.25 kral puncher tuning

Hello all, hello Bob,
first of all i wish you an Happy New Year to everybody and your family.
very good health is the most important.

I come to you with my new toy coming back from tuning a basic Kral puncher breaker wood 6.35
I’m coming to this model because is not expensive for a bullpup model

concerning tuning on the rifle the first is the barrel
original barrel was removed and a lothar walther unchocked 600 mm in place  (248 land  254 groove)
the air propellant system is totally rebuild beginning by the filling system
the valve lost 33% of weight in the operation.
hammer and spring totally new, hammer lost 50% of weight too and spring is harder than original.
transfert port on all air circuit opened to 6mm (.236)
power selector removed and changed with one bigger with 6mm hole the total speed variation between high and low is 70 m/s (approx 220 fps)
the regulator is made from a gunsmith here not a serial model the speed variation is only 5 m/s
the air chamber is 65 cm3
the pellet loader is rebuild too because bullet is harder to load and need more efficient material.
trigger is tuned too, fire at 200 grams load

concerning power and speed
jsb 1.640 grams pellet travel at 355 m/s (1160FPS) who is very too high for it  best accuracy at 290 m/s
jsb 2.2 grams pellet travel at 300 (980fps) too high too, strangely i need to reduce more to obtain perfect accuracy  275 m/s
NOE bbt 52 grains bullets travel at 260 m/s (850fps) not tested yet for accuracy but seem to work fine

following pictures are 10 shoot group at 55 m with jsb 2.2 grams setted at 275 m/s
ten shots in the central dot and one pellet in each vertical dot

following picture is penetration test with NOE bbt bullets. same distance 55m shots on aluminium 3mm
2 groups of 4 bullets each how you can see only 3 holes for each group
on target one square is 1cm2

the power with BBT bullet is 115 joules (85 fpe) and great accuracy (this is my first shot series with this rifle and seem very promising

i’m happy to share with you on this great forum where i learn a lot
thank you very much to all and particularly to Bob for all i can learn here

Thierry