A custom bullet mold for Huben K1

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Hi. I did not get a chance to shoot those yet, as you said, they do not make them anymore.... Thank you for your input. Huben seems to shoot well as long as the bullets are as tight as possible in the barrel.
BTW: my pressure gauge on the Huben is off by abaut 30 bars. I have it set on 170 bar on the gauge but in reality it is only 140 bar... I assume you have the same situation...
 
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Hello!

Thank you all for your inputs.

I am happy to let you know that I have a successfully mold prototype. The boat tail did not give good results so I vent for a more traditional approach. The most accurate shape will have 36 - 37 grain (depending on the alloy) and BC 0.14. The BC was measured with two chronys at 70 meters. The velocity drop was from about 295 m/s to 270 m/s. So far I got better than 2 MoA groups without sorting the bullets. The ideal velocity for them seems to be around 300 m/s or just under. Huben's regulator needs to be set at about 155 bar (my gauge is showing 180 bar at this pressure because these gauges are not accurate) and the power wheel fully opened. I was using direct swap (the barrel has exactly the same external dimensions as the stock one - you will see in the video) barrel that Rojal offers for these tests. I will also test soon with my semi bull barrel as well as the stock barrel. I am pretty sure that with stock, the velocities will be lower because of the choke...

That is it for now, I will release a video on youtube in about two weeks (this weekend I am going to IWA).

PS: I will also meet with Huben at IWA. If you have any questions I can ask and maybe get an answer...
 
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Another thing...

I have alos arranged with MP molds to offer these molds. They will probably come in these options:

Brass 6 cavity option
Aluminium 8 cavity option
Sizing set that fits Lee presses

The molds will come in 2 dimensions, one for using without sizing, the other for using with sizing....
Sized bullets will of course produce greater accuracy.

I will inform you when these options will be on the MP mold website...

https://www.mp-molds.com/
 
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Nice video Gregor!
Good luck at the IWA, I hope that you can build a good relationship with Huben, and find out where they got those cast bullets they used in the first video i seen. It may be better if we can purchase them from their supplier. https://www.youtube.com/watch?v=g_fDRnyI7go.

My Huben still has not arrived that I ordered in September. I called Mike with Mrodair at the end of January, and he said that because of the Lunar New Year no one was working in China. The New Year was over the first week of February, still no Huben! ;o(

Let us know how it went with them, we all are interested in more info!!
Cheers My Brother!
 
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Hello Gregor,
So you have made your molds. this is very fast, I still testing and examing my pellets.
It looks Very good pellet for 70 Meter and looks very accurate with your custm barrel. The B.C of 0.85 is amazing for the 70 Meter that means it will be around 0.9-0.95 in between 100-150 meter or maybe more", but I noticed the lighter pellet is flying up and right , yes it is faster but the change of velocity was very small to show this dramatic change up word and right I understand upward it is lighter it is faster by 1-2 meter or 3-6 feet at muzzle , but why to the right the the lighter the pellet the faster it is and the pellet has more round perminutes but even for 3-6 feet faster it should not show this much of change to the right, I believe this change is an early indicators for yaw of repose. My advice to film the pellet flying for the 70 Meter and to shot the pellet for a 100, 150 and 200 meters just to check the flying of pellet not the for accuracy. Try to Shot on paper, then measure the hole size vs pellet dimensions, also check how many inches it was off from the poi, corelate the results with the wind speed, angle and Bc of the pellet after that check the compensation calculation, was it equal to expected calculation or it was more than expected. Remember the barrel with Righthand twist will go downward and right more than expected for the same pellet weight and the left hand twist will go upward and left more than expected for the same pellet weight.

Your friend
A.Mathekor
 
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Aj: I am using NAA CBB as well just like you said by sizing them with my sizing die.... The are very accurate, but the power has to be lower and the BC is not as good as with my bullets.

A.Mathekor: Hi. My bullets have BC of 0.14. That makes them perfect for ranges bigger than 150 meters...Unfortunately I don't hat a range that long :(. It is normal that different weight pellet have different POI. This is not because of the velocity (at least not at relatively close ranges) but hast to do with the vibrations on the gun as they exit the barrel at a different time and the barrel is pointing at a different direction... This is normal for airguns, especially for springers and also for high power PCPs... This is also the main reason why unregulated airguns are less accurate than regulated. Most people think that the problem is in the change of the velocity but it is actually in fact that different internal stress occurs at the time the pellet leaves the muzzle...
Than you for the suggestions, I will do that if I find a longer range :). I agree about the effect of the righthand twist on the long range impact...
 
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Hi Gregor,
For my calculation the velocity at muzzle then at 70 Meter is around 0.085 I did some correction for your altitude 😉, about the vibrations you mentioned I believe I knew it as harmonic, Simply add weight to the barrel. Do you recall we discussed the barrel twist and barrel harmonic on May last year also If you recall you were telling me my projectile has impressive B.C, but I answered you I need it to be accurate with half the given b.c.
The hall mark of projectile design is to have the most accurate pellet for upto 200 meter with down grade energy of 27ft.lb (36.61J), So the lightest pellet with the highest accuracy and B.C. the limit for weight is <27grain, B.C IS >0.9 the accuracy must be less than 2" (50mm) at 200 Meter so I can humanly hunt the deer with excellent head placement.

"Day Dream😌 day Dream 😌day Dream😁"

Now coming bak to your projectile it is a real deal try to Shot them at 250 Meter/second with adding weight to barrel. If it is not working make it shorter from the base.

Wish you good luck
A.Mathekor
 
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Not sure if I understand you correctly. Are you talking about my bullets? If so, then I think you are mistaking. If you calculate 298 m/s at the muzzle and over 270 m/s at 70+ meters, the BC is around 0.13 to 0.14... My altitude is not that high to have such a significant impact (I am at around 250 - 300 m above sea level)... Not sure how you got your numbers, but I can tell you that JSB beast has roughly that BC and when I was shooting with it at 325 m/s, the velocity was under 270 m/s at 70 meters...
Regarding vibrations; it is not always harmonics that is the problem, sometimes it is simple the face that airguns "move" before the pellet leaves the barrel, but in most cases harmonics amplify this effect.
I remember telling me about you bullet, yes...
I have a lot more to test with these bullets, but even if they shoot worse at all other settings / velocities, they are still the perfect choice for Huben at long range...
 
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That explains it... I was mumbling in the video... Initial was around 298 m/ s, and the velocity at the chrony was around 271 m/s. There were two shoots when it was lower (265 m/s), not sure why but considering that most of the shots was over 270, I went with that number... Initial velocity was about the same as in the previous clip...
The last two clips were made with Rojals custom barrel, the fist two shoots were made with my custom barrel. My barrel is lightly longer, that is why the velocity was slightly higher...
 
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