Huben .25 Slugs for GK1?

[primaz]

That makes sense because the cross section area of a .25 is about 30% more than that of a .22. The current "happy point" (flattest shot string) of the .22 GK1 shooting 22 gr pellets is about 870 FPS. 870:700 is about 1.24, roughly agreeing with the 30% increase of cross section area of the barrel. The power wheel setting is about 1.75 rev. CCW from the min position, also roughly agrees with @killraven4334 's setting. My shot string is from a 325 bar fill, shooting down to about 210 bars for one clip (19 shots).

The interesting part is that 870 FPS is also the "happy point" for light pellets like GTOs and HN FTTGs. The power wheel setting is about 0.75 rev. CCW from min for the lighter pellets. The shot count does increase with lighter pellets.

All of these observations are consistent with the theory that it takes a flow of about 400 cubic inch per second (870 FPS * 12 in/ft * 0.11 in^2 * 3.14) to have any significant effect on the closing valve actuating faster. It'll be interesting when the .177 version is available because this calculation puts the MV to above the speed of sound in order for a .177 to achieve the same flow rate. Huben can probably tune a few variables for the .177 version to have a flat shot string centered around 950 FPS.

I have also observed the first shot being slower, but not that much these days. If projectiles are wet-lubed, that can partially explain it because the lube may get viscous as it dries in the barrel. I dry lube my pellets using a PTFE spray where the solvent/carrier dries before I load the pellets.

Have you heard anyone reporting the accuracy of the .25 GTO lead free pellets and what is the ideal FPS to shoot those? Those pellets are cool but a bit pricey. I am still intrigued as some of reported that in the .22 caliber they felt that it was slightly more accurate with no issues on jamming; but I have not seen anyone providing feedback on results with the .25?

 

[sactargetshooter]

@primaz , I have no experience with the .25 version of GTO pellets. However, I can share what I know about the .22 ones.

The GTO pellets are lead-free. They are light and made of a hard alloy. In .22, these pellets fit the magazine well and do not jam. Turning down the power setting, these pellets also shoot out of my GK1 accurately, even at extreme slow MV. I have read other AGN posts that these pellets also shoot accurately at higher MVs (between 800 and 900 FPS).

They are pricey. But you can shop around and find better deals. I ordered a sleeve from Utah Airguns, and the package arrived with the pellets well packed and protected. Unlike JSB (especially the thin skirted RS) pellets, these hard alloy pellets can take a beating and not get bent!

 

[dflo]

Have you heard anyone reporting the accuracy of the .25 GTO lead free pellets and what is the ideal FPS to shoot those? Those pellets are cool but a bit pricey. I am still intrigued as some of reported that in the .22 caliber they felt that it was slightly more accurate with no issues on jamming; but I have not seen anyone providing feedback on results with the .25?

If you want lighter .25 pellets, try the 20grain from H&N. They are fairly inexpensive since less lead. I just bought some and going to give them a try.

 

[dflo]

my testing agrees with the low to mid 700's for the flattest power curve in the .25 V3 Gk1. I was looking to min mx the extreme spread with the highest possible fpe for 1 full magazine of 17 shots. My best results after testing nearly a thousand rounds across a dozen different slug weights, head sizes, and brands was the 41 grain zans at 734-750 fps, for 17 shots all above 50fpe. this shot string starts at 300bar and ends at 19bar. I should have taken notes on exactly how many turns it took to get there, but I started at two full turns up from min and adjusted 1/8 of turn after each magazine until the curve flattened. Also, I still occasionally get a slower first shot, (like 690 fps, before it jumps back up to 750, doesn't always happen but it drags the spread to 60 when it does) not sure if thats due to filling above where I normally do, might have been up to 310 bar or the valve sticking a bit after sitting when reloading and refilling. Will be doing more testing this week once I get more deliveries of the other slugs I ordered to test with as the accuracy of all the slugs ive tested outside of fx hybrids is pretty crap at this low speed. So while its speed and power are consistent, the group is 2 inches at 25 yards, which is not ideal.

Thanks! Good info to have. What size Zans are you using? .253 or .254 or something else?

 

[Airgun561]

If you want lighter .25 pellets, try the 20grain from H&N. They are fairly inexpensive since less lead. I just bought some and going to give them a try.

Speaking of .25 pellets..anyone try the H&N hornets?looks like they might have the flared skirt and reg .250 body the JSB’s have that work so well.

 

[Asher]

Been liking the ones I've been making. Unfortunately the .2537s I had a die made in just weren't as accurate for me. It likes the .254s better, as everyone else says.

I can make hollow points or nound noses. It likes both about the same which is to say very well. I basically make them to fill the magazine, just a fraction of a mm shorter so the seating is very satisfying. The round noses are a bit over 46 grain and the hollows end up right at 50. Dont have many group pics but here is a pretty good one shot at 15 yards if I recall... using the iron sights and a bag rest. At the distance I shot at it, the green circle looked to be about as big as the sight dot. No pics of groups at further distance but I seem to be able to hit cans off hand pretty consistently out to 50 yards and with a few tries at 75.

 

[Emjay4248]

I can find out from a few friends se if they are using slugs. Your using the .254 size link the k1 likes?

Spoke to Gregor the designer of the gun and he said the ideal size is .252 which of course is not available but .253 is ok too. The reason is that the barrel is .250 Magazine is .252 to accommodate the skirts on pellets. Some people use AVS 254 but the only reason they work is made out of pure lead and soft, but they must leave a lot of residue and trim the barrel. I am going to try zan .253 I have been told they work very well. They are out of stock at the moment at The Pellet Shop, which is where I get my stuff so I will wait another week till I get them.

 

[Nomadic Pirate 66]

Yup I call it good and sticking to JSB MK II and EunJin 43gr,....no need for me to chase bullets when those 2 perform exceptionally.

 

[Emjay4248]

Yup I call it good and sticking to JSB MK II and EunJin 43gr,....no need for me to chase bullets when those 2 perform exceptionally.

Without knowing if you just help me out, I just ordered some of the EUNJIN pellets and that solves my problem. All I wanted was something heavier than the JSP mark twos information eliminates my needs for slugs thank you.

 

[Nomadic Pirate 66]

Without knowing if you just help me out, I just ordered some of the EUNJIN pellets and that solves my problem. All I wanted was something heavier than the JSP mark twos information eliminates my needs for slugs thank you.

Remember if you ordered the EunJin 43gr you will need to clip the tip a bit so they fit

 

[Emjay4248]

Remember if you ordered the EunJin 43gr you will need to clip the tip a bit so they fit

Didn’t know. Not a problem thanks again

 

[Emjay4248]

Ive been using Zan .254 38 grain slugs. They seat well (albeit a little tight) and they don't rattle around in the mag. I will look into other options later on, but getting my hands on other .254 slugs requires importing them from other countries. The assortment is painfully small where I live. Preferably I'd like some 40 grainers.

He makes a 253 for the gk1 in 33 and 38 grain

 

[miksatx]

Apolo Puncher pellets look interesting comes in .25. None in stock yet though.

HatsanUSAApolo Puncher

.25 caliber; 37 gr; 200 pcs/tin Heavy hunting pellet; Smooth with hollow point Extraordinarily accurate for medium & long distances High penetration depth and controlled deformation Achieves sm…

hatsanairgunsusa.com

 

[Emjay4248]

Apolo Puncher pellets look interesting comes in .25. None in stock yet though.

HatsanUSAApolo Puncher

.25 caliber; 37 gr; 200 pcs/tin Heavy hunting pellet; Smooth with hollow point Extraordinarily accurate for medium & long distances High penetration depth and controlled deformation Achieves sm…

hatsanairgunsusa.com

They are 6.35mm =250=too small

 

[miksatx]

And? I shoot jsb kings .25 in my GK1 that are .250.

 

[Emjay4248]

This does not have a flared skirt like a pellet. They will be loose. You need at least .252 for it to stay in place. I’m using zan.253. A little tight but they shoot well. Good luck with those

 

[miksatx]

This does not have a flared skirt like a pellet. They will be loose. You need at least .252 for it to stay in place. I’m using zan.253. A little tight but they shoot well. Good luck with thoses

Well if they don’t work out I can use them in other guns lol. I’ve bought Apolo pellets before they never look as good as the picture.

 

[Emjay4248]

Yeah that seems to be with all of hatsan’s stuff