Huben All Things HUBEN GK1 (air pistol) - Master Thread

[.177Guy]

Man… @500 fps I m squeezing no less than 8 mags Using 7ish grain ammo,
i am slowly realizing why some users love
unregulated pcp’s
i can dial down to 5 yds and have like 150 shots in one fill and I can go 800 fps and shoot 34yds away just by dialing the reg pressure screw,
which I would not dare do to my regulated pcp’s…
excuse my excitement as a newbie pcp user.

 

[WobblyHand]

What BS is this I hear about seating? Never seat anything! If you do, you are inviting a jam. Pellets are retained by the chamfer at the rear end of the magazine bores. The skirt is about .010" larger than the pellet head. The pellet head is a slip fit in the magazine's bores and the skirt , being a bit larger, is captured in the chamfer. This prevents the pellet slipping forward and jamming the magazine the same way a revolver cartridge is retained in the cylinder in a powder burner by the brass case flange. As to slugs, they have no skirt and must be retained by friction alone. The GK1 is NOT designed for slugs. You should not use them, they add no value at pistol distances and they cost a great deal more to shoot.

I've never seated pellets and they seem to work just fine. Can't see a need to seat them.

Can you back up your statement about slugs and the GK1? What is your source? Or is it just your opinion? Your tone is implying some authority, but without stating a source, well, it's just hearsay. Can you provide a picture of this "chamfer" in the magazine? I don't recall seeing one on my V3 GK1. Do you have a V1 or V3? (Vaguely remember it's a V1.). I do recall the magazine is grooved/rifled, but it's much shallower than the barrel grooves. Don't remember seeing any obvious chamfer, perhaps you are saying there's a taper? That's possible, but I don't know why Huben would do that.

Slugs can be cast for about 1.44 cents each in material cost, assuming $3/lb for lead, 85% yield, and 28.5 grains each. One can buy lead for less, I found an offer for $129/49lbs with shipping. Commercial slugs are expensive, often over 10 cents each. Decent pellets in heavier sizes are not cheap either. I don't know, but I paid more per pellet for the Norma's (even on sale) than for my cast slugs. Cost was a motivation to cast slugs. I tried casting 17 grain wad cutter pellets and my yield was less than half. It's tough to keep the mold hot enough for complete fill! Slugs are a LOT easier to cast.

NOE 217-30-FN-BJ5 slugs have a 0.217" body and a 0.2205" drive band. They work just fine in my GK1. And they are cheaper than equivalent weight pellets. No jams, at least for the couple hundred I've fired to date. If mine are doomed to jam, when might I expect to see that?

 

[WobblyHand]

Man… @500 fps I m squeezing no less than 8 mags Using 7ish grain ammo,
i am slowly realizing why some users love
unregulated pcp’s
i can dial down to 5 yds and have like 150 shots in one fill and I can go 800 fps and shoot 34yds away just by dialing the reg pressure screw,
which I would not dare do to my regulated pcp’s…
excuse my excitement as a newbie pcp user.

The GK1 can be turned down quite a bit. When I added the shroud I turned down the power, simply to make it safer to service (in case I screwed something up). My first 3 shots were 470 FPS with a 17.6 grain pellet (8.5FPE). Was pretty quiet with the shroud.

I soon turned it up to 960 FPS for the 17.6 gr pellets (36FPE). Then I switched to my cast 28.3 grain slugs (without changing the power adjust screw) and ended up with 838 FPS avg (8 shots) at 44FPE. Shroud is still effective down to about 15 MPa. Below that the valve dwell seems to be comparable to the pellet transit time. That means it gets louder. So shooting at 32 MPa was significantly quieter than at 15 MPa.

 

[steve-l]

I've never seated pellets and they seem to work just fine. Can't see a need to seat them.

Can you back up your statement about slugs and the GK1? What is your source? Or is it just your opinion? Your tone is implying some authority, but without stating a source, well, it's just hearsay. Can you provide a picture of this "chamfer" in the magazine? I don't recall seeing one on my V3 GK1. Do you have a V1 or V3? (Vaguely remember it's a V1.). I do recall the magazine is grooved/rifled, but it's much shallower than the barrel grooves. Don't remember seeing any obvious chamfer, perhaps you are saying there's a taper? That's possible, but I don't know why Huben would do that.

Slugs can be cast for about 1.44 cents each in material cost, assuming $3/lb for lead, 85% yield, and 28.5 grains each. One can buy lead for less, I found an offer for $129/49lbs with shipping. Commercial slugs are expensive, often over 10 cents each. Decent pellets in heavier sizes are not cheap either. I don't know, but I paid more per pellet for the Norma's (even on sale) than for my cast slugs. Cost was a motivation to cast slugs. I tried casting 17 grain wad cutter pellets and my yield was less than half. It's tough to keep the mold hot enough for complete fill! Slugs are a LOT easier to cast.

NOE 217-30-FN-BJ5 slugs have a 0.217" body and a 0.2205" drive band. They work just fine in my GK1. And they are cheaper than equivalent weight pellets. No jams, at least for the couple hundred I've fired to date. If mine are doomed to jam, when might I expect to see that?

I have a V1 and V3. That chamfer is obvious just look, you'll see it. If you doubt my statement, get out your pin gauges and calipers then measure yourself. If you still cannot see the chamfer, remove the magazine and reverse it. Then try to load something. You'll figure it out pretty quick. As far as oversize drive bands on slugs, they provide the required friction for retention, as stated. Still, slugs add no value at pistol distances, why shoot them?

 

[WobblyHand]

I have a V1 and V3. That chamfer is obvious just look, you'll see it. If you doubt my statement, get out your pin gauges and calipers then measure yourself. If you still cannot see the chamfer, remove the magazine and reverse it. Then try to load something. You'll figure it out pretty quick. As far as oversize drive bands on slugs, they provide the required friction for retention, as stated. Still, slugs add no value at pistol distances, why shoot them?

I'll look for the chamfer again. Maybe I missed it. The view is restricted when assembled.

I had the GK1 apart several times when installing my custom shroud. But I hadn't removed the barrel and magazine. Probably was only two steps away from that. Next time, I will take a look at it again. I do want to measure both the mag and the barrel.

For me, since I cast my own, a slug is cheaper than a purchased pellet, so there is value for me, at all distances. They are cheaper, therefore a greater value. My slugs happen to punch a cleaner hole, almost like a wad cutter, definitely better than a dome. So easier to score. One down side is they maintain velocity better, which can be an issue for certain situations. A pellet, with inferior ballistics might be better, if you need it to run out of power sooner. It's something a responsible shooter has to do - evaluate their shooting environment to ensure safety.

For those that don't cast, slugs are currently priced at a premium. (Cool kiddy tax?). Pellets might be more cost effective than slugs, if you aren't making your own. Personally, I think prices have gone way up for pellets in the past five years. But one could say that is true for a lot of things.

Slugs that have a proper drive band do seem to work in the GK1. Mine do. Some slugs that don't have that feature appear to have issues, at least from the comments I hear on AGN. I suspect some of the issues may be due to improper sizing of the projectile to the bore. Maybe a narrow drive band is the best (lowest friction) solution to the GK1 slug problem, not sure. Maybe some clever folks can come up with a better way.

 

[Ezana4CE]

@WobblyHand Knurled slugs are another option.

 

[WobblyHand]

@WobblyHand Knurled slugs are another option.

Agreed. I was going to mention that, but my post started to get way too long. Couple of members here have had success knurling to increase the diameter of slugs. It opens up the number of slugs that will work, although there is labor involved. Kind of like casting, I guess!

 

[steve-l]

If you don't consider your time as valuable, your cost assessment is correct. If you enjoy casting lead, that's a different story. It's your time and your hobby do as you wish, but your case is not for most of us. Slugs cost twice as much as pellets.

 

[WobblyHand]

If you don't consider your time as valuable, your cost assessment is correct. If you enjoy casting lead, that's a different story. It's your time and your hobby do as you wish, but your case is not for most of us. Slugs cost twice as much as pellets.

My time is valuable, so I spend it in a way to that gives me some amount of pleasure. As for my time having actual cash value, hah, good luck convincing the tax man, they think it is worthless. I totally agree with your argument about commercial slugs, unless you need the terminal ballistics, slugs don't make too much sense cost wise.

But for me, the cast slugs are a better value, since I can't get paid for my time these days. I've got about 15 lbs of lead right now, so that's what? I figure that's over 3100 slugs that I can cast.

I enjoy making things, casting is just part of it. I enjoy designing stuff and making it, be it via machining, printing, or welding. Nothing gives me more satisfaction than using things I've made. So casting my own slugs and shooting them in an airgun I modified to my liking, yeah that gives me pleasure.

Using a Doppler chrony that I made from scratch, that gives me pleasure too. I designed the circuits, simulated and tested them, did the systems analysis and loss budget, selected a capable platform, wrote the signal processing code and stuffed it all in a printed box. Works well enough for my use case. Unfortunately, I was nearly complete, when the FX chrony came out, so my dreams of fielding a low cost rig died. Couldn't see a viable commercial path for me, with their head start. I know what it takes to get radar systems approved, and commercialized, I did it professionaly. Been to official test labs in the US and China for world wide type certification. No matter, I got a heck of a lot of pleasure figuring out the puzzle and doing it myself.

 

[MrP]

i think there is some concern about abrasion on the skirt of the pellet or the trailing edge of a slug, on the oem loading gate.
I prefer the swing gates myself, and in fact find myself sometimes picking up two slugs just right, and dropping them in there at once.

The OEM gate also lends itself better to seating tools, if you use one of those. I know Kelly provides a fill plug with a 2mm seating tool on the end of it...not sure how many people seat them tho.

I can see how that might be an issue especially with .22 cal. I have a tin of jsb .22 cal 18.?? grain i think and those skirts seem very thin / fragile.