Huben Huben GK1 .22: A Beginner's Journey to a DIY Mini Carbine

[Navig]

So here's what happened next.

Even though I knew it was a thin walled prototype, I decided to go ahead and fire the pistol.

Well...in addition to the usual pellet launch sounds, there was a distinct, unmistakable, and concerning sound pop of plastic crunch.

So I took down my adapter for an autopsy:

As you can see there are crush fault lines from the bolt holes.
It only took a few moments of consideration to realize what occurred.
Consider: even though I have not disassembled this pistol, I have seen that one of the methods of degassing the GK1 involves an explosive blow out of the end receiver. Krazcool de-gas method.
Consider: Huben has assembled this area with fairly thick plate of metal attached to the pistol by 2 hefty M5 bolts.
Conclusion: part of the usual action of the pistol involves high pressure action at the end plate receiver.

By bolting an add-on to the receiver end plate, the receiver end plate then becomes a pneumatic hammer head on to your add-on adapter:

 

[longdog]

Andrew’s adapter fits perfectly and has held up to a couple of thousand .25 cal 875fps shots.
Why not just buy one of his and relax.

 

[Nutcracker]

If a man ain't careful, he may turn a gun into a two-directional weapon—one projectile out the muzzle and the other out the receiver aft.

I like to overbuild stuff. Comes from a fear of failure, LOL

 

[Nomadic Pirate 66]

I realize the beauty of making your own stuff but there's already so much proven aftermarket parts out there why bother ?

There's a point of diminishing returns.

 

[scottblair]

So here's what happened next.

Even though I knew it was a thin walled prototype, I decided to go ahead and fire the pistol.

Well...in addition to the usual pellet launch sounds, there was a distinct, unmistakable, and concerning sound pop of plastic crunch.

So I took down my adapter for an autopsy:

View attachment 448563

As you can see there are crush fault lines from the bolt holes.
It only took a few moments of consideration to realize what occurred.
Consider: even though I have not disassembled this pistol, I have seen that one of the methods of degassing the GK1 involves an explosive blow out of the end receiver. Krazcool de-gas method.
Consider: Huben has assembled this area with fairly thick plate of metal attached to the pistol by 2 hefty M5 bolts.
Conclusion: part of the usual action of the pistol involves high pressure action at the end plate receiver.

By bolting an add-on to the receiver end plate, the receiver end plate then becomes a pneumatic hammer head on to your add-on adapter:

View attachment 448564

Ahhh,,,I have my doubts that the back plate hammers backwards when the two screws are even, gently snug!!!!
I rather think you torqued the screws too tight, for your fragile print job...IMHO.
Just saying.

 

[Navig]

I think there is some energy coming out the back of the receiver.

Anyways, I hear you guys. This is not the "Here is the quick best way to P2C your GK1" thread. For sure, Moistone's product, or heck have you see the Buck-rail product--go that way. I would also be absolutely shocked if we did not soon have an official Huben GKarbine1. Obviously they follow the pulse of their products.

This is about the most inefficient way to mini carbine your GK1. Have I not mentioned that I am learning how to 3d model and print while I am doing this? But there is no diminishing of returns to me. Everything I'm doing along the way is teaching me, and I am loving it. I'm 100% confident Andrew would agree with me. It is so much fun to think of a thing, design it, have Christmas-happy-anxiety waiting while it prints, put it on my GK1, and fire pellets.

I don't think I've "misadvertised" this thread in any way. I think the jibe of it is very clear.

I am a beginner. I am posting my experience from the beginning. This is my journey to convert my GK1 to a mini carbine. Get on the train!

 

[Navig]

Considering what happened to my lame thin walled prototype, I felt there were 2 options:

1) Strengthen the print

or

2) ?Something else




1) Strengthen the print.

The first thing I would do to strengthen the print would be to print in 100% infill. Additionally, according to Prusa, the best strongest infill pattern is lines--I guess this virtually weaves the material.

The next consideration would be material selection. Here is where my novice 3d printing knowledge starts to slow down. Material selection influences print strength in 2 ways: properties inherent to the material and layer adhesion.
For example, a material's inherent strengths (and there are different types of strength--crush, tensile, etc) can be listed, based on a solid block of the material.
BUT, a 3d printed object is NOT a block of solid material--it has been laid down in a pattern of filament. And so how the filament adheres to itself is also very important.
The last component of material selection I mention is heat resistance. All of this material is laid down like a hot-glue gun, and so all of it has a liquid-conversion temperature. Additionally, you must consider bed temperatures. The first layer going down is obviously important, and if lifts from the bed, the whole thing is screwed--so the bed must be heated and kept at a particular temperature.

So, the starting material for all 3d printerists is PLA. Printed PLA is reportedly quite strong (inherent and adhesion), BUT brittle. Once it reaches its breaking point, it shatters. Also, it has a fairly low melting point--I print it at 210c (with a bed temp of 60c). Anyways, while I am unaware of any actual studies of such, this sound kind of like a bad recipe for this part. Where I live, in the summer it routinely hangs above 110f, and having a piece that might unexpectedly shatter inches from my face, just sort of sounds bad. On the other hand I had a discussion with someone that routinely prints powder-burning-pistol parts in PLA+ and uses them in 120f+ Arizona heat with zero problems.

The next obvious choice would be PLA+. Stronger better higher heat.

But most people would probably recommend starting with PETG. Stronger, more flexible, less shattery, prints at 230-250c, bed temp 80-90c.

At the higher end of strength, would be ABS and Nylon. I really don't know much about these materials, you would need a next level 3d printer with a heated enclosure.



I have only ever printed with PLA and PLA+. If you don't have a 3d printer, there are a coupla things you have to understand. There are a lot lot lot of settings, and there is a learning curve, and it is specific even down to your individual printer AND the brand of filament you buy. You end up doing a fair bit of test prints to get everything dialed in.

Stepping up to PETG involves learning several new curves.
First can your printer physically handle PETG. I believe technically it can. My Ender 3 v2: The max print temp is 260c, plus I have upgraded to capricorn tubing, and the max bed temp is 90c. To learn how to print properly in PETG on my Ender 3 v2 would probably take several weeks of youtube videos, and test prints. I honestly just haven't put in the time yet.
There is another problem with PETG--it is hygroscopic, meaning it absorbs water, apparently fairly voraciously. That would mean investing in or building a filament dryer device.
Finally, I am fairly certain Moistone prints in Carbon Fiber Reinforced PETG. The carbon fiber filaments added in might wreck standard print nozzles, so I would have to invest in upgraded nozzles.

I WAS planning on putting in the work to add PETG to my toolbox, when I decided to consider Option #2.

 

[Navig]

PS. I was going to say I knew this portion might ruffle a few feathers as there are good products already out there--but that it would only be for a few posts, and then I would be moving on. But honestly, the next thing I did after completing my version of an adapter block...was to make a stock from a broken ski pole. So yah...that's how this train rolls.

 

[sb327]

You keep doing you. There are plenty of naysayers on these platforms that are ready to pounce. Don’t let that discourage you.

There is definitely a significant amount of energy pushing the rear plate rearward against the screws. Putting anything between the screws and plate would place this energy into it as well. The good thing though, in this case, is that it is a compressive force. 3D prints tend to handle compressive forces quite well when they are printed at a higher density infill.

Keep on keeping on and sharing. You will learn a lot along the way and yes, it should be fun.

Dave

 

[wimpanzee]

I think there is some energy coming out the back of the receiver.

Anyways, I hear you guys. This is not the "Here is the quick best way to P2C your GK1" thread. For sure, Moistone's product, or heck have you see the Buck-rail product--go that way. I would also be absolutely shocked if we did not soon have an official Huben GKarbine1. Obviously they follow the pulse of their products.

This is about the most inefficient way to mini carbine your GK1. Have I not mentioned that I am learning how to 3d model and print while I am doing this? But there is no diminishing of returns to me. Everything I'm doing along the way is teaching me, and I am loving it. I'm 100% confident Andrew would agree with me. It is so much fun to think of a thing, design it, have Christmas-happy-anxiety waiting while it prints, put it on my GK1, and fire pellets.

I don't think I've "misadvertised" this thread in any way. I think the jibe of it is very clear.

I am a beginner. I am posting my experience from the beginning. This is my journey to convert my GK1 to a mini carbine. Get on the train!

I appreciate you sharing your process and journey for this!

 

[Nutcracker]

There is nothing wrong with making your own stuff, and trial and error are part of it. Regarding cost-saving, buying an already-made, proven product is probably more economical, but some people prefer the challenge. Thanks for sharing your failure, some people leave that part out.

 

[scottblair]

PS. I was going to say I knew this portion might ruffle a few feathers as there are good products already out there--but that it would only be for a few posts, and then I would be moving on. But honestly, the next thing I did after completing my version of an adapter block...was to make a stock from a broken ski pole. So yah...that's how this train rolls.

I appreciate what you have stated here. Makes more sense to me now. My comment was too hasty.
My apologies.

 

[kkarmical]

I think there is some energy coming out the back of the receiver.

Anyways, I hear you guys. This is not the "Here is the quick best way to P2C your GK1" thread. For sure, Moistone's product, or heck have you see the Buck-rail product--go that way. I would also be absolutely shocked if we did not soon have an official Huben GKarbine1. Obviously they follow the pulse of their products.

This is about the most inefficient way to mini carbine your GK1. Have I not mentioned that I am learning how to 3d model and print while I am doing this? But there is no diminishing of returns to me. Everything I'm doing along the way is teaching me, and I am loving it. I'm 100% confident Andrew would agree with me. It is so much fun to think of a thing, design it, have Christmas-happy-anxiety waiting while it prints, put it on my GK1, and fire pellets.

I don't think I've "misadvertised" this thread in any way. I think the jibe of it is very clear.

I am a beginner. I am posting my experience from the beginning. This is my journey to convert my GK1 to a mini carbine. Get on the train!

Do you mind sharing your printer set up.
Thinking about picking up a 3d printer not for making stuff for my pistol, but more so as something that may be able to provide interest for my son, since they have classes at the school the wife teaches at.

And yes of course I have ulterior motives, it'd be great for me to just be able to ask him to make stuff for me win/win..

 

[Navig]

Thanks all! We are all here because we love the shooting the GK1! I can totally see how people on this thread would be like, man just get on with it so you can be actively shooting! Don't worry, these posts lag behind where I am at by about a month. It takes me about an hour to prepare each post, and like I have mentioned, this is hobby for me (ie I am not being paid to generate content), so I am taking my sweet time to post stuff. I am using the pistol much more than I think this thread pace implies. Skip to the happy ending, I do have a fully operating mini carbine made my way, and am even at the stage of testing various home 3d printed moderators.

@kkarmical I am using a self upgraded Creality Ender 3 v2. It's the only I've got so I can't really talk about other printers. I bought it with the understanding that it is a barebones machine ready for troubleshooting, learning about 3d printing hardware, and upgrading.

If you/your son wants to focus on designing 3d stuff and having an end product, like a 3d printer is a bake-a-cake oven, this is NOT the machine for you.

This is the machine you want if you want to learn about 3d printing machines--Ima read between the lines for you. Something will go wonky, then you will watch a youtube video (of which there will be many because so many people have this machine), and then you will fix it. Eventually you will have the confidence to understand how all the parts will work. And once you dial it in, then you will realized that you want to upgrade something on it. And then you will buy the upgrade. And repeat.

Just to throw it out there. If you should buy it, right away purchase upgraded bed springs and a flexible magnetic bed. After about a month you will want to buy the autobed leveling system. At some point, you will want to change out the shrieking banshee fans. Then at some point (where I am at), you will want to step up the next level upgrade, a direct feed hot end.

I know I am not doing a great job of selling this machine, but I am definitely glad I bought it and have learned from it. Folks that have paid higher money for more advanced machine often freak out if something goes wrong with a print or the machine. People that have learned on a machine like this are just like "Just fix it".

I do feel non-sale price for an Ender 3 v2 (or equivalent) is kind of high for what you get. I picked up this machine for something like 40-50% off on Amazon Prime Days. I think I got it for $120.

 

[Navig]

I do my design work on Sketchup pro, which is not generally the chosen tool. Sketchup is more for architectural work. But it is so easy and fun to use, and there are so many resources out there. For example, when I was designing my fill port plug, I literally just googled "Sketchup how to make a dome", and 3 youtube videos pop up.

I print with the Creality Slicer that comes with printer, which is just a modified Cura Slicer program.

 

[Navig]

Option#1 Print it stronger

To summarize: To make a strong mounting block I would at the very least recommend a solid print of PLA+. And don’t ignore any lube leaking from this seam:

 

[Navig]

Option#2
I’m going to try something else!

My thought was this: I am just looking attachment points for an adapter block. I considered: is there a way to have this be a M5 screw, but also be an attachment point:

The answer: Threaded standoffs!

 

[Navig]

Side excursion:
My main background is in building custom PC cases, from scratch, and we do this all the time in modding. Motherboards are typically mounted using a threaded standoff.

Standard motherboard standoffs, typically M3 or 6-32.

The standoff screws into your motherboard tray. The motherboard lays on top of the standoffs. Then you screw a securing screw to hold the motherboard down on to standoffs.

Video demo here.

So I scoured the internet, and ended up at my usual shopping site for all things hardware, Mcmaster Carr.

M5 threaded standoffs.

Ordered up a set, as well as some M5 mounting screws.

 

[Navig]

And here was the plan:

The M5 standoff replaces the stock M5 screw--the standoff portion acts as the screw head, holding the endplate to the pistol. All metal all strong. The endplate takes all the air pressure just like the stock pistol.

Now my adapter block gets attached to the backside of the standoff with the mounting screws. The block takes no pneumatic hammer--it is only subject to the forces of staying attached to the pistol and transmitted from whatever attached stock you choose thru the picatinny rails.

 

[sb327]

I had considered a stand-off type approach when making my stock adapter. I’m certain it will work but since my adapter is machined aluminum, I really didn’t need it.

Fwiw, I don’t think you will need it either with a full infill print. The force, while significant, is buffered by a spring/buffer. Meaning that it’s not as shock loaded as it seams.

Keep in mind when changing hardware that the gk uses alloy screws here which may be significantly stronger than some of the standoff screws that are available.

Dave