Fx crown setup

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Gambler

Gambler

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Feb 20, 2023
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Hi, I picked up a .177 crown mk2 (500mm) on my way home from work today, got home and the first thing i was doing was meassure the fps on the pellets/slugs i have to see Whats best before sighting in my scope. And straight out of the box it shot "meh" 500fps with jsb monster. The reg was set at 110bar, port at high and 23 on the last knob. I have tried to adjust alot and mix things up, but if I increase the reg it only slows down, so now im down to 90bar and my best pellet/slug is jsb KO 13.4gr @ 750fps, thats about max of what I can get out of this, the monsters is around 720 on same setting. The accuracy is amazing and it shoots consistent and Nice. But something in me i think expected more after seen some YT vids of the Gherard guy shooting 20gr slugs with 177 crown with reg on 155bar, high port and low hammerspring and getting 850 fps but that is with 100mm longer barrel tho.

But very happy with it if this is the limit ofc.

20230511_151839.jpg
 
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Gambler said:
Hi, I picked up a .177 crown mk2 (500mm) on my way home from work today, got home and the first thing i was doing was meassure the fps on the pellets/slugs i have to see Whats best before sighting in my scope. And straight out of the box it shot "meh" 500fps with jsb monster. The reg was set at 110bar, port at high and 23 on the last knob. I have tried to adjust alot and mix things up, but if I increase the reg it only slows down, so now im down to 90bar and my best pellet/slug is jsb KO 13.4gr @ 750fps, thats about max of what I can get out of this, the monsters is around 720 on same setting. The accuracy is amazing and it shoots consistent and Nice. But something in me i think expected more after seen some YT vids of the Gherard guy shooting 20gr slugs with 177 crown with reg on 155bar, high port and low hammerspring and getting 850 fps but that is with 100mm longer barrel tho.

But very happy with it if this is the limit ofc.

View attachment 355651
Click to expand...
Congratulations,
I'm going to be right there with you.
Mine is headed this way in a delivery truck.
👍
 
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I took 2 full turns and with best result on 120bar and fps @ 820.
If I go higher than 120bar the fps start to drop, does that mean i have to turn it 1-2 turns more to be able to get reg at 150bar?

Edit: its hard for me to know where to set the baseline as he does in the vid cuz my knop has 1-23 and dont have the same shape has his
 
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Gambler said:
I took 2 full turns and with best result on 120bar and fps @ 820.
If I go higher than 120bar the fps start to drop, does that mean i have to turn it 1-2 turns more to be able to get reg at 150bar?

Edit: its hard for me to know where to set the baseline as he does in the vid cuz my knop has 1-23 and dont have the same shape has his
Click to expand...

It means you need more hammer . Not pressure.
 
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Increasing reg pressure mandates an increase in hammer strike to open the valve. At some point you run out of adjustment and need a heavier hammer, which is why some people install a larger or tungsten (heavier) hammer.

Goal is to find the reg pressure where the speed you want to shoot is exceeded by 3-4%. So, if you wanted 1000fps, find the reg pressure that gives you 1030fps and won’t go higher than that even if you increase hammer. The 1030 is the peak velocity for that reg pressure. You then decrease the hammer to get 1000fps and the theory is that you’re then tuned “on the knee” of the velocity curve, which gives a quieter and less angry shot cycle because it’s not wasting air/energy.

FWIW, in my three FX 177s (😳), which have the same liner as yours, Zan slugs are easily the most accurate and they shoot best between 920-980fps. I’ve been nerding excessively on 177 slugs for months. It’s pointless to try anything greater than 13 grains because FX liners don’t have enough twist to stabilize anything heavier (unless you’re at really high elevation).
 
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Well, now i adjusted and tried and failed and reset alot.
What I have Come up with that get me most fps is 135bar, high port and the internal hammer adjuster on max length. In that is most certanly wrong if I understand the guy in the vid right, but it gives me 880isj with KO 13.4gr and 750 with zan 20gr slug, 820 with JSB beast.
Its probably some way to make it better but I cant find it right now and my scuba tank i soon empty :/

Zan 20gr:
Paper target =50m
Orange Steel = 135m
135m is shot with holdovers at 10x, if I zoom in i dont have any holdovers left to use.

20230512_125120.jpg


20230512_125140.jpg
 
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Headshots said:
It means you need more hammer . Not pressure.
Click to expand...

Gambler said:
I took 2 full turns and with best result on 120bar and fps @ 820.
If I go higher than 120bar the fps start to drop, does that mean i have to turn it 1-2 turns more to be able to get reg at 150bar?

Edit: its hard for me to know where to set the baseline as he does in the vid cuz my knop has 1-23 and dont have the same shape has his
Click to expand...
The Power Wheel with the 1-23 settings is what I have. The range that represents in terms of hammer spring compression is about 4.2 mm in increments of roughly .2 mm. So to do a tune pick someplace to start. I picked a setting of 18. That means I can increase the hammer sping compression by 1 mm by turning the power wheel to 23. When I am tuning, if I have to adjust the power wheel up that high it means I need to add two revolutions at .5 mm/rev on the micro adjuster screw. Then I set the power wheel back to 18 and resume the process.

There is another step you can take. That is to add a hammer weight. All of the hammer weights for the Maverick also work for the crown, but you need to change the Spring Holder (part # 19902 - D3 on the Crown schematic) as the stock part will not allow for adding hammer weights. The easiest way to do this is to order the Crown Slug Power Kit from someone like Utah Airguns. It includes a hammer weight and the appropriate spring holder. Then you get to retune again!
utahairguns.com

FX Crown Slug Power Kit

FX Crown Slug Power Kit
utahairguns.com utahairguns.com

Lots of power available in the Crown. You just might have to work a bit to get it. Ultimately it is not as powerful as the Impact or the Maverick because it doesn't have nearly as large a plenum.

Cheers,
Greg
 
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