Huben Hammerless K1

wlbryce, may I ask what is your pellet of choice for "dead on at 50 yards"? and what is your preferred usage for the gun? Your satisfaction with it's accuracy in your preferred shooting range piques my interest (again), especially with the features of quiet operation, the high shot count, and energy nearing the .22LR.

wlbryce, I see that you use this gun for pest control, and have the Predator as it's food of choice. With that, I believe people can have a little hope that a bit of adjustment and fine tuning, along with some pellet sorting, might yield some acceptable results with heavier pellets. It's a small wonder that the Predators haven't caused a loading issue by the tips being loosened in the process. I guess the design works well in that regard. Congrats on an interesting piece.  
Do you know if the loading air pressure is variable\adjustable? Just an idle curiousity. 

wlbryce：
First I want to thank you to do such a job,let all of us know about it clearly.

U r much more honest than Chinese People,Chinese Society is full of cheating now,I won't believe any business man immediately of what they said ,just like HD MASTER said that he shot much better than you did,I won't believe that.They are less of honest and trustworthy. 

Back to what I want say is that what I told you here,some of them is what HD MASTER said(I have pictures,but I don't know how to upload it) just like the grooves was made in the magazine,he told me that and I just imagine its function and how it works.If I was wrong,I apologied for the misleading. 

I want to tell u all about how the valve works,its diameter is about 8mm(HD told us,about 8mm,maybe 8.2mm,I forgot it),and when it is released，it moves about 9.5mm(Also HD said，I forgot what he said,only remember that it is less than 10mm),and what is the energy it gets from the air pressure,I can calculate for you:

F=PS
P=15MPa=15*(10^6)
if the Constant Pressure Valve was set at 17MPa and when it was released the pressure maybe will go down to 13MPa
I use the average (17+13)/2=15MPa
Of coz the pressure decline is not "linear",I can only use the approximate method to get the average one，I think it won't be a big deviation.
S=pi*r*r=3.14*4*4*(10^-6)
then the F=15*3.14*4*4=753.6N
W=FS
then W=753.6*0.0095=7.16j
If we ignore the Friction Force of the Valve

And a traditional PCP that is working within a spring and a hammer,what is the energy the hammer got from the spring???
The spring max force is about 50N and we suggest that at last the force is zero.
So the average force is about 25N because of the spring force is “linear”--------Fspringforce=kx
And how far dose the hammer move?about 20mm,yes it is nearly double of HUBEN's 9.5mm.
But what is the energy the hammer got from and at last the energy was used to open the one-way valve?
Then,W=FS=25*0.02=0.5j

When the HUBEN released the valve,it got 7.16j（the internal force is much more powerful than the traditional one just like FX cyclone） and at last it will hit something and stop,obviously the structure inside HUBEN needs a buffer part，I mentioned this problem and HD MASTER answer me that there is a polyurethane part to absorb the energy,but I m wondering again,what will it become to when it was hit thousands times because it can only reduce a part of the hitting force.I have ever seen that HUBEN said that it needs no service,how could a company say such confident words???Dose Apple ever said like that?Is it arrogant？Who else can say that my product will never go wrong???Or I misunderstand about “never need servicing”?

Forgive my poor English,I haven't used it for a long time since my graduation from the school...

http://e.picphotos.baidu.com/album/s%3D1100%3Bq%3D90/sign=395920e386cb39dbc5c06357e0263255/37d3d539b6003af3de1a9869322ac65c1038b613.jpg


Hope U can open this address and this might be the operate mode of the valve，I failed to upload it.

I have been unable to access the photos from River Devil's post but I can imagine the structure of the Huben valve working from the Patent Drawings and also because in my home workshop I have a prototype airgun that works in exactly the same way, except that I do not need the constant pressure valve so I do not infringe the Huben Patent.
The forces on the firing valve are much more complicated than River Devil's formula would suggest and I would not expect the power dissipated in the movement of the valve to be anything like as high as he suggests.
Remember that the Huben valve is a double ended spool valve, a smaller end of which closes the port leading to the magazine and a larger end of which is slideable in the valve housing. The smaller end would not need to be any larger than the bore of the barrel so we can guess that that is about 5.5mm. Therefore it is the other end that is about 8mm. Thus in the static state the gas pressures on the two ends will partially balance one another and the resultant force need only be sufficient to overcome the force of the return spring and the friction on the valve. When the valve is released the force will stay the same during the initial opening movement until the port is fully opened and the balancing effect of the front end of the valve is lost. But then the pressure will be dropping in front of the valve and the force on the valve will depend on how fast the pressure drops and how fast the valve moves. The mass of the valve is relevant here but we don't know what that is.

Lbl25a:
Thanks for your detail explaining.In fact,I can only understand a part of them.
And because of my poor English,I can't describe it clearly.Sorry for that.
I'v said the HUBEN might borrow something from Steyr LP50,a 5-shot-semi-auto pistol.
May I ask that if one of the "double ended spool valve"is just like the LP50's valve behind the pellet???
According to LP50,I mean that when the valve was hit by the hammer and the gas was set free,and it at last blowing the pellet into the barrel,but that moment,it also blows another valve which is coaxial to the barrel(yes,it is behind the pellet) back and made a second cocking,and waiting for another shot.

Back to HUBEN.
I imagine that when the valve opens,it first push the 8mm valve out because of it needs to set the gas free,than when the 8mm valve was opened,it would blowing the pellet into the barrel and the same time it will push the 5.5mm valve behind the pellet to go back and it has 2 works to do:
1.Make the magazine work by a mechanism.
2.Push back the 8mm valve to the original place and finish the next cocking by another mechanism.

Replacing(Close) the 8mm valve needs a complex structure and it seems that the designer should calculate the force of lever and maybe anything else,it is really a complex work,but I don't care about this,what I just want know is:
1.Accuracy
I always think that it is the most important thing of a sniper gun and also blowing pellets is extremly hard to control the accuracy and the HD MASTER ever admitted that its accuracy won't be very good.
It is decided by the structure,you should never compare it to Steyr LG100,that is a field target air gun.
2.Durability
Nobody wants to buy something always needs repairment,complexity means troubles.
I knew several Chinese players whose FX Revolution(Monsoon) goes wrong and they have no capability to repair it.

Sorry River Devil I can't comment on the Stehr LP50 as I don't know this gun. I think that it is hammer operated in which case it is quite different from the Huben. The Huben valve is quite simple it only opens and closes. It is only connected to the sear that releases it to open and the return spring that closes it when the pressure in the barrel drops below the setting of the constant pressure valve.
Since the valve is self resetting the only thing that is necessary for semi auto action is for the magazine to be indexed. I assume that this is achieved by bleeding air under pressure from the barrel, which would not waste much energy. Recocking of a hammer valve can be achieved In the same way but would waste much more energy.

 Thank you for the continued updates. Lot's of good info and pictures. 
Personally "I" likely will never need one, not really "my" thing but it has it's own cool factor ( love the old crosman 600 and people pay up to $600 for a reworked- longer barrel & "hot" valve & paint) so it seems it would be a value to many folks. "I" though the very first groups you posted were outstanding given all the facts , new design not included,
with the pellet used and over 1,000fps, number of shots fired for target, a DARN good hunting group, what's to complain about? 
Looking at all the pictures ( and I found some more else where showing slightly more disassembled parts, not sure who posted them elsewhere) it doesn't seem service would be all that bad once accustomed to it. Not as easy to clean the barrel as some but barrel cleaning on a very smooth - hand lapped- barrel if you use say clean JSB pellet really doesn't need to be done often at all.
The "blow through the revolver cylinder" thing should work alright and your groups are MUCH better than say the ARS 6 dul / resurrected by evanix "double action" pistol and rifle copy, and, the huben is simi-auto and folks purchased the exanix and were happy with 6 or so shots all dropping in velocity, this rifle beats the heck out of that one.
Ten years ago a company could have sold ton's of these as is, out the door no further work and people would have raved. Not sure whats changed. Can a $2,000- $4,500 BR airgun shoot better groups, well yes it likely would be it is a TOTALLY different beast.
I do know one BP guy that will be his first pre-charged airgun the day these hit the US, it is exactly what he ( and likely many more PB types like him) have been waiting for.
Note: while I wouldn't buy one I certainly would like to try one and wouldn't thrown one out if someone gave me one.

Keep us posted.

John

Great, Wlbryce; glad they're showing promise. Fascinating that the groups tightened up at slower velocity; as I noted in my email, Tom Gaylord posted a couple of years ago that the Piledrivers would require 1100 fps to stabilize. But they also shoot pretty well out of my Marauder at slower velocity as well.

Could the key here be mass (My theory is that there are fluctuations in the valve opening of the Huben creating pneumatic resonance waves that are changing from shot to shot and the larger mass of the 30 gr Piledriver is helping to dampen these pressure waves before exiting the barrel. It would explain why lower velocities yielded better groups; more barrel time for the waves to stabilize.). I know they will be expensive, but I would test the theory by ordering out 40 and 45 grainers from Mr. Hollowpoint in the appropriate diameter: http://www.mrhollowpoint.com/6722.html

Keep up the good work, amigo.

I'm terrible with names and therefore I have forgotten the name of the really nice guy I spoke with from topgun-airguns. He was saying that he felt that the original barrel was too thin and light and the harmonic vibrations coupled with a slightly to large of a diameter bore was playing with the accuracy of the gun. I wonder if the lower pressure could equate into less harmonics on the barrel as well as a more "comfortable" velocity for those pellets -I don't recall what the twist rate was for the Huben but that could also be a factor for that weight and profile of pellet. Be interesting for Huben to get around to it and get those re-barreled guns out. 

Another thought occurs to me, Wlbryce. I hunted exclusively with handguns for almost 40 years. Back when I started there were no manufacturers making decent hunting loads so I cast my own bullets, worked up my own reloads, and learned to accurize my revolvers and semis. My standard was that any revolver or auto had to be able to group 5 rounds inside 2" at 50 yards. Two of the tricks I used on revolvers were to firelap the barrels (load mild loads with cast bullets lubed with lapping compound) and shoot them until the barrel was mirror smooth, and secondly to recut the forcing cones to 11 degrees to allow for slight variances in barrel/chamber alignment using a hand reaming tool from Brownell's: http://www.brownells.com/gunsmith-tools-supplies/handgun-tools/barrel-tools/chamfering-tools/11-deg-38-45-intermediate-chamfering-kit-prod26161.aspx

A couple of questions. Have you marked the chambers of the 19-round magazine and tried firing groups using a single chamber (would test the theory of whether there is an issue of cylinder/breech alignment.)? Secondly, is there an O-ring between the cylinder/magazine face and barrel breech? If you test fire a group using a single chamber and find that it eliminates flyers and there is no O-ring, then the solution might be to ream the barrel breech to a slightly wider taper.

I wish I was not so chicken to take this gun apart! I like shooting it so don’t want to end up with a gun that does not shoot after I figure out how it works! -wlbryce 

Chicken schmicken! That's your baby and you have been having a lot of fun with it, you really like it. I would feel horrible if you wrecked your baby to satisfy our curiosity. Discretion is the better part valor. 

attn Scotty: You mean Peter (Petr) of TGAG. He may have a point with the barrel being too thin to handle the power, as you've mentioned. So maybe reducing the fps even more might reduce the (un)harmonic vibrations of the barrel and perhaps stabilize the barrel a bit more? OTOH, I hope Huben sends WlBryce a properly sorted replacement barrel, and instructions on how to install it!
WlBryce, who can you turn to for servicing your K1? MrodAir is the only importer I know of, but Petr of TGAG is very good at repair work.