.25 Crown maximum velocity

[stoti]

Without pushing the reg. to it’s max of 150bar and making adjustments to the washers what’s the best velocity any of you have been able to get out of the .25 Crown and the 33.95 JSB’s? I know BC varies on velocity but is .046 about right for the 33.95 JSB?

My gun shoots the 25.4 grain JSB’s great at about 925-930fps but when I switch to the 33.95, the velocity obviously drops to about 820fps.. They are very accurate, however, to really take advantage of the greater BC with the heavier pellets the pellets need to be pushed more than 820-825fps. I’m thinking somewhere around 870-880fps. I don’t have my ballistic calculator so that’s just a guess. Can that velocity even be reached with the Crown and the 33.95 grain JSB’s? 

Stoti

 

[ackuric]

Yes. Ernest Rowe is the man when it comes to tuning these higher end rifles.



Ideally you'd have the crown ported and polished to around 90% of the bore. My marauder (same barrel length iirc) regged at 135 bar is ported to .23" and send the 33.95's out at 900 fps peak, which is good for a 860-880 tune.



.045 - .046 is a good BC to use for the 33.95's when using ballistic calculators.

 

[HD2010]

I'm at 849 FPS tuned hammer spring. 150 bar and PW on B with a deviation of 2.53.

 

[ackuric]

He clearly stated he wanted to avoid approaching pushing the reg to 150 or more. 849 @ 150 is VERY short of what he is asking for. He wants 880 @ 145 or less I am sure...which will require re-working of the valve. Ernest Rowe would be able to work his magic on it no problem...

 

[HD2010]

He clearly stated he wanted to avoid approaching pushing the reg to 150 or more. 849 @ 150 is VERY short of what he is asking for. He wants 880 @ 145 or less I am sure...which will require re-working of the valve. Ernest Rowe would be able to work his magic on it no problem...

I was answering his question about max FPS.

 

[sniperlabyo]

With Fx Crown power tune the average speed with 33.9gn mk2 with 150b reg pressure:

500mm barrel 875-885 fps

600mm barrel 975-985 fps

700mm barrel 1030-1050 fps

each barrel has different bore tightness so speed will very.

FX Pit Stop

 

[stoti]

Thanks Ernest, glad to hear from you! I was hoping I wouldn’t have to send it in for a tune...yet. I have a slug liner coming and was hoping with a 31gr. slug and a B.C. upwards of .077, I wouldn’t have to push the slugs as hard to get the desired results. Maybe Around 850fps? However with a tune, the long range possibilities would be amazing.

Ernest if you could get my gun shooting the 31 grain slugs at around 1000fps, with a B.C. of .077, that would be an absolutely crazy, long range destroyer!!! I am getting excited just thinking of the capabilities. I’ll get a hold of you! Thanks, Stoti

 

[stoti]

Just punched in some numbers out of curiosity... Ernest said his tune could push the 25 cal. 33.95 grain JSB to about 985fps. Assuming the gun could push the 31 grain slug with a B.C. of .077 to near 1000fps. Drop would go from almost 60 inches at 150yds to 30 inches. Not to mention the capabilities in wind and retained energy down range! That is amazing and why these slug liners and slugs in general will be the new frontier in air gunning!

Stoti

 

[heavy-impact]

Just call FX USA and order Mr Rowe's power kit. It's that simple. 1-866-639-0772

 

[Centercut]

@heavy-impact, is there a Power Kit for the .22 caliber FX Crown?

Mike

 

[stoti]

I thought there was some machining,polishing or boring that needed to be done too. Ernest, can you weigh in please? Will a kit do it or is your tune more involved than that? Thanks!

stoti

 

[heavy-impact]

@heavy-impact, is there a Power Kit for the .22 caliber FX Crown?

Mike

I'm sure there is since Mr Rowe makes them to order. Doesn't cost much either.

 

[sniperlabyo]

Powe kit in any caliber include hammer weight, modified HSTA, hammer spring and larger bore VS, barrel TP long gated. 

The funest power mode is pushing .22 18gn supersonic speed of 1210fps with accuracy of 1/2” at 43y

 

[stoti]

Thanks Ernest. Actually, thanks everyone, I appreciate it!



Stoti

 

[DreamSmoker]

My crown can push those 34s as decribed. You just order the power kit and install. Takes five minutes..

$52 Bucks

You should also modify your regulator so you can take advantage of the higher pressures above 150bar..

 

[Bob_O]

Powe kit in any caliber include hammer weight, modified HSTA, hammer spring and larger bore VS, barrel TP long gated. 

The funest power mode is pushing .22 18gn supersonic speed of 1210fps with accuracy of 1/2” at 43y

This with the 500mm barrel?

 

[FearnLoading]

With Fx Crown power tune the average speed with 33.9gn mk2 with 150b reg pressure:

500mm barrel 875-885 fps

600mm barrel 975-985 fps

700mm barrel 1030-1050 fps

each barrel has different bore tightness so speed will very.

FX Pit Stop

Hi Earnest. Can this tune be achieved just by maxing out the hammer spring and putting the reg at 150? Or are there more steps involved. 

 

[Tomiboy]

With Fx Crown power tune the average speed with 33.9gn mk2 with 150b reg pressure:

500mm barrel 875-885 fps

600mm barrel 975-985 fps

700mm barrel 1030-1050 fps

each barrel has different bore tightness so speed will very.

FX Pit Stop

Hi Earnest. Can this tune be achieved just by maxing out the hammer spring and putting the reg at 150? Or are there more steps involved.

You need to buy the powerkit from Earnest

 

[sniperlabyo]

No, the hammer spring is limited/no strong enough to fully utilize 150b thats when the weight comes in to play, minimize heavy cocking forces don’t use stronger hammer spring.

 

[Bob_O]

Ernest,

I forgot where you posted the website that listed some of your custom kits.