She has finally landed, Initial thoughts on the King (Kral)
I have been waiting to get my hands on the Kral from the time I heard about it from SHOT. Finally, a bullpup PCP at Marauder prices!
My first thoughts on the Kral Puncher Breaker Silent right from the box is how top heavy it feels holding it from the pistol grip but once your shoulder it, it balances out well. This is my first bullpup so the ergos will take a little getting accustomed to. Things I really like and was surprised how smooth the side cocking lever and trigger is. The lever being under some spring tension in the closed position, seems to aid in locking the lever back while engaging the sear. No grit or grinding whatsoever through its whole travel. The trigger out of the box is quite good! The first stage is a tad heavy but short as you feel resistance as you make contact with the second stage, which is very crisp, no creep and no noticeable over travel. The trigger is fully adjustable. The plastic stock feels like a real stock and not some cheap toy.
The couple things I am not impressed with is the provided rail which fastens underneath the handguard, is made of a flimsy plastic with a deep counterbored hole for the cap screw makes for a poor mounting system. No matter how tightly you turn the screw, the rail won’t stay in place. This should have been made of aluminum with extrusions to keep the machining cost down which would eliminate the flexing. The last thing is the shroud. It would seem the design is more form over function and will require some work before the Kral can be enjoyed in the backyard. I will being machining 1/2-20 adapters and air strippers for it.
Overall, I am impressed with the build quality, especially for its price point. The machining on the exterior is smooth without any tool marks (except for the safety level pocket). It handles well in my hands as I shoulder it and feels natural when I am acquiring the sight picture in my scope. I hope she shoots as good as she looks. I am curious how well an in-house barrel with preform. I will clean and lap the barrel and polish the crown before I run any pellets through. If the barrel is a lemon, I will machine a LW for it.
All Replies
Thanks for all the great theory and trigger parts information!!! I’ve never really spent much time thinking about how PCP airguns work, but I’ll be learning more as I start tinkering with these again.
Man, are those trigger parts ugly :suprisedn: I guess I see where the cost savings comes from, and I’d bet that explains the difference that’s being reported in the feel of the triggers. It’s probably just luck of the draw whether you get parts that are better or worse than others. After seeing that, I might have to take mine apart and clean it up.
Cheers,
Rusty
Kral’s trigger group is a very simple mechanism. There are three main components. The sear bar that holds the hammer in the cocked potion. The the middle piece I am calling an actuator that moves the sear and the “trigger” that moves the actuator where one would be if it were the rifle version. For the bullpup as you know, is separated and has the trigger forward of the breech which is connected by a trigger bar. For the trigger, I am focusing on the hammer, the sear bar and the actuator as represented below.
All the matting surfaces had rough, uneven surfaces which explains the grittiness I was getting. They literally hand grind these parts straight from the mold. You’d think they would employ smart fixturing and use CNC for this task…Even the sides of the trigger group are an uneven mess. (I’d hate to be the guy that has to hand grind by the thousands each day small little parts. I digress.)
Here is the before.
To improve the trigger, the first step I took was chucked the hammer in the lathe to cut a smooth lip on the edge fallowed by 400 grit emery cloth and polish (Hammer shown here, finished). Next, I coated the engagement surfaces (sear and actuator) with machinist layout fluid to see the high and low spots and keep track of material removal. I am not trying to take a lot off. Just enough to flatten the surfaces without changing the angle of the geometry. I proceeded with my gunsmithing medium and fine silica carbide stones.
After carefully stoning the surfaces while applying light pressure and keeping the faces flat against the stone, these are the results I got. The faces are now flat and much more even! The trigger pull now very distinct between the first and second stage while being buttery smooth with the aid of a little molly grease before reassembling :biggrinn:.
First of all thanks to you two for sharing all this stuff.
Concerning the data, it all makes perfect sense.
Lee said he had the hammer preload turned out. The hammer hits less hard and therefore opens the valve a little less in the brginning. While shooting, the pressure in the cylinder decreases and therefore putting less closing force on the valve, the hammer manages to open it a little wider / longer, the speed / power increases until the point where pressure drops and pellet speed / power start to decrease again, even though pressure further decreases and valve can be hit open longer. The valve return spring comes into effect as well.
We have a bell curve – quite flat in Lee’s case.
Rusty’s rifle is set to a higher power through harder hammer impact on the valve, opening it wider / longer from the beginning. After a certain number of shots, the pressure decreases, the power with it, same as with Lee’s rifle, but earlier. We find this often on Korean guns as from what I could read and experience. Indeed, we also have a bell curve here, just with a higher peak and moved to the left, starting directly on the high part.
I think that Lee is very close to a very usable and stable bell curve, the peak is a tad too far right in my eyes. It could be moved to the left by slightly increasing hammer spring preload, just a tad higher, starting with a bit higher speed / power.
It is indeed amazing to see this kind of curve on an unregulated gun, especially of this price point. Might really be a good pick.
Anyway thanks to you two for the detailed reports, I really enjoy reading them, keep ’em coming.
Your feedback is much appreciated. Thank you for taking the time to write a detailed response. I enjoy learning from others and sharing what I have done. I currently have my gun disassembled to do some trigger work and some mild porting on the valve transfer port. The other upgrade I am working on is a spring dampener. The action noise is louder than the report in my gun.
Hi Lee, hi Rusty,
First of all thanks to you two for sharing all this stuff.
Concerning the data, it all makes perfect sense.
Lee said he had the hammer preload turned out. The hammer hits less hard and therefore opens the valve a little less in the brginning. While shooting, the pressure in the cylinder decreases and therefore putting less closing force on the valve, the hammer manages to open it a little wider / longer, the speed / power increases until the point where pressure drops and pellet speed / power start to decrease again, even though pressure further decreases and valve can be hit open longer. The valve return spring comes into effect as well.
We have a bell curve – quite flat in Lee’s case.
Rusty’s rifle is set to a higher power through harder hammer impact on the valve, opening it wider / longer from the beginning. After a certain number of shots, the pressure decreases, the power with it, same as with Lee’s rifle, but earlier. We find this often on Korean guns as from what I could read and experience. Indeed, we also have a bell curve here, just with a higher peak and moved to the left, starting directly on the high part.
I think that Lee is very close to a very usable and stable bell curve, the peak is a tad too far right in my eyes. It could be moved to the left by slightly increasing hammer spring preload, just a tad higher, starting with a bit higher speed / power.
It is indeed amazing to see this kind of curve on an unregulated gun, especially of this price point. Might really be a good pick.
Anyway thanks to you two for the detailed reports, I really enjoy reading them, keep ’em coming.
BTW: What’s your preferred graphing program?
I have to believe the adjustments are the difference in the curve. Once we see a few more people posting shot strings, I guess we’ll know what’s more normal. I’m going to resist messing with mine, since it’s just something to play with until the Impact eventually arrives. I’m actually pretty happy with the super flat 30 shot string, and higher power.
I use Excel, but I’m just barely capable of making graphs. I don’t know how to do 1/10th of what the program will do.
Rusty
Thanks. It will be interesting to see the numbers as more and more Krals come online how consistent the results are. I hope they don’t fallow Hatsan’s example of over charging.
BTW: What’s your preferred graphing program?
I have to believe the adjustments are the difference in the curve. Once we see a few more people posting shot strings, I guess we’ll know what’s more normal. I’m going to resist messing with mine, since it’s just something to play with until the Impact eventually arrives. I’m actually pretty happy with the super flat 30 shot string, and higher power.
I use Excel, but I’m just barely capable of making graphs. I don’t know how to do 1/10th of what the program will do.
Rusty
The curve seems quite different between your string and mine, and I have to believe that there’s just going to be some variation in the way individual guns are tuned. Mine seems really flat over the first 30 shots, then it falls off steadily. Yours seems to be less flat at any given point, but spreads out the usable power over double the number of shots. Pretty interesting.
My 14.3 and 18.1 curves seem consistently shaped, with mainly a loss of velocity for the heavier pellets. I also note that for the first few magazines, my 18.1 gr results are pretty amazing for an unregulated gun. I hope the Impact can do that well (if it ever gets here).
Cheers,
Rusty
I do have the hammer preload all the way out on mine with the power wheel in the max position. Judging by the graph, I think our strings would be just able perfectly parallel if we started at 170 bar and shot down to 120. That seems to be the sweet spot.
BTW: What’s your preferred graphing program?
I couldn’t resist making this more scientific by using the same pellets you were shooting. I just shot a string and added my JSB 18.1 results to the graph.
The curve seems quite different between your string and mine, and I have to believe that there’s just going to be some variation in the way individual guns are tuned. Mine seems really flat over the first 30 shots, then it falls off steadily. Yours seems to be less flat at any given point, but spreads out the usable power over double the number of shots. Pretty interesting.
My 14.3 and 18.1 curves seem consistently shaped, with mainly a loss of velocity for the heavier pellets. I also note that for the first few magazines, my 18.1 gr results are pretty amazing for an unregulated gun. I hope the Impact can do that well (if it ever gets here).
Cheers,
Rusty
Attachments:
Cheers,
Rusty
Rusty, thank you for graphing the string! I need to get excel…
Equal and opposite reactions, I think the heavier pellet is more efficient with air because it closes the valve faster. I am quite happy to see a pretty flat, consistent string.
Interesting. I did a shot string on my .22 with 14.3gr pellets and the curve looks quite different. This is the first time I’ve ever done this with pellets, so I’m not sure if this is to be expected when changing weights, or if it just shows differences in the way the rifles are set up. Obviously I would expect lower velocities for the heavier pellets, but I would have guessed the shape of the curve would be similar.
Cheers,
Rusty
Attachments:
Now for the moment you have all been waiting for :biggrinn:
I started at a 200 bar fill and ended at 100. It stared leveling off at the 170 bar mark and dropped of at 100. Not bad at all for unregulated. I’m loving the shot count. The hammer spring is out all the way.
Created: 03-05-2017 05:38:45 PM
Description: Kral JSB 18.1
Notes 1:
Notes 2:
Distance to Chrono (FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight (gr): 18.130
Altitude (FT): 0.0
Temp: 52 °F
BP: 30.06 inHG
Shots
# FPS FT-LBS PF
76 766 23.62 13.89
75 768 23.75 13.92
74 771 23.93 13.98
73 775 24.18 14.05
72 776 24.25 14.07
71 780 24.50 14.14
70 784 24.75 14.21
69 792 25.26 14.36
68 787 24.94 14.27
67 790 25.13 14.32
66 789 25.06 14.30
65 792 25.26 14.36
64 789 25.06 14.30
63 792 25.26 14.36
62 794 25.38 14.40
61 798 25.64 14.47
60 799 25.70 14.49
59 804 26.03 14.58
58 800 25.77 14.50
57 ERROR 3
56 ERROR 2
55 802 25.90 14.54
54 799 25.70 14.49
53 801 25.83 14.52
52 799 25.70 14.49
51 799 25.70 14.49
50 798 25.64 14.47
49 798 25.64 14.47
48 796 25.51 14.43
47 793 25.32 14.38
46 798 25.64 14.47
45 799 25.70 14.49
44 802 25.90 14.54
43 800 25.77 14.50
42 796 25.51 14.43
41 793 25.32 14.38
40 793 25.32 14.38
39 795 25.45 14.41
38 793 25.32 14.38
37 788 25.00 14.29
36 789 25.06 14.30
35 799 25.70 14.49
34 790 25.13 14.32
33 786 24.87 14.25
32 790 25.13 14.32
31 787 24.94 14.27
30 789 25.06 14.30
29 788 25.00 14.29
28 784 24.75 14.21
27 785 24.81 14.23
26 788 25.00 14.29
25 784 24.75 14.21
24 778 24.37 14.11
23 781 24.56 14.16
22 778 24.37 14.11
21 777 24.31 14.09
20 770 23.87 13.96
19 774 24.12 14.03
18 775 24.18 14.05
17 769 23.81 13.94
16 773 24.06 14.01
15 769 23.81 13.94
14 765 23.56 13.87
13 765 23.56 13.87
12 766 23.62 13.89
11 762 23.38 13.82
10 766 23.62 13.89
9 760 23.26 13.78
8 760 23.26 13.78
7 754 22.89 13.67
6 753 22.83 13.65
5 ERROR 3
4 756 23.01 13.71
3 753 22.83 13.65
2 751 22.71 13.62
1 755 22.95 13.69
I got a chance to try a few 50yd and 100yd shots today to go along with some 20yd tests I did the other day. Keep in mind that I’m not steady enough to ever be precision shooter, so just assume the gun is being penalized for having me holding it 🙂
20 yd was just Crossman 14.3 Premier pellets. The 50 and 100 yard “groups” (100yd is more of a loose gathering) were JSB 18.13. At 50yd, the group is 1″, or 3/4″ if you throw out the one flyer. At 100yds, it’s about 2.75″, much of which is my fault I’m sure.
Overall, I’m not sure I could expect much better for the money.
Cheers,
Rusty
Not bad at all for its price! I like to get mine to shoot as well as my BSA does at 50 yards, 1/2 groups. Even 3/4 at 50 yards, I would be happy with it. Based on the .200″ CTC groups I was getting at 25, I like I can get there with the stock barrel. I didn’t know what to expect from Kral, but I am liking what I see.
Greetings,
I got a chance to try a few 50yd and 100yd shots today to go along with some 20yd tests I did the other day. Keep in mind that I’m not steady enough to ever be precision shooter, so just assume the gun is being penalized for having me holding it 🙂
20 yd was just Crossman 14.3 Premier pellets. The 50 and 100 yard “groups” (100yd is more of a loose gathering) were JSB 18.13. At 50yd, the group is 1″, or 3/4″ if you throw out the one flyer. At 100yds, it’s about 2.75″, much of which is my fault I’m sure.
Overall, I’m not sure I could expect much better for the money.
Cheers,
Rusty
Attachments:
Thanks,
Rusty
25 yards.
I noticed with this trigger, the preload of the hammer spring has a huge impact on the weight and feel of the trigger. Maybe a lighter spring and a heavier hammer could help with the pull. Things to test down the road.
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Thanks Lee for another great write up.
Polishing trigger surfaces will surely help to smoothen things out and the way you did it looks and sounds very professional.
Just one thought: these parts in airguns are very often surface hardened (of which the initial surface appearance might be a result), so taking off too much (hard to know how much that is in reality) might get you to the soft part of the metal. The effect would be your trigger wearing out over time.
You might want to keep an eye on it.
Of course it is always possible to harden the surfaces again.
For greasing, I usually apply a (veeeery) thin coat of moly grease on the surfaces, which usually helps a lot. Note the downside that grease attracts dust and dirt so regular check and cleanup.
Alternative is molybdenum disulfide powder (dry, no grease) which I often use for the hammer and hammer housing it slides in, works good on trigger surfaces as well.
Coming back to the action noise, if you hear a “pinnnnng” sound coming from the action, this most probably comes from the hammer spring. The material generally used is piano string wire, which is less costly for the same force than other material, but does indeed make what piano wire is intended to do – sound. An alternative would be a hammer spring made of stainless steel with similar specs concerning external diameter, free length and force. Usually you would need to increase the wire thickness to get a similar force to piano wire or increase length a bit. Downside of increasing length – and therefore preload – is the risk of valve bounce (inconsistent pellet speed and louder discharge sound).
The other sound is hammer slap. Well, not much to do here, it hits as it hits to open the valve, except for having it hit less hard, but there you modify the rifle’s output power / pellet speed again.