Kral Jumbo .25 owners! What type of regulated FPE are you getting?

[Tonio]

I have a Kral Jumbo in .25cal and was curious to know what others FPE was in .25cal regulated?

I'm in the process of regulating my Kral and hoping to get JSB 33.95gr to do around 880fps. 

Thanks 

 

[Odoyle]

You are better off running it unregulated if you want that kind of power.

 

[Tonio]

The reason I've asked is because I've seen Steve videos at Air Velocity Sport on the Kral. He was able to get in that range. With some of Troy Hammer help.

So, I was wondering if others are getting similar results. 

 

[Odoyle]

That's incredible if that's possible surpassing factory unregulated power levels. Very interesting! I have a regulator for a Kral bottle gun (haven't bought the gun yet but bought a regulator first) to actually lower the power as intended though for more shots. Quite the opposite as you seek.

 

[Long_Gun_Dallas]

I believe that gun was running a custom balanced valve. And also had the ports opened up.

 

[Vetmx]

I regulated my Jumbo .22. When you regulate a unregulated gun you go as big as you can with the porting. Like 80% of the caliber. Get rid of the hammer bounce then lighten the hammer because a unregulated gun has an insanely heavy hammer. If you do all this with a reg setting of 150b, you will have a powerful gun. How powerful? Do it and find out. It will be a better gun regardless. Much nicer to shoot and it will sound crisper. 

 

[Tonio]

@Vetmx - I'm using a Huma reg. and since the pellet .25 caliber pellet is 6.35mm. I cannot go beyond that...in fact it will have to stay a little but less than 6.35mm. Thinking 6.0...

I was also wondering if anyone is having problems with cocking pin searing, it's not hardened?

 

[Vetmx]

80% of 6.35mm is 5mm. That’s the max I would go so you don’t experience loading problems. 

 

[Vetmx]

My cocking pin kept working loose until I put a drop of blue loctite on it. Looks like yours was loose and you didn’t notice until it was too late. 

 

[Ex.Magnum]

I regulated my Jumbo .22. When you regulate a unregulated gun you go as big as you can with the porting. Like 80% of the caliber. Get rid of the hammer bounce then lighten the hammer because a unregulated gun has an insanely heavy hammer. If you do all this with a reg setting of 150b, you will have a powerful gun. How powerful? Do it and find out. It will be a better gun regardless. Much nicer to shoot and it will sound crisper.

Ever tried slugs? Nielsen or other? Tight groups?

 

[Vetmx]

No. I built the gun as a volume shooting pellet gun. Didn’t feel like trying 10 different slugs at 20 different velocities. Slugs involve a lot of lead, adjusting, and shooting at all distances. I’m kinda burned out on that now. Pellets always perform without drama and the Kral barrels generally don’t disappoint. 

 

[Tonio]

Yes, lead can get expensive, so slug are out of the question for me and this setup. I really like the accuracy of my Kral barrel out to 50-100yrds. 

 

[Parrotculler]

The Heavies are departing my .25 barrel at around 730 fps with a regulator set point = 120 bar. That (highly accurate + efficient) power is enough for me at this time. I doubt I would even need to crank the reg up beyond 140 bar to achieve your target speed.

The dirty secret of this Kral is the following combo:

- 58 cm barrel enabling higher power;

- the plenum size became quite generous with my paintball reg + adaptor set up. The adaptor acts as a type of power plenum. This set-up inevitably moved the bottle forward. I use the resulting space to store my shooting log . This being a long gun (especially with the recommended silencer), it remains well-balanced. See it being sandwiched between 2 FX Royale's below.

- the enlarged ports (5mm -- oval in the barrel!). This porting is easy enough but you need to overcome the power adjuster limitation (limited diameter). Replacing the stock power adjuster by a self-made one out of an 8mm allen bolt was not the end of the world, even for a non-metal worker like undersigned.

Vetmx did a highly informative thread on his Jumbo project -- that together with another thread about SSGs got me started. THammer thankfully weighed in with his twin hammer spring, which has great effect. AirgunVelocitySport's Jumbo vids are also worth watching. 

 

[Tonio]

@Parrotculler How many shoots are you getting at 120 bar? What was your shoot deviation and spread?

 

[thammer]

With the Pro500 I'm getting a a tight 50 shot spread unregged at 880-900 fps with the 425cc 2900psi it is closer to 30-35 shots at 900fps. All with 33.95gr MKII Heavies.