Hatsan Jet I/II Discussion

[JPSAXNC]

@ James, If you are using a stiffer hammer spring to get more power. A little more power can be gained by turning down the bolt probe diameter from .120 to .080. The bigger probe diameter blocks the air flow into the barrel.

[naptemp]

@ James, If you are using a stiffer hammer spring to get more power. A little more power can be gained by turning down the bolt probe diameter from .120 to .080. The bigger probe diameter blocks the air flow into the barrel.

To detune a .177 Jet 2 and get a flatter shot string, I assume I would need:
-weaker hammer spring
-stronger valve spring

Anything else?

[JPSAXNC]

Hi John, I would try the weaker hammer spring first. The stronger valve spring well help shot to shot consistency, and shot count.

[naptemp]

Hi John, I would try the weaker hammer spring first. The stronger valve spring well help shot to shot consistency, and shot count.

Thank you James for your help.

My goal is a long flat short string, power is not very important, just enough for my plinking up to 20 yards.

So, the stronger valve spring is the first to try?
For a 177 Jet what stronger valve spring do you recommend?

[avator]

I plan on checking function first. Next will be accuracy with some assorted pellets. And finally some strings over the chrono. Then I can determine what, if any changes it would benefit from. Anything I do to it will be reversible.

[JPSAXNC]

@ John, You probably know this, but I'll mention it. Make only one change at a time or you won't know what is effecting what. I would (start with the lighter hammer spring). A spring the same length as the OEM spring would be good, that way you will still have a free flight hammer.

[naptemp]

I will check for function (accuracy, power, leaks, etc) first.
If it is not accurate enough or the velocity is way too low or leaking I will send it back.

Assuming that all of the above are good.

I will go with a weaker hammer spring next.
I will use a different hammer spring (not the stock one) which I will cut as short as needed while shooting over the chrony.

I will ask more questions later

[avator]

I will check for function (accuracy, power, leaks, etc) first.
If it is not accurate enough or the velocity is way too low or leaking I will send it back.

Assuming that all of the above are good.

I will go with a weaker hammer spring next.
I will use a different hammer spring (not the stock one) which I will cut as short as needed while shooting over the chrony.

I will ask more questions later

Exactly..
I don't know your experience so I will offer this..
Shorten the hammer spring in small steps. It don't take much to make a significant difference.
Along with hammer and valve spring, reducing or enlarging the ID of the transfer port also can make changes in performance.
I personally have to be mindful when I take guns apart and put together back together because I tend to be a bit ham fisted and impatient. For me that has resulted in putting things on hold until new parts came in that I wrecked.
I once converted an SPA CP1/CP2 to PCP with PP800 parts. With the help of a couple more experienced members I set out to tune it for the best bell curve for accuracy and shot count. It's a length thread because I tend to "wander" in my threads but I'll post a link to where we got into the meat of the tuning.
Maybe it will help and maybe not.
https://www.gatewaytoairguns.org/GTA/index.php?topic=182687.msg156082734#msg156082734

[avator]

LOL... that thread contained a picture of the cantilever riser and scope I'll be using on the Jet 2.
 

[EdinGa]

LOL... that thread contained a picture of the cantilever riser and scope I'll be using on the Jet 2.

I don't remember seeing your setup before, but I'm pretty sure that's the same scope and riser I'm running on my wife's Chaser carbine. Just because I don't remember doesn't mean I didn't steal the idea from you when I built it though. 

[avator]

I remember buying 2 of those risers for the Crosman 362 rifles but I would have to dig a little deeper to find where I got them.
Not a good pic of it but I'll post better pics in the thread I plan to post on the Jet 2 when I get it in my hands. Hopefully that will be tomorrow. I'll post a link here to that thread. My personal goal will be to follow the same path in setting the Jet 2 as I did with the PP800 build.

[Back_Roads]

 Spent some time thinking and tinking with the .25 Jet1. I invented the "Trigger Tube", as a quick way to test my theory that a trigger shoe would be nice, and it is.


 Hacked a multi purpose clamp to hold the bottle steady, I may shape it to the contours, but flipping one side opposite did the trick for now.



 Been having issues with silencers not giving me accuracy, I went back to the drawing board on an old attempt from the past. This was a custom shifter knob, now it removes bark
 Introducing the Jet1 Back_Roads Space Cowboy Edition 

[avator]

Man.. that thing looks front heavy as heck. I bet it's fun to shoot though.

[Back_Roads]

Man.. that thing looks front heavy as heck. I bet it's fun to shoot though.

Actually the weight helps it settle in, shoots best off of a mono, or bipod, does not bench rest well not too shabby off hand now either, I get less wiggle with the weight.

[EdinGa]

I've got a Nitecore p30 clamped to mine and it weighs 5.8 pounds. I haven't checked the balance point, but it isn't tiresome to shoot.

[EdinGa]

Man.. that thing looks front heavy as heck. I bet it's fun to shoot though.

Actually the weight helps it settle in, shoots best off of a mono, or bipod, does not bench rest well not too shabby off hand now either, I get less wiggle with the weight.

I think I have a clamp like that. I'll look around and give it a try if I can find it. I'm using a steel cable tie right now.

[avator]

I've got a Nitecore p30 clamped to mine and it weighs 5.8 pounds. I haven't checked the balance point, but it isn't tiresome to shoot.

LOL.... looks like something that may have recently been declassified.

[EdinGa]

I've got a Nitecore p30 clamped to mine and it weighs 5.8 pounds. I haven't checked the balance point, but it isn't tiresome to shoot.

LOL.... looks like something that may have recently been declassified.

I can definitely see that. I might break it down if I ever travel with it. 

[avator]

I've got a Nitecore p30 clamped to mine and it weighs 5.8 pounds. I haven't checked the balance point, but it isn't tiresome to shoot.

LOL.... looks like something that may have recently been declassified.

I can definitely see that. I might break it down if I ever travel with it. 

LOL... yeah, probably not a "carry on" item.

[Back_Roads]

I've got a Nitecore p30 clamped to mine and it weighs 5.8 pounds. I haven't checked the balance point, but it isn't tiresome to shoot.

LOL.... looks like something that may have recently been declassified.

I can definitely see that. I might break it down if I ever travel with it. 

 Maybe something like this with radiation warning stickers on it