Jkhan Grandeur .357 tune for more power

[Rough Landings]

Is anyone doing a power tune on these Jkhan's?  I really like the fit, finish, ergonomics, and accuracy of these, but they are weak on power at just over 100fpe.  I would like to get this up to 150-200+ fpe and don't see why this wouldn't be doable as the Recluse is running in that range.  If I could get 6 shots max before a fill at that power range I would be happy.

[oneshot61]

From what I understand they share a lot with the evanix. I have the noblesse in .22 but have not opened it up yet. This link may help.  http://www.gatewaytoairguns.org/GTA/index.php?topic=58699.msg793090#msg793090

Someone with more skills than I could ever offer should chime in soon.

[rkr]

Grandeur does not use the same parts as RS2 so the tuning details from my thread do not apply fully. Grandeur seems to have separate transfer port so I don't know how big you can drill it, 6.75-7mm would be good if it's matched to valve tunnel area minus the valve shaft. Then tune the hammer weight and hammer spring to match, again I don't know what components are used and how they work so I can't tell you whether to increase or decrease the weight. A stiff hammer spring with negative preload is usually good for air usage and may provide enough power. SSG is another rather interesting alternative. Those double tube JKHans are rather rare guns so I doubt there are many tuners familiar with them. You could give Will Piatt a call, he's been tuning RS2s.

[Jagchaser]

Here are my numbers after a tune.  Heavier hammer, reduced return spring weight, ported the return spring cap.

81gr JSB 200 bar fill
863, 854, 849, 840, 833, 826, 815 fps

95gr Air Venturi  200 bar fill
802, 816, 815, 807, 805, 801, 789 fps

67gr Roundball
915, 924, 918, 906, 894, 885, 878 fps

You can take the pellet retainer spring out, so the slugs can be cycled.  You just have to be careful not to lose the pellets/slugs when you are loading.

[Jagchaser]

I am pretty pleased with how it shoots now.  Before it seemed like just a paper puncher

[Jagchaser]

It might do even better with a heavier hammer spring.

[rkr]

It might do even better with a heavier hammer spring.

It would do better with improved air flow. After that you might see the benefits of heavier hammer spring. As it is now the gun is strugling to get the air to the barrel.

[Jagchaser]

It might do even better with a heavier hammer spring.

It would do better with improved air flow. After that you might see the benefits of heavier hammer spring. As it is now the gun is strugling to get the air to the barrel.

Have you opened one of these up?  The main airways are all pretty big.  I ported the return spring cap to allow more flow there, but the rest of the openings are about as big as the inside of the return spring. Without taking a mic to it, a 1/4"? 

The one thing that stuck out was the tiny orifice connecting the two tanks.  Do you think opening up the hole between the two tanks will help?

[Jagchaser]

All the main airways are already 6mm.  I would have think they are big enough?  Maybe just too much distance for the air to travel?

[rkr]

All the main airways are already 6mm.  I would have think they are big enough?  Maybe just too much distance for the air to travel?

6mm is not enough, that's what stock RS2 uses. 6.75-7.0 mm would give you a curve with JSBs.

[Jagchaser]

All the main airways are already 6mm.  I would have think they are big enough?  Maybe just too much distance for the air to travel?

6mm is not enough, that's what stock RS2 uses. 6.75-7.0 mm would give you a curve with JSBs.

I will have to do some measuring and see if its got the meat for a drill.

[rkr]

All the main airways are already 6mm.  I would have think they are big enough?  Maybe just too much distance for the air to travel?

6mm is not enough, that's what stock RS2 uses. 6.75-7.0 mm would give you a curve with JSBs.

I will have to do some measuring and see if its got the meat for a drill.

Check the valve tunnel and valve stem diameters while you are at it. The area there should match the TP area or perhaps be 10% more. Also check for sharp edge at the valve housing where tunnels meet, rounding it out in my Blizzard netted me some 30 fps if not more.

[JimmyBobby]

Are these guns good for only 6 shots at full power?

[Jagchaser]

Are these guns good for only 6 shots at full power?

I have mine tuned for 6-7 full power shots.  I could take the heavy hammer out and tighten up the return spring and get it back to stock which is more like 25-30 good shots if I remember right.  Just depends on how much power you want.

[KRJoye]

Velocity and shot count can be dialed in with hammer spring adjustment screw on a stock .35 JKHan Grandeur. I have mine set up for 3 mags (21+ shots) with with an avg of 770fps(w/JSBs) for approx. 110 ft lbs. I'm not a big hunter I like target shooting and plinking at 30-50 yards. I added a 5/16" delrin spacer between the stock hammer spring and adjustment hat screw. The spacer provides more adjustment at a step higher in fps than stock setup while compressing the stock spring for more power. Accuracy is fantasic, spread over 21 shots is about 30fps. I'm content with where i'm at for now.
Jagchaser i totally respect what your trying to achieve good luck with the performance mods!