Kral Jumbo project. Some observations.

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Vetmx

Vetmx

Member
Dec 4, 2017
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Pa, United States
A couple weeks ago I was at my sisters in Va for Pelletfest. My brother-in-law took to my FX. When questioned, he said he liked it for our longer range targets because of the accuracy, shot count and how it cocked. He is a ham fist, sometimes firing two pellets at a time out of my FX because he was gabbing. I decided to build him a gun and since I never owned one, I figured I would try a Kral. This Jumbo is going to be around 36-37” with a functioning shroud so there will be no need to hang a can on it and make it longer. I am waiting on the reg but in the meantime I built a 15.5” barrel for it. Here are some things I learned about this gun that other Kral owners probably need to know. When the power adjuster is set to max, it is actually over rotated. I didn’t like how the gun sounded when I was shooting it after the barrel build. I also found the bottle block transfer port was not lined up. If you remove the barrel and back screw, you can look down through and see if everything is lined up. I was able to line it up by just loosening the screws and tightening it up. The factory dimples were a little off. The last thing is the barrel transfer port. On the .22, if you make it any bigger, your pellets skirt starts to be exposed to the transfer port. So before you start drilling your barrel, load a pellet, take off your barrel, and have a look see to see how much room you have to work with. I would do this with any gun before you break out the drill. A skirt hanging in the TP is an accuracy killer. I am going to shoot for 18.1’s around 850 with this gun once I get the reg in. I can oval port the valve and the barrel but that stupid power adjuster is going to involve some thought. I like shooting it but can’t wait to get the reg in and get that hammer strike backed off. Unregulated guns really hammer the valve and I am not a fan. Here it is after Phase one. Shorter barrel and CF bottle. Don’t get me started about getting the aluminum bottle off. Good grief. I will revisit this topic as the project progresses.
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It does shoot very consistently without a reg but it will feel and sound much better when I am tapping that valve at 1,800psi and the gun isn’t all choked off to maintain consistency. Kral definitely figured things out for an out of the box unregulated gun. The side lever won’t be an issue when I get rid of the truck spring they use because of it being unregulated.
 
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Troy H makes a twin spring and hammer solution for these new gen Kral guns. There is some heavy cutting and drilling that needs to happen to the bolt, but it is worth it. The hammer spring adjustment will help you find the dynamic sweet spot for your pellet of choice. My own Kral loves the heavy Seneca pellets at 28.5g in . 22 with the Hades a close second.. It does not like some of the JSB line and none of the H&N.



Keep up the good work!
 
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What was the reason for shortening the barrel? I just picked up a jumbo in 25 and I will say I’m quite impressed.
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It’s going to be nothing other than a pellet gun so there is no need to have 22 inches of barrel to get the velocity I want. I plan to have this gun no more than 37” long and quiet. In its original form with a mod screwed on it was 45” long and kinda quiet. But it took making it 47” long to make it quiet with a longer mod. I’m not into the goose gun look. Even though it is called a Jumbo, I’m going to put it on a diet.
 
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Made some headway yesterday. Built a SSG, ported the whole gun, installed the reg and modified the stock to accept the SSG. Had the gun shooting 14.3’s at 930fps but didn’t like how the gun sounded. As I tightened the spring in the SSG, increasing free flight and lowering velocity, the gun sounded sweet at 913fps. I would like the gun to shoot cheap pellets so I may have to slow those 14.3’s down some more and lower the reg. Once I decide on a tune, I will do a shot count. For now, here are some pics of what I did. I will put the gun back together tomorrow after the finish dries where I modded the stock for the ssg.
 
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Put it together today and did some shooting. I get 114 shots above the regs set point. The whole gun is much more quiet than when it was unregulated. Feels and sounds like a quality PCP now. For the time being I’m going to stick with the 14.3gr pellets at 913fps. They are accurate and will work fine for the guns intended purpose, volume target shooting. Here is a pic of the finished quiet gun next to the shroud it came with. Even with the Huggett, it wasn’t as quiet as it is now. No more pinging and blubbery hammer bounce. Hope it holds up because it’s a pleasure to shoot.
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Would you mind helping out a newb. I am super happy with my Kral puncher jumbo but a few things I would like to tweak. After installing the moderator it’s nice and mellow but you get a ping when firing. I’m guessing it from the bottle as it sounds similar to when I flick the side of the bottle with my finger. I have read about how people solve that but can it be done in a bottle? The gun seams accurate enough so I don’t want to loose that. A regulator would be really nice to add but it looks like all regulators are external with none built into the bottle. I am a machinist by trade so I can make just about anything. I want to keep the velocity as we have large varmints to deal with. Just looking for alittke direction on options. Thanks. 
 
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When you install a regulator, the ping goes away. The reg screws onto the bottle so it moves the bottle forward like 2.5'. Its been a while since I shot a full power unregulated rifle. When I first shot this gun, I was like yuck, sounds like I am shooting a piece of junk. Its accuracy and consistency were good, but when you are used to shooting nice efficient guns, the Kral sounds rough. It makes so much unnecessary noise that it was hard to detect how much hammer bounce it had until I filmed the hammer through the slot in the side of the receiver. When the reg helped quiet the gun, the hammer bounce became extremely evident. You wont get rid of the ping unless you put a reg on the bottle. Right now when your hammer strikes that valve pin, air from the bottle is slamming the valve shut. When you install a reg, its basically is another valve inline with the bottle that stops that.
 
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