Tuning .25 cal FX Crown MK 1 Gen 2

[perazzisc3]

What might the fastest speed a stock .25 cal FX Crown MK 1 Gen 2 600mm barrel push the jsb diabolo exact king heavy mkii .25 cal 33.95 gr?

 

[18.13]

870-880

 

[perazzisc3]

what reg pressure and was the hammer spring maxed?

 

[18.13]

Reg at 148 and yes 

 

[Long_Gun_Dallas]

Sounds about right. Port and probe work should get a nice gain here. I'd recon 50fps 

 

[perazzisc3]

Would a dual transfer port installed with 148 reg and maxed hammer spring increase fps?

 

[18.13]

I just turned my Maverick from single port to double port and gained 45fps with the 34gr without out changing the tune 

 

[perazzisc3]

what was your reg pressure and hammer spring tension?

 

[18.13]

The maverick is a different beast with a larger plenum I don't know if it would apply to the Crown 

 

[Long_Gun_Dallas]

The dual ports are not all created equal, and they are usually less than ideal. I have also seen some fail/break. You need a probe that is cut to match the new port dimensions as well. Some report loss of power using them, Very few match what I see in optimal hand ported gains.

I havnt done 25, but one of my friends has with my guidance. I've done several 22 and one 30 on a Mk1 (gen3) crown

22s pick up a range of 50-75fps starting with 380mm and topping out at 75fps with 700mm.

My 600mm 30 picked up 22fps (4fpe) for a total of 85 @925fps. Not a lot to improve on the 30, but still good to see gains. 

 

[perazzisc3]

I purchased the ernest rowe dual transfer port and after gathering info I am a little reluctant to install. I am pushing the 33.95 gr JSB at 855 fps with reg set @ 145 bar.

I was hoping to get up to 875 - 890 fps with the dual transfer port but I may lose fps.

 

[Long_Gun_Dallas]

Crown hammer weight is a bit anemic. I use an added 7gm weight for heavier projectiles. One of my friends uses around 12gm. Just have to make sure to never dry fire it. You may still be able to buy custom weights on ebay. If you do use one, you have to trim the factory hammer spring guide to use it. I have a spare that is unmodified. I also use 150bar with the 7gm weight. Normally (without) I use 125bar with 18.13gr pellets. 

 

[1a2a3m4p]

Hola, mi MKII en 380mm en .25 escupe 25.39g a 875 fps con 120 bar y el resorte en 19, con puerto de transferencia dual y en máximo y sonda de pellet.....