A custom bullet mold for Huben K1

I looked at these and they are a similar design as the Varminter, but more rounded nose and not HP's. I didn't see the length on the website.
When you mentioned that it is more like a revolver that made me think about how the rounds enters the barrel. If it is a loose fit then the accuracy may never be there, and the only way you to get it is to have a slight interference between the bullet and barrel, so the barrel will straighten it out during flight. Maybe .0005 larger than the barrel so the round makes full contact.
The other thing is with the max length of 11mm, there will be a finite weight that can be achieved with the 5,62 dia. and 11mm length. At these velocities we will need a heavy round to bring the fps under 1125, so we are below the sound crack, and have max ft-lbs of energy.
This is what I need for Hunting, and looking forward to the semi auto design of the huben, hopefully we can figure this ammo issue out without too much out of pocket.
I should be receiving the cast bullets soon, so I will let you know the length, and Dia. unfortunately I can't test them, no Huben!!! 

I am not sure how long the cast bullets are, if any of them are 11mm or less will send you some, and I will order some of those CBB++ and send them as well.
What is your email, I will get contact info. from there

Good to look on your cooperation . Did you see Rsterne work ?
http://www.gatewaytoairguns.org/GTA/index.php?topic=36813.0

Hey Gregor,
How's your work on the bullet molds coming?

Gregor, you might want to try these:

https://drummencustomguns.com/en/pellets/793-dab-airgun-ammunition-223-415-rn-1000.html?search_query=223&results=108

They are very common in The Netherlands for the Drummen Sinner airgun, and made for the 223 barrel.
They also have Eley Wasps.

regards,

Gijs

Thank you for the up date Gregor! Its very much appreciated, and keep up the good work man.

Has anyone tried these in the huben? point.http://m.ebay.com/itm/22-Cal-PDG-Destroyer-SAMPLE-26gr-hollow-point-25-heavy-air-gun-pellets-/261831286917?txnId=1915816053016&fdback=2
I picked some up but I dont get my gun for another month or so.

Sized some of the CBB bullets to .2195, seemed lkie as much as my choked barrel would take. (Had a bit of a hang fire at shooting at reduced power for easier pellet capture, about a 1/4 second delay between launch and clearing the choke.} Driven through the sizer nose first, the trailing portion showed uneven finish to the rifling marks. Sized skirt end first, looks to be cleaner finish of the rifling engraving. Loose in the magazine at this size. No winners yet in the accuracy department, but more testing to go.

A mold for casting .22 arrived today. 22lrreloader.com/design-details
The shorter cavity makes 25 grain, measures .217-.218 at the forward flanges. I intend to tool the mold to add a flange at the trailing edge about .224 to locate in the cylinder. The idea being that at firing, the last flange gets folded back making a bit of a skirt. We'll see how it goes.

Unfortunately I trashed the mold, my ingot of 'lead' turned out to be zinc. Mold got beat up in the demolding. Tooling to create an extra flange worked ok, but takes a hot pour to fill right once the zinc was replaced with lead. I might get another mold, but first I'm going to try some pellet skirt resizing.

Promising modification of the CBB cap and ball bullets:
1. size down to .217 in a die cup end first using a cup end punch to push on the bullet nose
2. flare the cup end out past .228 by standing on a flat plate and driving down with a punch conformed to the bullet nose
3. size the flared end down to .228 in a sizing die
Finished length runs.299 +/-.001

Despite the cheesy setup- some dings on the noses, the possibility of tilting the base in the flaring process-- I got a one inch group of five shots at 30 yards that included three holes overlapping, shooting bucket and sticks. (Sorry, no longer range at home.) Regulator at 15 mPa, adjuster open 21 clicks.

The heavy flare at the base locates the bullet securely at the breech end of the cylinder, giving a concistent power cycle, and extends the baseline to limit tilting off axis. Driving point end last in the initial sizing also extends the baseline.

I'm not saying this process is worth doing regularly, but it may indicate a desirable form.

Photos: unmodded bullet, modded, modded and fired into a phone book at 45°; the group and a modded bullet for scale.



edit:better quality pics of same pellets:



Pellets seem to lengthen 5 thousandths on exiting the barrel. Substantial leadding of the barrel encountered..

Hi Gregor,
Firstly I want to thank you for your very informative and helpful videos on YouTube relating to the Huben K1, excellent!
I have ordered my Huben K1 and expect to receive it in the new year. I live in South Africa and would like to let you know that I am very interested in your custom 5.5mm 40grn mould, so please continue with your development.
I am aware of a company called African Air Ordinance that have a custom 5.5mm mould for sale, and see that it is a flat base, and can be manufactured to any lenght or diameter. They have a 40grn bullet/pellet that is 11.5mm long, however it can be changed to 11mm long, which will give you about a 38 grn bullet/pellet.
Take a look at the following: http://www.africanairordnance.com/424820687/product/2025131/5-5mm-40-grain-round-nose-bullet?catid=625380
I have ordered 100 x 34grn pellets, ready to test in my new K1.
May I ask, if you are still impressed with the Huben K1?
Regards Malcolm

Hi Gregor, unfortunately for me, I have to stay below 5.6mm due to South African firearms regulations. If the caliber is 5.6mm or above we are only allowed 8 joules without a firearms license, however if the caliber is 5.59mm or lower there is no need for a firearms license no matter what the energy is, so I will keep below 5.6mm.
Are you still impressed with the Huben K1?

Hi Gregor,

first thank you for all the information you put on the internet about the huben. I would be more than interested in a custom bullet mold. Anyway today I have tried some wasp magnum .22 in my huben which I got from my local gun store. As far as I am concerned they do not sell these bullets anymore at their gun store and they had this open tin for a long time on their test range which I could have. At first when I measure the bullets I did not think they would fit in the huben cause they are 5,65mm in diameter but when I tried they do fit in the magazine just like you said they do. I don't know if you have tried these bullets but they seem to work well in my huben which has a replacement barrel to.
Btw here a small summary of the specifications of the bullet.
wasp magnum .22
5,65mm in diameter
9,20mm long
30.2grain
Distance I was shooting was 25 meters. First group of 3 where at 267m/s 11MPa, second group of 3 at 288m/s 13,5MPa. I will test them soon at 50 meters and with an other scope so I can see my target better, and maybe with other adjustments on the huben. However I need to be thriftily because I have just a few of these bullets left and I don't know were to find these bullets for sale. Here are some pics of the bullets and groups I shot. (btw MPa should have been bar)