How’d the thread go from discussing the GK1 to the Huben K1? Are the last few posts accidentally calling the GK1 a K1 or are you folks actually discussing the rifle instead of the pistol? It’s a bit confusing to follow.
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Huben Any issues or problems with Huben gk1 please share your experience
- Thread starter windowtintz
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Who has gotten acceptable results shooting JSB KO slugs from a GK1?I'm not sure, but maybe the JSB Knockout MkII qualify as "girlie" with their mini-skirt?
Matthias
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What you folks are referring to are Striations, not rifling. They are caused by lead smearing through friction. Those bores in the mag are smooth. The mags are the same in both the GK1 and K1. Although I have only GK1s in .25, I can assure you the mag bores are exactly .250 in diameter checked with a precision set of pin gauges, which I own. To prove my point, remove your mags with these striations and clean their bores with Hoppes number 9 and a bronze bore brush and see for yourself.
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For those of you that are not aware or knowledgeable about revolver technology. Cartridge retention in the cylinder is achieved by the flange base of the cartridge case, just as the pellet skirt is used in the Huben guns. With the exception of the Webley 38 and 455 revolvers, all other revolvers use a single forcing cone design at the beginning of the barrel this swages the bullet into the barrel's rifling, which is significantly smaller than the OD of the bullet. The Webley design actually does this twice, once in the cylinder and again in the forcing cone. The purpose of the forcing cone is to compensate when the cylinder and barrel is slightly out of perfect index. This is a non-issue with a powder burner because you have around 10 to 30 thousand pounds of pressure pushing the bullet. This luxury does not exist in an air gun. The driving pressure is much less. In that light, bore resistance must also be less, hence the use of the Diabolo skirt for both retention in the magazine and the lower bore resistance in the barrel. The Webley bullet is a hollow base design made from almost pure soft lead very similar to a Diabolo pellet. Most slugs, on the other hand, have parallel sides because they are made by swaging a piece of pure lead wire through a sizing die. This design creates a very high level of drag in the barrel, far more than can be useful in an air gun. If you look closely at the JSB Knockout slugs and measure with a micrometer, you will note that the slug sides have a slight taper and are NOT parallel. This limits the bore resistance in an air gun, but the OD must still be larger than the magazine's bore as resistance in the bore is the ONLY way it can be retained, but it still offers a very high level of bore resistance in relation to a Diabolo pellet. A slug's advantage is only BC and I suggest at pistol distances, that better BC offers no advantages. Some here have stated that slugs are heavier therefore carry higher energy, that is true but at slower velocities as well, which makes aiming considerations to compensate for drop also more challenging. You can now add to that the much greater cost per round with slugs and the criticality of slug diameter to that equation. Your call, it's your gun.
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Peering into my GK1 mag, with a light shows there are 6 grooves. They are pretty thin, but I can see they are spaced evenly. Can't say if that is true for all of the holes, but it's true for a sample of one. They look just like @sb327 's photo.
My slugs have a narrow drive band. That's the primary engagement into the rifling. The nose rides on the lands. There is no skirt. As you can see, there's a small boat tail and a hollow point. My NOE 217-30-FN-BJ5 RG2 Cav BT slugs are a snug fit in the magazine. They are cast using 99.9% pure lead. This is a drawing of the slug. A few posts earlier were of some sorted slugs on my desk.
Not saying that I won't have problems in the future, but, right now, I have had no issues firing 500 of these 28.4 grain slugs at 777 fps. No evidence of them moving in the magazine, no slivers, no jams. At the moment, unless the magazine prematurely wears, I can't see a reason why they'd start slipping. I think the assertion that no slugs work in the GK1 is not grounded in fact. Mine do, and it appears other members can shoot slugs too.
It could be that process variations in both the GK1 and the ammo that is being used can cause issues. Since we can't find an alternative for the GK1, it might be a good idea to check the ammo. So who checks their slugs that they actually measure what is claimed? And with a micrometer? Because most calipers aren't that accurate. They require the operator to use them a very specific and uniform way. Most people don't use them properly, myself included at times. A micrometer is far more accurate. If slugs are like most commercial pellets, they vary a lot. And that might matter a whole bunch for a GK1. Small slugs will slip. Properly sized ones won't.
My slugs have a narrow drive band. That's the primary engagement into the rifling. The nose rides on the lands. There is no skirt. As you can see, there's a small boat tail and a hollow point. My NOE 217-30-FN-BJ5 RG2 Cav BT slugs are a snug fit in the magazine. They are cast using 99.9% pure lead. This is a drawing of the slug. A few posts earlier were of some sorted slugs on my desk.
Not saying that I won't have problems in the future, but, right now, I have had no issues firing 500 of these 28.4 grain slugs at 777 fps. No evidence of them moving in the magazine, no slivers, no jams. At the moment, unless the magazine prematurely wears, I can't see a reason why they'd start slipping. I think the assertion that no slugs work in the GK1 is not grounded in fact. Mine do, and it appears other members can shoot slugs too.
It could be that process variations in both the GK1 and the ammo that is being used can cause issues. Since we can't find an alternative for the GK1, it might be a good idea to check the ammo. So who checks their slugs that they actually measure what is claimed? And with a micrometer? Because most calipers aren't that accurate. They require the operator to use them a very specific and uniform way. Most people don't use them properly, myself included at times. A micrometer is far more accurate. If slugs are like most commercial pellets, they vary a lot. And that might matter a whole bunch for a GK1. Small slugs will slip. Properly sized ones won't.
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My apologies, both my V1 and my V3 have those grooves. I missed them. I did however recheck the bore size in both my 25 cal. V1 and V3 magazines. The sizes are the same .250 go .251 very tight almost no go.. My barrel land diameter is .247 go .248 no go. These sizes are the same as I reported earlier in other threads here on this forum. Those grooves are NOT rifling, just grooves.
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You are correct, they are not rifling. I said they are rifling LIKE lands in one of my previous posts on the subject.
I have posted in other threads on the forum a way of ‘knurling’ common slugs that works perfectly for the huben mags and transition to barrel (forcing cone). And are easy to load.
Dave
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I've had adjusted mine to shoot .25 Hades at 40 joules. Fired a bunch this weekend when suddenly the gun sounded different and I felt a power loss. Now it's only putting out 10 joules no matter what. I've screwed the power adjuster all the way out and no change. The valve must be stuck. Anyone had that issue before?
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User Error, this gun is a flawless unit. (/sarcasm).
What was your fill pressure on this unit at the mere 30 fpe you were shooting it?
-Matt
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Sorry this happened but glad you found the issue quickly and shared it here. That should be an easy fix with a new closing valve.
Did both springs appear ok?
Dave
Did both springs appear ok?
Dave
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The springs are good. Maybe a rookie mistake. Here's my thought of why this happened. When you remove the trigger guard make sure that you only put it back on when the system is depressurized or screw the adjustment screw all the way out to prevent any force on the on the closing valve. Perhaps that lead to damaging/weakening the valve. It's an quite expensive part. Costs 30 Euros
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Interesting part. Doesn't seem that complicated, but perhaps I'm over simplifying it, and shouldn't. Does something go through the bore? Ah, part 21, the close valve spring stem goes in part way. Looks like a simple lathe project, and a small sized one at that. If I have to deal with that, maybe I'd make one out of aluminum. Seems like that plastic piece is marginal for it's load - even if by a rookie.
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Removing the trigger guard should have no effect on the closing valve. I’m sure you are aware but it is contained via the adjustment stem housing (brass) and that part doesn’t get disturbed by just removing the trigger guard.
What pressure were you running in the reservoir?
Dave
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