GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: skorec on October 14, 2017, 05:13:25 AM
-
After I have received Puncher I done quick inspection and testing and I have found out next main problems and features :
1. Too tick magazine was able to put into the receiver only very hardly.
2. Manometer always shows 150 bar independently of refilling.
3. Totally wrong accuracy 5 MOA have improved a little bit (2-3MOA at 77 yd ) after sending down edges inside chamber and removing front band between barrel and air tube. It was my mestake
4. Also first part 2” of bore lands are scratched .
5. I am not able to remove O-ring from barrel chamber .
6. Barrel twist rate is about 1:22” and no chocked ( 480mm x 14mm)
7. At paper manual I can not see that valve needle is waist as I saw at Breaker version probably along of increasing air transfer way . I have not disassembly this part yet.
……………….
8. 40 pcs. /JSB-10,3 gr. shoots around 23 FPE from 2900 to 2200 PSI
Just now I am managing new LW 23” barrel for it.
I have choised two best targets from ten.
-
Thanks for sharing, Peter. A little alarming you had to straighten a bend, and hearing the condition of the bore itself is a surprise, but if it can cleaned up maybe you can bring that accuracy down to 1 MOA.
-
For now only SS string seems to be OK.
Notice
I have done it before barrel disassembling and sanding down barrel chamber. I do not understand why speed has increased ( from 950 to 980 FPS ) after it .
...............
Before one hour I was trying to return band without O-ring and POI change independently that the band has 0,2mm space around hole barrel.
-
The two barrels I've had in mine were horrible inside, lots of machining marks throughout. I good polishing might help it out a bit. You may have had a misaligment issue with the transfer port that caused the velocity change. I've had a new choked .25 barrel blank sitting on the bench for a couple weeks now, but no time to install it...
-
The two barrels I've had in mine were horrible inside, lots of machining marks throughout. I good polishing might help it out a bit. You may have had a misaligment issue with the transfer port that caused the velocity change. I've had a new choked .25 barrel blank sitting on the bench for a couple weeks now, but no time to install it...
Thanks Matt,
I will do deeper inspection and polishing KP barrel if LW blank barrel stay in blank condition too long.
Yesterday evening it was really dead calm therefore I return back the stock barrel band also with O-ring and tasted accuracy. Is not too bad. Just I need to focus to velocity variation.
-
My machinist who made me .22 LW barrel without big problems before refused me yet to do also .177 LW barrel. He told me that is not able to do relieve at barrel chamber for O-ring.
Therefore I am planning to improve my stock KP barrel by lapping by using Rotenstone and tight fitting patch as advanced me at
https://www.gatewaytoairguns.org/GTA/index.php?topic=132127.0. (https://www.gatewaytoairguns.org/GTA/index.php?topic=132127.0.)
Yesterday I was testing SS for JSB 10,34gr that let me 4 Magazines ( 56 shots) :
Mag1 3050PSI - 20870PSI whit average speed 968 FPS
Mag2 20870PSI – 273PSI whit average speed 980 FPS
Mag3 273PSI - 2540PSI whit average speed 964 FPS
Mag4 2540PSI - 2180PSI whit average speed 950 FPS
I hope that some of upgrading valve have done by USA/GTA guys able me to shoot JSB Beast 16,2 gr with similar ( 900-950 ) velocity .
Which and were to buy ?
-
By next stock barrel inspection and hardly cleaning ( with PerchlorEtylen I removed a lot of black dirt ) I have found out that :
1. barrel has no any barrel chamber that means that bore start immediately at end of barrel.
2. transfer port/hole at barrel diameter is 4mm.
3. the shirts of pellets are still scratched a little bit and accuracy not increase to much.
Rottenstone is o the way.
-
Whether was a little bit better ( but not dead calm ) therefore I tasted my new barrel.
I Have shoot 6 magazines and it seams to be that first shoot from magazine is always bad.
Interesting also is that my barrel prefers higher ( 290-303 m/s) velocities .
-
I have forgot to mentioned that new barrel air transfer hole is only 3,5mm instead 4m original hole.
-
Stock valve + hammer and default hammer spring + preloading produce shooting string with acceptable variation 290-303 m/s for 5*14=70 JSB heavy pellets from 205b to 140b. Therefore I am avoiding hammer bouncing.
The question is if any balanced valve may improve shot string and stay at the same velocity 968 FPS with JSB 10,34gr pellets.
However softer spring and lower hammer strike can improve the trigger and accuracy and reducing noise.
What is your opinion ?
-
Today I have cowered barrel by head adjusting insulating tube to avoid corrosion.
-
I just have one question, why you forcing such a high speeds when we all know that's not good (in most cases) if you want to have accurate airgun?
I have Weihrauch HW100 FAC which can push the JSB Exact up to 1150fps (350m/s) but there's no accuracy, but at 790-890 fps (240-270m/s) its insane.
I know it's not 77 but 44y, but you can see what I'm talking about, gun wasn't even on rest or bags, it's just leaning on the fence.
https://www.youtube.com/watch?v=cH2sdGymc5o (https://www.youtube.com/watch?v=cH2sdGymc5o)
-
I just have one question, why you forcing such a high speeds when we all know that's not good (in most cases) if you want to have accurate airgun?
Because in my case : choked LW 605mmx15mm barrel is two times more accurate to use speed above 290ms !!!
See my targets patiently
-
One of my best grouping I made yet was done curiously at windy whether at average speeds 295m/s - better - 287m/s- poorer
Notice
I do not understand why speed drop a little bit about 2% after barrel reassembling because slieving . May be I need to find out any silicon grease ( NOT oil ) to seal up better barrel into receiver .
-
Today I found out horrible Puncher issue.
Thin part of bolt probe on my Puncher is too short. Only 5mm.
To pushed all types of pellets enough deep it have to be min 3mm longer.
Can you please measure it at your Puncher
-
I bored 1mm hole, add self drilling screw and fixed it by tin.
-
Can you advice me how to stiffening first part of barrel direct before receiver.
Free floating LW 605x15mm barrel is shooting very well but POI Is changing a little bit ( approximately sub MOA ) .
I am thinking to add some 10cm prolonging chunk fixed to the receiver with four M5 screws.
Did you see somewhere similar or better barrel stiffening for firs part of free floating barrel ?
-
I try to ask my mashinist for next chunk
-
20 shots direct from tin .177 JSB Exact Heavy at 295-305 m/s at very slow wind at 71m distance.
Three ( F1,F2,F3 ) fliers rather then pushed
-
6mm shorter but stronger hammer spring let me more power and more shots.
The gap of not cocking hammer to the valve stem is 4mm.
My new spring is ( better more tunable will be ) :
length 58mm ( 55mm )
cross size 11,5mm ( 12mm )
wire thickness 1,4mm ( 1,4mm )
number of twist 20 ( 10-12 )
-
I have added four M5 screws at 7mm at front of breech for additional stiffening the barrel inside the breech. I hope it increase accuracy.
I am also thinking to add CF sleeve at first ( from breech to barrel band ) 40cm part of 60 cm barrel.
Which CF sleeve 400mm x 15mm inside OD 20mm otside OD you recommend me to buy ?
-
Today I have to repaired my Puncher
-
Today I have to repaired my Puncher
Thats pretty common and why we made a upgraded handle for the Kral.