Results after TJ barrel install on my Kral Bighorn.

[Roachcreek]

I replaced the Oem barrel on my Kral Bighorn it was a 18 inch dechoked barrel. My TJ is 28 inches. The kral’s 18 inch barrel was shooting 44.5 grain bullets at a one shot high of 940 fps, but ranged down around 910-920 fps.

The Kral Bighorn has Troys tune .24 tp and the hammer altered to use Bulldog springs and the valve return spring removed. I am using a heavier Pitbull spring and the 3625 psi tank has been replaced with a 4500 psi .5L cf tank.

After the barrel change the first string was after turning the hammer spring out two turns, 1021,1049, 1030, 1035,1023,997,997,943,917. Starting pressure from a .5l 4500 psi tank was 4200 psi, ending pressure is 3300 psi. The first 7 shots are not too bad, but it drops off fast. 9 shots averaged 1001 fp/99 foe.


The second string was shot after two more turns out on the hammer spring.
929,997,989,981,987,987,980,1009,998,975. Starting pressure 4200 psi ending pressure 3500 psi. This string shows a bathtub string clearly. Average velocity 983//95.5 fpe.

I had planned on returning the VRs, but not so sure now. I might try turning the hammer spring back in for the next string.

Regards,

Roachcreek

 

[Motorhead]

Making the power .. just at really high pressure/s ....

 

[Roachcreek]

Yes it indeed is higher pressure, 575 psi higher. I did’ ask Troy about this and he saw no problem. I am using a 4500 psi tank also.

I can’t recommend it for everyone, but it works for me.

Regards,

Roachcreek

 

[Dr. Kralenstein]

Nice numbers @Roachcreek

I too, run a 4500 psi fill on my 25 cal jumbo. Tops out about 60 fpe with 33.95 jsb for 40 shots. I keep it at 60 shots for 52 fpe though. Smoother cycle and much quieter. This is with a 16" barrel and the smaller valve and drop block the jumbo has vs the bighorn.

My krals are very accurate, but they definitely need higher pressure to get a good shot curve with higher power. I haven't done anything to the valve besides port match everything to 3/16". Barrel, valve, and transfer passage.

 

[Roachcreek]

Thanks for chiming in Doc, I felt a kindred spirit when I read your posts about higher pressure in the Krals. I have a kratos that I ported to .20 and exchanged the 3000 psi tank for a 3625 psi tank. I hit 62 FPE with Kings, but went back to the 3000 psi fill tank when I put the 3625 psi tank my Texan LSS 257.

I turned up the power one full turn and I cleaned the barrel and lightly polished with Flintz.

WOW.

10 shots at 4100 psi as my fill tank runs down, again no valve return spring, same 44.5 grain bullet.
1053,1043,1043,1035,1016,1036,1031,1021,1030,1024. A typical beautiful Kral cliff string that keeps new Kral shooters asking,”are the Krals regulated?” Starting psi 4100 ending pressure 3500 psi.-

1033 average velocity 105.5 FPE.

I think I am done. Well maybe see what a second magazine will do.

Regards,

Roachcreek

 

[Roachcreek]

Lowered the fill pressure to 3800 psi. Same 44.5 grain cast bullet.

1054 3800 psi starting
1037
1045
1051
1045
1052
1045
1035
1024
1023 ending 3400 psi

Average velocity 1041fps/107 FPE

Looks like I can drop pressure and still meet my 100fpe goal.
1018 3700 psi fill
1013
1026
1019
1043
1021
1003
1019
940
9 shots, the chronograph missed one averaged 1011 fps/101 FPE.

It appears that a normal 3625 psi fill will result in 100 FPE. Many folks get nervous about exceeding recommended fill pressures, not so much for me as I am running a 4500 psi tank. However if you own a Kral Bighorn that Troy Hammer has performed his Kral magic on, with a 28 inch 1-14 .250 groove diameter TJ barrel you can expect 100fpe

As for myself, I will go with the 3800 psi fill, 175 psi over the factory fill and feel perfectly safe. That fill will give me a trjectory of around -2.25 inches at the muzzle/100 yards with a rise above the crosshairs of 2.25 inches. And that is one hell of a flat shooting Airgun.

Regards,

Roachcreek