Tuning Kral Jumbo pressure questions

[Dr. Kralenstein]

Finally ported and installed the full length rifle barrel and it only gave me an extra 35 fps with the air arms 25.4s. Those do around 840 fps with the 16" barrel, and only hit 875 high, averaged 870 with the 22" barrel. Not really worth it for the added length, I like the more compact looks of the rifle. 

 

[Dr. Kralenstein]

Decided to swap the 12" NP-02 barrel on that I haven't tried since the port job. It's doing 815-820 fps with the same air arms 25.4s. Think I need more hammer spring to make use of these longer barrels BUT, I really like the compact 12" and 7" Koi on the front. Perfect for backyard bunny busting! 

 

[Vetmx]

Be happy that you have a big old bottle supplying your needs. I’m dealing with a short barrel and short tube. The fill and refill parameters are tight. No joke, I could actually use a digital gauge. 

 

[Dr. Kralenstein]

I can only imagine, im getting 40 shots in my curve with the bottle. I've got 3 mags for the .25 caliber so I just refill when those are empty. I'm calling this one done for awhile, just shoot it and be happy. Too many other guns in the works right now.

Good luck with your project VetMx!

 

[Vetmx]

Troy keeps coming by in his lifeboat every time I start to go under. I promised myself I wouldn’t stick a reg in this XS but if it weren’t for him I lose patience and do a full conversion probably. I want one simple unregulated gun like the Urban I set up for my buddies son. I love that thing. Fill to 3k and shoot three mags. First shot always spot on.

 

[thammer]

I can only imagine, im getting 40 shots in my curve with the bottle. I've got 3 mags for the .25 caliber so I just refill when those are empty. I'm calling this one done for awhile, just shoot it and be happy. Too many other guns in the works right now.

Good luck with your project VetMx!

I get almost 50 shots at 50fpe from the Jumbo. 30 shots at over 60fpe. That's from the full length barrel though. 

 

[Dr. Kralenstein]

I can only imagine, im getting 40 shots in my curve with the bottle. I've got 3 mags for the .25 caliber so I just refill when those are empty. I'm calling this one done for awhile, just shoot it and be happy. Too many other guns in the works right now.

Good luck with your project VetMx!

I get almost 50 shots at 50fpe from the Jumbo. 30 shots at over 60fpe. That's from the full length barrel though.

I havent even touched the hammer or spring yet, it's completely backed out right now. Definitely have room for improvement, I'll revisit it one day. I still have my mega to put my huma reg in and buying an NP-03 to play with soon. Also have a gauntlet 25 project going on, and an akela and kratos I'm swapping calibers in to make the pup a 25 and the bottle gun a 177.

 

[Dr. Kralenstein]

Digging this back up. Since I have my NP03 down for fixing a torn o-ring I boogered up when installing my Huma reg in the 330cc tube, I decided to swap hammers with my jumbo.

Wow... they are definitely different.

The NP and mega use the same shorter hammer with a larger bore for bigger springs. This also allows the hammer to be drawn back further to compress the spring more.

Most I could get before with this jumbo in 25 cal was 840 fps with the 16" barrel and jsb kings. I installed the NP hammer and original mega spring and so far I'm getting 900-915 on a 3250 psi fill! My goal of 900 has been reached so thats exciting!

I dont understand why Kral didn't use the same hammer across the board for their guns since it makes this one perform way better. If I still had the full length rifle barrel I could see hitting 950 a reality.