Here is the chart of sweet spot I assume..
Also for reminder JSB King Exact 25.5 Grain.
Mike
Also for reminder JSB King Exact 25.5 Grain.
Mike
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Kral Arms Tuning Unregulated PCP - Running out of Hammer Spring Adjustment
- Thread starter CanMike
- Start date
Do you think this is happening because we are driving the gun harder than it was intended? If we left our guns alone and dialed them in only with what Kral provided, porting/spring, would we get better results? Even if it was at a velocity or fill range that we didn’t like? I was just thinking some of what we talked about privately could be self induced because of what we want out of the gun.
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Dang Mike, I think I could live with that. Might be time for some accuracy testing. I would shoot a couple groups at the beginning of the sweet spot and a couple towards the end of it and compare them.
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Keep the chart you posted in post #21. You’ll need that if you ever decide to put a reg in the gun. It tells us some things about where the gun is and wants currently without any modifications. But let’s not go there right now. You might have a gun that’s going to suit your needs without going down a reinventing the gun path.
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That tune with that weight pellet is about ideal ... IMO
If wanting / wishing for greater speed you will need to find a lighter pellet.
* I would HIGHLY recommend trying the JTS 21.6 grain semi-dome. With a tad less weight it will be faster and perhaps make equal or greater FPE numbers ? ( They are in my testing more accurate than JSB 25.4's
)
If wanting / wishing for greater speed you will need to find a lighter pellet.
* I would HIGHLY recommend trying the JTS 21.6 grain semi-dome. With a tad less weight it will be faster and perhaps make equal or greater FPE numbers ? ( They are in my testing more accurate than JSB 25.4's
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I agree. Especially with the valve dwell vs barrel length on these setups. I just removed those smaller hammer weights you made for me and my accuracy went up with the 11" barrel and stock bottle on the np03/jumbo I built.
Oddly, it was dead nuts on when I had the dazzle drop block and heavy 350cc aluminum bottle. I changed out the drop block to the jumbo setup to fit back in the jumbo stock, and my accuracy started doing the shift horizontal when pressure drops. Has to be the porting and valve poppet design being different in the dazzle valve that was the only change. I removed those weights and now it's stacking again.
Stranger things I suppose.
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Seemed pretty accurate. It likes these pellets. So I guess I should leave as is. 800 was kinda the goal.
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I’m a little rusty when it comes to unregulated guns. I think it’s been two years since I “reinvented“ my Kral Empire XS. But peace of mind came when Motorhead posted and said leave it be, it’s good. That’s the beauty of these forums. And yes, if you are going to be a backyard Bob with a .25, 800fps is plenty and still better than a .22 at 880fps. Hope you enjoy it.
Heres another thing I do with my unregulated guns. Mainly because they don’t get shot often. Not because they are inferior, it’s because they are superior to a regulated gun. They can sit in my garage or down at the shop for months. When someone grabs the gun, it will be spot on with the first shot. But the problem is I forget my fill and refill numbers. So I do this.
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I’ll see if I can source those but the JSB are very accurate. I also have so. h/N trophy which are 20 grain and those fly 50-70 FPS more. Those are less accurate.That tune with that weight pellet is about ideal ... IMO
If wanting / wishing for greater speed you will need to find a lighter pellet.
* I would HIGHLY recommend trying the JTS 21.6 grain semi-dome. With a tad less weight it will be faster and perhaps make equal or greater FPE numbers ? ( They are in my testing more accurate than JSB 25.4's
If I am also understanding the mechanics if I wanted to tune for more speed and leave the hammer as is I would need to open the transfer port from the 3.6mm to for example 4mm.
And if I wanted same speed but with the larger transfer porting I would back the hammer spring down.
Am I understanding things correctly.
Thanks for all the help. I love understanding how things work equally to having fun with the rifle.
Mike
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That’s a great idea marking the gauge.
I reset my compressor to 220PSI fill for now. May drop to 210 on next fill.
Mike
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Thanks. I think I’ll forgo the regulator. But if I understand correctly. Asked on chart I would set regulator to about 140/150?
Mike
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I’ll fix this quickly for ya…
Benjamin Cayden and Reximex Daystar are the same action - use the same hammer spring.
Crosman uses a 4.25” spring in the .25 Cayden. Your spring is only 3.75.
Get the Crosman spring for $3.50 and try it - before you do anything else. You can always trim it to 4 inches or less if its too strong at 4.25 inches.
Edit: call Crosman service - which is Velocity Outdoors. The picture shows the part# and actually length of .25 caliber spring.
-Ed
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In a UN-regulated PCP, as ports increase in size the bell curve profile gets worse as in ... ES over a given fill pressure range will increase.
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No, you would immediately port the gun because shooting a pellet out of almost a 600mm barrel at 810fps with a reg setting of 140b is just plain silly. The gun would be very unhappy. But at least you know where the gun is at stock. After the gun is ported to whatever it will allow, you might be at let’s say 850fps at 130b. But something still isn’t right. The gun seems loud or blubbery. That’s because at this low of pressure, your hammer is too heavy and definitely bouncing. So now you have to deal with that in several ways. You also have to be concerned with plenum volume. If your gun is a tube gun, plenum size for a .25 can take up valuable air capacity space. If you have a bottle gun then proper plenum volume with a reg is going to move that bottle way forward.
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What Motorhead said in post #33 is where guys open a can of worms. The second I opened up my Empire XS for more velocity, it sent me down another path of trying to get my efficiency back. It was fun at first but it started to wear on me because I’m not a “good enough“ kinda guy. The safest way to pick up a little speed with a Kral is with the poppet. Decrease the diameter of it and let your stock porting do its self regulating duty. But you have to know what you’re doing. Is going in there and messing with the poppet worth it by itself? No. But coupled with other mods as a package, yes. But then you have to play the bell curve game and ES game.
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I wish I could armchair some for ya but I haven't the slightest clue about this airguns in and outs. I can only +1 @EPG 's suggestion as its quite sound from reply #32.
But unregulated guns CAN be tuned for more, or less power, one must understand that you are going to increase, or decrease shot count when doing so, its the nature of the unregulated beasts.
Definitely wouldn't hurt looking into a peek poppet with minimally needed diameter for a good seal, (.02"-.03" seat margin).
But for keeping it super simple, Reply #32 all day for $3.50 you cannot go wrong, and its reversible.
-Matt
But unregulated guns CAN be tuned for more, or less power, one must understand that you are going to increase, or decrease shot count when doing so, its the nature of the unregulated beasts.
Definitely wouldn't hurt looking into a peek poppet with minimally needed diameter for a good seal, (.02"-.03" seat margin).
But for keeping it super simple, Reply #32 all day for $3.50 you cannot go wrong, and its reversible.
-Matt
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Okay so port size staying put at where it is. I’m surprised how many shots I got. It’s only a 260cc tube. I’m going to try the longer hammer spring. It’s funny some versions of this action are over sprung and some under sprung I guess. Weird.
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