Crown upgrade from .177 to .25

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Gambler

Gambler

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Feb 20, 2023
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Hi. Im thinking about order a .25cal kit to my crown mk2. But do I need something else than what comes with the probe, liner and shroud?
Hammer spring or heavy hammer to get to the dessired speeds that .25 need?
I cant see im getting near ok speeds with .25 when I only get 850fps with 13.4gr .177 (but my tune is probably way off i hope)
I Just want to know so I can order the parts i need at the same time.
 
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madeintheuk said:
The magazine does not come with the kit, so unless you’re single loading, you’ll need one.

The hammer spring is the same unless you have sub12 crown, and it is more than capable of pushing the 33gn jsb’s at speeds upwards of 900fps with the 600mm barrel.
Click to expand...
Yeah mag i need :) but I dont see how I can push 900fps with 33gn when I can do it with 13.4gn xD
 
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I have a 22 and 25cal Crown. You will need to set the reg at 150 and adjust the internal hammer spring to almost max, not quite max, but almost to get 65 foot pounds advertised by FX. From the speed you currently have in .177cal, it sounds like it's not set at max with the IHS. You should be getting 26 foot pounds out of the .177cal.
 
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Gambler said:
Hi. Im thinking about order a .25cal kit to my crown mk2. But do I need something else than what comes with the probe, liner and shroud?
Hammer spring or heavy hammer to get to the dessired speeds that .25 need?
I cant see im getting near ok speeds with .25 when I only get 850fps with 13.4gr .177 (but my tune is probably way off i hope)
I Just want to know so I can order the parts i need at the same time.
Click to expand...
I'm not experienced as my Crown hasn't even been delivered yet, but I'm looking at the changing calibers as well. Mine is a .30 cal. The only thing other than the barrel kit that I'm aware of is a magazine. I think the Mk2 adjustability covers all the calibers, but I guess the long range .30 cal slugs, and the arrow launchers apparently benefit the heavey hammers?
 
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madeintheuk said:
The magazine does not come with the kit, so unless you’re single loading, you’ll need one.

The hammer spring is the same unless you have sub12 crown, and it is more than capable of pushing the 33gn jsb’s at speeds upwards of 900fps with the 600mm barrel.
Click to expand...
My MK II 25 would shoot 34 gr H&N slugs right at 900 fps. It was about all it could do with the stock hammer weight. I had the IHS adjusted to max.
 
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steve-l said:
The .177 Crown has a poor reputation for some reason unknown to me. I have a .177 conversion that I bought years ago and never used. My Crown was delivered in .25 and performs very well, except for the POI shift which a barrel band resolves. All you need is the shroud, the barrel and the probe. All of which comes in the kit.
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I have been studying Crowns prior to purchasing one, and never heard of a bad reputation, POI shift problems, or a need or use of a barrel band?
 
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Gambler

Not sure what barrel length you are looking at, but my MKII (Skeletor) with a 600mm barrel shoots the 34 grain JSB's with no issues at 900 FPS. Pull the rifle from the stock (Careful lots of little parts under the hammer spring wheel) and put your hammer spring wheel to max and adjust the 1.5 allen screw until you have very little play left and set the reg to around 150. This should get you above 900 FPS with the 34's then it just comes down to finding the right FPS your barrel likes. Skeletor loves 900 FPS, I tried lower and higher speeds, but nothing was as accurate as 900 FPS in my rifle.

Hope this helps

Tony P.
 
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steve-l said:
The .177 Crown has a poor reputation for some reason unknown to me. I have a .177 conversion that I bought years ago and never used. My Crown was delivered in .25 and performs very well, except for the POI shift which a barrel band resolves. All you need is the shroud, the barrel and the probe. All of which comes in the kit.
Click to expand...
i went from 22 cal to a 177 in my crown it shoots great what was your problem
 
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pesty3782 said:
Gambler

Not sure what barrel length you are looking at, but my MKII (Skeletor) with a 600mm barrel shoots the 34 grain JSB's with no issues at 900 FPS. Pull the rifle from the stock (Careful lots of little parts under the hammer spring wheel) and put your hammer spring wheel to max and adjust the 1.5 allen screw until you have very little play left and set the reg to around 150. This should get you above 900 FPS with the 34's then it just comes down to finding the right FPS your barrel likes. Skeletor loves 900 FPS, I tried lower and higher speeds, but nothing was as accurate as 900 FPS in my rifle.

Hope this helps

Tony P.
Click to expand...
Ty ill hope for those speeds too, but I have tried the IHS on max and 150bar and i get slower speeds with that than 135bar, but I have 500mm barrel in .177. I think I go with 600mm in .25 :)
But this is what I was kinda worying about sice i cant get to 900+ with .177 how am I gonna get there with a much heavier .25 pellet/slug xD
 
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Gambler said:
Hi. Im thinking about order a .25cal kit to my crown mk2. But do I need something else than what comes with the probe, liner and shroud?
Hammer spring or heavy hammer to get to the dessired speeds that .25 need?
I cant see im getting near ok speeds with .25 when I only get 850fps with 13.4gr .177 (but my tune is probably way off i hope)
I Just want to know so I can order the parts i need at the same time.
Click to expand...
 
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Gambler said:
Ty ill hope for those speeds too, but I have tried the IHS on max and 150bar and i get slower speeds with that than 135bar, but I have 500mm barrel in .177. I think I go with 600mm in .25 :)
But this is what I was kinda worying about sice i cant get to 900+ with .177 how am I gonna get there with a much heavier .25 pellet/slug xD
Click to expand...

Hi Gambler,

It sounds like your only experience with the Crown is with .177…

When you get your .25 barrel and kit, you will notice that the .25 barrel has a much larger transfer port opening - allowing for much more airflow into the barrel.

This larger opening will allow you to get 900fps in .25 - using your existing hammer and hammer spring - even though you currently can only get to 850fps with the 13.4g .177. It sounds like your stock FX .177 transfer port size is limiting you.

I think this addresses your original concern in this post…

-Ed
 
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Gambler said:
Just a tought, I see there are transferports i can buy and put on my barrel, but is there any mod/DIY that i can try first ? Drill out 2 holes on each side of the existing or something?
Click to expand...
The barrel kit comes with a pellet port and a slug port. You will be able to get to 900 no problem. I have my reg at 115 hammer wheel on 17 and getting 900.
700mm
 
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