Diana 56TH .177 - AGT 22mm Skirtless Conversion

[subscriber]

[It would be interesting to see both small diameter and slightly larger diameter syringes being compressed into a common sized syringe with a quick motion compression as in your video link.

Then I had better order some larger (or smaller) syringes.  I no longer work in inkjet, where syringes were an everyday consumable

I know for sure that when you whack a 20 ml syringe connected to a 10 ml syringe, the plunger on the latter flies out with alacrity; and produces a satisfyingly loud uncorking sound.  Much to the chagrin of my collages at the time 

This stands to reason, as even moving the larger plunger slowly will drive out the smaller one.  As I recall, the sensation of resistance to rapid compression against your hand is also noticeably higher with a larger area syringe.

Perhaps I need to drive the syringes with elastic surgical tubing to have a more controlled input, that also does not hurt my hand...

[subscriber]

I was waiting for someone to say; "this thermal air volume multiplication effect is the reason why springers are more efficient than PCPs.  With PCPs, the time constant is so long, all heat of compression is thrown away." 

In other words, if you shorten the time constant beyond that of the typical springer, more heat of compression ends up in the air driving the pellet.  The small area light piston of the 22 mm skirtless conversion seems to achieve exactly that.

[HectorMedina]

Peter;

Thing is, the difference between adiabatic and isothermal is not well understood.

And, on the other hand, the phenomena we're concerned here with are so fast, that we do not have any way of perceiving, with the normal senses, what is happening. So, we get stuck in our small world of perceived "smoothness of shot cycle" when in reality what is happening is far more complex and dynamic. Even a specialized accelerometer has difficulty reading some of the vibrations generated.

Now, We may not feel it, but the scopes do.
And claiming that the scopes are not good enough and are not "keeping up" with the "advances in technology" is, IMHO, non-sense.

Also suggesting that shooters limit themselves to perfectly centered scopes and use hold-offs instead of clicking is somewhat contrary to the general trend in the sport these kits claim to serve (FT).

Consider that most "advanced" shooters do the "box test" of a scope with 15 clicks either way. That is a total of 30 clicks.
By comparison, an FT shooter will use a full revolution (and a bit more in some cases), to deal with the trajectory changes between Apex (22-23 meters) and 9 meters (10 yards). In my particular setup, I would need to click 150 clicks to go from 9 meters to 23, where the Apex is, and then re-elevate 100 clicks to get to the 50 meters/55 yards target.
A 30 clicks "box test" is really NOT useful under these requirements.

I will not say anything further about this because there are people here much better suited and experienced than I am with these kits.
I quit testing these kits when the altitude problem became an absolutely insurmountable obstacle.

We have offered one of the most important scope manufacturers to do some real vibrations testing, but I am not sure they will want to go ahead because the market is so diminutively small and the needed sensors are so exorbitantly expensive.

:-(

Keep well and shoot straight!







HM

[fwbsport]

Peter;

Thing is, the difference between adiabatic and isothermal is not well understood.

And, on the other hand, the phenomena we're concerned here with are so fast, that we do not have any way of perceiving, with the normal senses, what is happening. So, we get stuck in our small world of perceived "smoothness of shot cycle" when in reality what is happening is far more complex and dynamic. Even a specialized accelerometer has difficulty reading some of the vibrations generated.

Now, We may not feel it, but the scopes do.
And claiming that the scopes are not good enough and are not "keeping up" with the "advances in technology" is, IMHO, non-sense.

Also suggesting that shooters limit themselves to perfectly centered scopes and use hold-offs instead of clicking is somewhat contrary to the general trend in the sport these kits claim to serve (FT).

Consider that most "advanced" shooters do the "box test" of a scope with 15 clicks either way. That is a total of 30 clicks.
By comparison, an FT shooter will use a full revolution (and a bit more in some cases), to deal with the trajectory changes between Apex (22-23 meters) and 9 meters (10 yards). In my particular setup, I would need to click 150 clicks to go from 9 meters to 23, where the Apex is, and then re-elevate 100 clicks to get to the 50 meters/55 yards target.
A 30 clicks "box test" is really NOT useful under these requirements.

I will not say anything further about this because there are people here much better suited and experienced than I am with these kits.
I quit testing these kits when the altitude problem became an absolutely insurmountable obstacle.

We have offered one of the most important scope manufacturers to do some real vibrations testing, but I am not sure they will want to go ahead because the market is so diminutively small and the needed sensors are so exorbitantly expensive.

:-(

Keep well and shoot straight!







HM

I know you're not saying anymore about this but I will, since trying out your Traditions scope in the Zero Recoil mount I rethought the scope and did something I thought I'd never do, mount the Beeman 4X 32mm scope--which reminded me of the scope on your rifle for crosswires and clarity--in the Diana Zero Recoil mount atop my HW80 .25.  I got to thinking scopes are ALWAYS presenting problems even if they are expensive and why not just put a cheap scope in a Zero Recoil Mount and see how well it sights in and holds its zero; as part of the experiment instead of trying to make an expensive scope selection!

Okay it's too early to tell I just mounted the Beeman 4X 32mm (fixed power by Beeman and real nice optics that beat most scopes!) but if it isn't working properly I'll just remove it and try another!

[TonyL]

All I am going to say regards altitude is this, you run 105mm stroke 22mm with a HW95 spring or UK spec Diana spring and you will see 900fps in .22 with 14,3gr pellets if you want it at seal level. You can down tune to 12fpe at sea level and uptune to 12 at 4000ft with just a little preload on or off, the stroke would allow this.  Everyone who attended the FT worlds in the UK re adjusted their guns for the competition when they arrived, some up tuned, some down tuned a little, all had to be under 12fpe for entry into the UK remember. Its just a case of run the stroke you need and adjust the preload up and down a little for the altitude if it was needed, im sat here thinking 105mm stroke might have such good tolerance you might not need to adjust at all.

I have a 20mm Diana 52 running 89mm stroke, yes 20mm, its making 770fps with 177 Exacts with a spring that would not even drive a full weight full size 52 piston to 4fpe, its from a junior rifle sold in Germany, the gun is amazing to shoot. If i lived at 4000ft i would run 105mm stroke, it would do just the same power with ease.

Altitude is a ZERO issues, only Hector thinks its an issue, i don't, i know the diameter of the piston is not the issue, only the stroke has to be changed to gain or lose power, for altitude tolerance just run more stroke...end of problem.

So a 20mm piston running 28CC of air is making 11fpe+ at 500ft over seal level with around 10mm preload, maybe less, on a spring from this https://www.frankonia.de/p/baikal/luftgewehr-ij-512/107964

I have witnessed 3/8th inch groups at 80yards with an MTC 10mag scope hard mounted using BKL 1 piece on a 20mm 56 at 11.2fpe shooting JSB express outdoors, total recoil on the sled was under 4mm, adding a scope cam to the scope resulted in a near clear picture being recorded of the full shot cycle, my fears of making guns just to fast are actually unfounded, small piston guns are not to fast at all, they are actually softer on scopes proven by the use of a scopecam and watching the pellet fly just like when used on pcps...
Ideally a frame holding the scope and stock and the action sliding back within the frame would counter all the issues sled guns can cause, there is an aftermarket solution already for the TX etc, the tech allows large scopes to be used with ease, the ONLY issues is getting that action to slide back dead true each and every time.

I hate battling on forums about issues that are none issues...

[subscriber]

total recoil on the sled was under 4mm

Thanks Tony,

How much does the sled weight, and is the rifle solidly coupled to the sled?  If the sled is heavy and solidly coupled to the rifle, the sled will reduce the total amplitude traveled; and damp out high frequency vibrations.

Would it be possible to suspend the rifle horizontally from two long thin nylon cords, with accelerators mounted to the rifle?

Anyway, there is no arguing with real results.  That said, goals may differ.  As long as the stroke length adjustment requirement is understood, potential customers can decide for themselves if they accept that as too much of a burden, or not. 

It almost sounds like an opportunity for an externally adjustable spring preload, that would not required removing the rifle from the stock.  Removing and replacing the action from the stock tends to upset stability; or at least, undermine confidence in stability.   Those that live in the UK have more opportunity to re-establish confidence and tweak their rifles before a match than do international visitors. 

Perhaps those in the USA are spoilt, but the old adage of not fixing anything that isn't broken is a good one.  Hence the reluctance to make fundamental adjustments to a system that is working well...

[Nitrocrushr]

The sled Tony was referring to is the rifle action moving on the internal sled within the stock.  My 22mm x 96mm stroke 56TH has less than 5mm movement on the action within the stock.


Steve

[subscriber]

The sled Tony was referring to is the rifle action moving on the internal sled within the stock.  My 22mm x 96mm stroke 56TH has less than 5mm movement on the action within the stock.

Thanks Steve.  That makes perfect sense, and is more meaningful to me than an additional sled, like you used.  Not knocking your instrumentation.  Some objective measure is better than just one man's "feel".

[Mossonarock]

that's neat that someone posted something about fire pistons.
I have a couple myself; one that I made.
They really demonstrate how hot the air in a springer's compression chamber can get in that wee moment of compression.

[Nitrocrushr]

I wanted to update everyone on my original 56TH AGT 22mm project above.  I was getting random fliers with this rifle and spent a considerable amount of time trying to resolve the issue.  I even purchased an accurized ZR mount from Hector Medina, thinking it was an issue with the scope being set in a solid mount.  Still no help.   In the end, the only thing I could determine that was causing the larger groups with fliers was the factory crown, which had been machined at a slight angle to the bore.  I tried to touch this up with a hand lapping tool, but groups were even worse after this.  Once a crown has been started at an angle, you really need the right tools in order to correct the angle and get it square to the bore.  Any attempt at hand lapping will more than likely follow the existing angle, and might even make it worse.

Here is a picture of the factory crown.  You can see that it is narrow and more shallow in the area of 10:00, and broader and deeper around 4:00.



After touching this crown up, although smoother...you can see that this angle remained unchanged.



In order to test this theory I decided to move the 22mm kit over to my brand new 56TH.  During this testing I tested both the AGT 22mm kit and the factory OEM power plant with a Maccari GSX FAC spring in each rifle.  All testing was done at 32 yards with my SWFA SS 10x42 scope mounted in Hector's Accurized ZR mount.  Sled settings and stock torque were set identical on each rifle.  Both triggers had been stripped, polished and set to about 8.2 oz.

Both tests failed in the old 56TH, with poor grouping.  The groups got even worse with the increased velocities using the OEM power plant.  Several pellets were tested with no success.

Moving on to the new 56TH (made in the Ense facility), both 22mm and OEM passed with flying colors!  Nice tight grouping.

I then ran a partial box test with the 22mm AGT kit of 30-clicks to verify that the scope would track.  It tracked very well, to the right 30-clicks and back to same hole - see below;



Today I expanded upon this and ran a test vertically at 32 yards.  This time I tested the scope over a 100-click range.  Keep in mind that the SWFA SS 10x42 has 1/4 moa turrets, so this was a substantial amount of movement.  The rifle, mount and scope passed with flying colors, returning back to the exact same hole

In the photo below you can see I have the testing listed in order numerically;

1) Mechanical zero - 5 shots
2) Up 50 clicks - 5 shots (a cross breeze was picking up on this one so I got a little horizontal stringing.  I put up a wind flag after this and timed remaining shots as best I could)
3) Down 100 clicks (which put me 50 clicks below mechanical center) - 5 shots
4) Up 50 clicks (back to mechanical center).  Shot landed in the exact same hole

I was very pleased with the results.



Sometimes issues can creep up that have you at a loss for answers.  Persistence paid off in this case.

For anyone wondering how well Hector's Accurized ZR mounts hold up and repeat from shot to shot, as you can see they have very solid repeatable POI on target

My old Rastaat made 56TH will be shipped off to Hector this week to have the crown squared up to the bore.  I am also going to have him make one of his Harmonic Reducers for it, finished in a Matte Black Cerakote.

Here are some pictures of the new 56TH as it came out of the box....and then again after it was all set up with an SWFA SS 10x42, Hector's Accurized ZR mount and the AGT 22mm kit set at 11.55 fpe.  Unlike the older 56TH, the new one has a nice crown that is square to the bore.













Steve

[HectorMedina]

Very nice, Steve!

Thanks for the info.

Patience and Perseverance are two cardinal virtues.

;-)


Keep well, obviously I don't need to tell you to shoot straight, LOL!







HM

[Mossonarock]

Steve,
I just want to make sure I understand what you did with the two rifles.It sounds like you suspect the crown of our older D56 since you tested all your hardware on both rifles.

I'm really interested in hearing if you get the issue resolved because I hope it will apply to my rifle.  I'm also dealing with weird fliers with my D56 and I'm not certain what the cause may be. I've tried different springs and scopes but I still get >1 inch groups at 35m. I don't know if its my barrel/crown or if the sliding action has too much play in it because it does noticeably rock laterally. Heck, I don't know if its just the pellets but I'm pretty sure its not the pellets. I'm pretty sure its not me because I can get better groups with my HW97kt. I like my D56 and want to bring out its best potential.

[Nitrocrushr]

Steve,
I just want to make sure I understand what you did with the two rifles.It sounds like you suspect the crown of our older D56 since you tested all your hardware on both rifles.

I'm really interested in hearing if you get the issue resolved because I hope it will apply to my rifle.  I'm also dealing with weird fliers with my D56 and I'm not certain what the cause may be. I've tried different springs and scopes but I still get >1 inch groups at 35m. I don't know if its my barrel/crown or if the sliding action has too much play in it because it does noticeably rock laterally. Heck, I don't know if its just the pellets but I'm pretty sure its not the pellets. I'm pretty sure its not me because I can get better groups with my HW97kt. I like my D56 and want to bring out its best potential.

Hi Tim, Yes that pretty much sums it up.  My original 56TH that this thread was based on started out awesome with 1/4" groups at 50 yards.  I then started to see some occasional fliers and groups gradually started to grow.  I would say the largest were in the 1/2" range at 32 yards.  I did all kinds of testing trying to figure out what was happening;

Barrel cleaning
Stock screw torque
Sled torque
Pellets
Scopes
Box Testing scopes
Mounts (fixed, adjustable and Hectors Accurized ZR mount)
Changes in spring preload

I finally fixed my attention on the angled crown, thinking perhaps it was giving the pellets a little flip as they were exiting the barrel causing occasional oscillation in flight?  I gently hand lapped the crown but I think groups might have actually gotten worse after that.  While it did appear to make a change in grouping, I don't think it was for the better.

When I switched to the OEM powerplant with the JM spring and guide (14.5fpe), the groups were worse at 32 yards, closer to the 1" mark that you mentioned.  One thing worth mentioning, although I have not personally seen this, Hector feels that the heavy muzzle weight on the 56's can contribute to fliers due to them actually accentuating barrel harmonics.  Just something to consider.

As you can see in my post above, my new 56TH has no problems whatsoever.  This is a new model (made in 2018), manufactured at the Ense facility in Germany.  My original 56TH was manufactured in the Rastaat facility (including the barrel, which I originally thought may have been a newer Ense barrel)

The barreled action from my old 56 is currently on it's way to Hector.  He is going to look it over and see if he can figure out what is going on.

Steve

[Yogi]

Steve,

Great post!  Thanks for updating.
By "Harmonic Reducers " do you mean a well fitting muzzle brake/cocking handle? 
Or is there more to it?

Thanks,

-Yogi

[Nitrocrushr]

Steve,

Great post!  Thanks for updating.
By "Harmonic Reducers " do you mean a well fitting muzzle brake/cocking handle? 
Or is there more to it?

Thanks,

-Yogi

Hi Yogi, I was referring to a Harmonic Reducer that Hector makes.  It eliminates the heavy muzzle weight on the 56 and replaces it with a specially designed unit that tames the barrel harmonics on the shot, making for more consistent POI on target.  The barrel will always move/flex/vibrate on the shot.  As I understand it, the key is taming the movement and maintaining a consistent position of the muzzle at the time the pellet is exiting.  This is where Hector feels that the solid, heavy factory weight can actually add to the harmonics rather than working to tame them.


Steve

[subscriber]

or if the sliding action has too much play in it because it does noticeably rock laterally.

Can you set the slide so stiff that it can't move, then see what that does to groups?  In theory, locking the slide should shoot worse (that is why the slide exists).  Alternatively, rather than increasing the drag on the slide, is there an adjustment to reduce side play?

[subscriber]

One thing worth mentioning, although I have not personally seen this, Hector feels that the heavy muzzle weight on the 56's can contribute to fliers due to them actually accentuating barrel harmonics.

Is it possible that the muzzle weight is slipping position slightly on each shot?  So, not hard coupled with the barrel, and not always in the same position.

As an aside, I presume that you examined the piston seal for damage, such as scorching when you had it out?

[Nitrocrushr]

One thing worth mentioning, although I have not personally seen this, Hector feels that the heavy muzzle weight on the 56's can contribute to fliers due to them actually accentuating barrel harmonics.

Is it possible that the muzzle weight is slipping position slightly on each shot?  So, not hard coupled with the barrel, and not always in the same position.

As an aside, I presume that you examined the piston seal for damage, such as scorching when you had it out?

The muzzle weight is held into position by 2 set screws that settle into recesses in the barrel.  After they are snugged up, no sliding.  It has remained tight.

Yes, piston seals are good, both the o-ring and the parachute seal.  Remember, this same powerplant was tested in my new 56, along with an OEM powerplant.

Breech seal is also good.

Steve

[HectorMedina]

Steve,

Great post!  Thanks for updating.
By "Harmonic Reducers " do you mean a well fitting muzzle brake/cocking handle? 
Or is there more to it?

Thanks,

-Yogi

Yogi

There is MUCH more to it.

;-)







HM

[Mossonarock]

The barreled action from my old 56 is currently on it's way to Hector.  He is going to look it over and see if he can figure out what is going on.

Any updates yet? Or is it still too early to tell?