically) to DIANA, and it was agreed that the AirKing Pro would come equipped with the device.

The device itself is VERY simple and easy to make. From the outside it looks just like an average Muzzle Weight, but the trick is on the inside, where ORings can be added or removed to determine the position of the weight along the muzzle. In the same way that using a longer or shorter bar changes the "tone" of a grandfather clock carrillon, the harmonics (vibrations) at the muzzle also change and this is what determines the POSITION of the muzzle and WHERE IT IS AIMING AT, when the pellet exits the muzzle.
Picture
Picture
As ORings are added, the muzzle that was flush with the end of the HPM, becomes more and more "recessed" into the cavity.
Using one of Steve's excellent pictures, although that is a steel version of the HPM for the model 56, not the 54, you can see the make up of the whole system
Picture
The other difference you will find is that while 3 screws are enough for 12 ft-lbs, for 24 ft-lbs you need 6.
But the principle is the same: You add or delete ORings to bring down the group size with the pellet you want to use (within reason).
As it was demonstrated and re-tested, in a normal 54, the results were verifiable and repeatable:
Picture

The Future

Picture
Between 4 and 6 months after "re-start" of the world's economy once CV-19 has been overcome, we should be able to see this in retailers and internet sellers.
There will be other options in stock colors and, of course, a beech version.
The process to "tune" the rifle's harmonics will be the same: 
1.-Start from 0 ORings
2.-Shoot three shots into a "waste" bullseye
3.-Shoot a 5 shot group at least 15 meters away (19 is preferrable).
4.- Add one ORing
5.- Repeat from 2
6.- Repeat from 4
When you reach 10 ORings, STOP, you should see a "periodicity" each 4->6 Orings (depending on power level), settle on the two settings that are most promising and re-test till you are happy that you are at the best possible point.

I would advise to "Run in" the rifle BEFORE the tuning (if in doubt about what is the BEST way to do this, read this), as the wearing in of the parts amongst themselves is an essential part of what airguns need to be able to deliver top accuracy, but if you want to "train" yourself in the procedure by all means do it several times. Just understand that, in the end, you cannot put the carriage before the horses.

Hope this answers as many questions as is normal before seeing/handling the actual thing.

Always open to questions or comments.

Keep well  and shoot straight!





​HM
13 Comments
Javier Muñoz
4/27/2020 00:28:21

Hola, espero que entiendas español. Quiero usar una pistola PCPRebel PP800 con el cañón de 19" del Diana Stormrider.
Todo en .22". ¿Hay algún detalle que se deba considerar, tiene el cañón Crosman de 22" compatibilidad para montarlo en esa pistola?.

http://www.canadashootingsupply.ca/diana-stormrider-barrel-22-caliber.html

Saludos

Reply
Hector Medina
5/1/2020 07:53:50

Javier;

Los cañones del Stormrider son compatibles con los cañones de la Bandit. NO sé si SPA haga alguna differencia en los recibidores de las diferentes marcas para las que produce.
Crosman es otro boleto y tendrías que tener un buen taller para lograr la adaptación.

Sorry, pero no te puedo contestar con más detalle.

También te pido, de la manera más atenta que en el futuro pongas los comentarios donde sería lógico encontrarlos. Por ejemplo este podrías haberlo puesto en una de las varias entradas en las que tratamos el Stormrider.

Un saludo y te deseo mucha suerte!




HM

Reply
john eroh
5/1/2020 02:57:50

Do you think my 430L would benefit from one of these? It's damn accurate as it sits. It's good to see one of your projects come to fruition Hector.

I hope for you and your families continued health.

Reply
Hector Medina
5/1/2020 08:02:04

Hello John!

Didn't know you had bought a 430L! Nice, thank you!

The PRNCIPLE for sure would work, but using an OEM piece would imply substantial modifications to both, the gun and the muzzle piece.

There is ONE way where the principle could be applied to the 430L with the existing muzzle piece (I need to weigh it and do some maths), but it should be possible.

If you are interested, drop me a line through the contact page, or send me an EMail.

Keep well and shoot straight!




HM

Reply
dan house
5/1/2020 11:56:34

"After taking a day (or two) to calm down"..... Wow that must have been some conversation... Ive never known you to be anything but chipper, cheerful and smiling!

Will these be available as a seperate purchase?

Reply
Hector Medina
5/1/2020 12:03:11

Hello Dan!

Yes, that is the plan.
Perhaps there will be a delay between the availability of the AirKing Pro and the availability of the HPM as an aftermarket accessory / part, but the idea is that yes, they will be available for the wholesalers to order them.

My suggestion to all readers would be to start sending Emails to the wholesalers (UMAREX, PA, and AoA) and let them know that you are interested in one of these.

Thanks for reading!





HM



Reply
Bill Bratt
5/8/2020 13:18:19

Hello Hector - I have just recently discovered your blog and am “blown away” by the info/knowledge contained therein.

I too would be interested in having one of these on my 430L providing it wasn’t too complicated in replacing the existing muzzle weight/latch.

I would also be interested in learning if this HPM would work on a Beeman R9.

I very much appreciate your continued work/efforts in advancing the quality/accuracy of “springers” as I find their simplicity of use the big attraction, and I have absolutely no interest in PCP’s.

Thank you for sharing your knowledge leading to continued improvements in my favourite air guns.


Reply
Hector Medina link
5/9/2020 12:52:00

I've been doing some tests with the OEM muzzle piece of the 430, but the spaces in there are too big, so it seems that the best bet is to make a special part, do away with the spring loaded balls latch, and use a magnetic latch, make the piece of the proper weight (the OEM is more than twice the weight required), and then have the proper clearances in the design.
My estimation is that the whole piece would come at around $125 with the spacers.
I am also working on an "Easy cock" piston. but that would also require a different spring and guide.
Lots of projects too little time.
Once I have tested the whole thing, I will let everyone know.
Thanks for reading, keep well and shoot straight!



HM

Reply
Roberto Delgado
9/19/2020 00:18:07

Hello Hector.
I have read your publications and tests carried out with Diana 48/52/54, for 1 year as well as your participation in FT, I have some questions ab the out the new Air King pro
1) The new Air King Pro has 2 versions, Laminate and Beech, the laminate has the "muzzle", but the beech does not have it, or does it have it? (Plastic).
2) If the Haya model has the "muzzle", how can I remove / put O'rings?
3) If I want to do these tests, do I have to buy the laminated version?

Thanks for sharing your knowledge.

Hola Hector.
He leído tus publicaciones y pruebas realizadas con Diana 48/52/54, desde hace 1 año asi como tus participaciones en FT, tengo unas preguntas respecto al nuevo Air King pro
1) El nuevo Air King Pro tiene 2 versiones , Laminado y Haya, el laminado tiene el "muzzle", pero el de haya no lo tiene, o ¿si lo tiene ?(plástico).
2) Si el modelo de Haya tiene el "muzzle" , ¿Como puedo quitar/poner O´rings?
3) Si quiero hacer estas pruebas, ¿Tengo que comprar la versión laminada?

Gracias por compartir tus conocimientos.

Reply
Hector Medina
9/19/2020 09:17:39

Hola Roberto!/ Hello Roberto!

1) Yes there are two versions of the stock. The PICTURES show differences, truth is that the guns will/should come with the normal muzzle piece, and the HPM should come in a baggie. /
1.-Si, hay dos diferentes versiones de la culata. Las fotos del catálogo muestran dos "modos" diferentes, pero las carabinas vendrán/deberían venir con las piezas de boca norrmales, y los HPM en una bolsita separada.
2) The HPM have two screws, you just loosen them a little, take off the HPM, add/remove ORings and that lengthens or shortens the position of the HPM, it is this POSITION of the weight what will tune the barrel harmonics to the energy and pellet you are using. /
2) El HPM tiene dos tornillos. Los aflojas un poco y el HPM se desliza, lo retiras de la carabina y entonces puedes agregar ó añadir ORings. Agregar ORings alarga la posición del HPM, retirara ORings acorta la posición. Es esta POSICIÓN lo que sintoniza las armónicas del cañón al diábolo y nivel de energía que estés usando.
3) No, the beech version should also include the HPM in the box. /
3) No, la versión en Haya también debe de incluir el HPM en la caja.

IMPORTANT NOTE: The ORIngs you will need are M 1.5X13 70 ShA and you can use up to 10 Orings,

NOTA IMPORTANTE: Los ORings que necesitarás son los M 1.5X13 70 ShA y puedes usar hasta 10 ORings.

Thanks for reading us / Gracias por leernos!




HM

Reply
Roberto Delgado
9/21/2020 14:52:23

Hola Hector.
Basado en toda la información de tus blogs y en las pruebas que has realizado con tu Diana, el día de hoy acabo de ordenar mi Diana 54 Air King Pro Haya en cal. 4.5 , claro, debo de esperar cerca de dos meses para que llegue el rifle a Mexico.

Reply
Patrick
1/5/2021 19:32:11

Hi there,
Where can I buy the HPM for my D48 ?
Thank you

Reply
Hector Medina
1/5/2021 19:48:13

Drop me a line through my "Contact Page".

You have two options:
a) DIANA made HPM, two screws, same geometry, a bit loose fitting but they work, anodized matte black , ready to ship.- $50 + Sh & Ins,
b) CCA version, 6 screws, more tightly fitted, three to four weeks, natural finish.- $80 + Sh & Ins.

Reply



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    Hector Medina

    2012 US National WFTF Spring Piston Champion
    2012 WFTF Spring Piston Grand Prix Winner
    2013 World's WFTF Spring Piston 7th place
    2014 Texas State WFTF Piston Champion
    2014 World's WFTF Spring Piston 5th place.
    2015 Maine State Champion WFTF Piston
    2015 Massachusetts State Champion WFTF Piston
    2015 New York State Champion WFTF Piston
    2015 US National WFTF Piston 2nd Place
    2016 Canadian WFTF Piston Champion
    2016 Pyramyd Air Cup WFTF Piston 1st Place
    2017 US Nationals Open Piston 3rd Place
    2018 WFTC's Member of Team USA Champion Springers
    2018 WFTC's 4th place Veteran Springer
    2020 Puerto Rico GP Piston First Place
    2020 NC State Championships 1st Place Piston

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