I just ordered an fx crown in 25 cal from Utah Airguns. I asked them to see if they can adjust the gun to shoot the jsb heavies MK2 around 900 fps. Has anyone ever done this. How is accuracy at this fps. They said they can adjust it for me no problem.
FX Crown 25 cal.
- Thread starter Zeringue
- Start date
Ernest got the jsb Heavies to 900fps but it is not within the guns normal operating parameters. As Ernest says don’t do what I’ve done you will void your warranty. Maybe send him an email.
Personally I think until a liner with a twist rate specifically for the heavy pellets is available the results won’t be optimal. The 1:28 twist rate is for the 25g normal kings and it’s performance with that pellet are outstanding.
People are shooting the Heavies well but not quite with the same accuracy as the normal Kings.
When Steve did his resent review he showed good groups at 50y but when it came to the 100y
test he shot the normal kings again.
Michael
http://www.airgunnation.com/topic/fx-crown-25-33-9-mk2-at-900-910-fps-groups-free-single-shot-tray-giveaway/
Personally I think until a liner with a twist rate specifically for the heavy pellets is available the results won’t be optimal. The 1:28 twist rate is for the 25g normal kings and it’s performance with that pellet are outstanding.
People are shooting the Heavies well but not quite with the same accuracy as the normal Kings.
When Steve did his resent review he showed good groups at 50y but when it came to the 100y
test he shot the normal kings again.
Michael
http://www.airgunnation.com/topic/fx-crown-25-33-9-mk2-at-900-910-fps-groups-free-single-shot-tray-giveaway/
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I'll 2nd what Michael said. Mine was just amazing with the 25 grain. 75 yard groups were one ragged hole. At factory it shot 34's about 790 fps. Grouped ok but not so good as 25's. Adjusted the speed up on the 34's to 840 fps was my best accuracy. It was damned respectable, but didn't quite match the 25's at factory setting. I set everything back to factory settings for now and am going to wait until they release a faster twist rate liner. Sylvan
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Hi
Speed increase of pellet is not necessarily going to give more accuracy. So why that requirement?
Also means more wear on parts, maybe invaldate warranty, less shots per fill and would surmise complete shot string inconsistent.
One of the best books written on shooting " Use enough Gun" . Says it all. If it is more hitting power on target go up a calibre.
Lucky to have the Crown, mine due in January .25.
merry xmas too
Safe shooting
Speed increase of pellet is not necessarily going to give more accuracy. So why that requirement?
Also means more wear on parts, maybe invaldate warranty, less shots per fill and would surmise complete shot string inconsistent.
One of the best books written on shooting " Use enough Gun" . Says it all. If it is more hitting power on target go up a calibre.
Lucky to have the Crown, mine due in January .25.
merry xmas too
Safe shooting
Upvote 0
Never ran a full shot string and counted the shots. Was working on accuracy with the 34 grain MK-II's and when couldn't attain what I wanted went back to the factory settings. Do remember that it was set so Max power setting was giving the 840 fps with the 34 grain and and then with power adjuster turned down to 4 it was giving me 880 fps with the 25 grain. It will be interesting to see when the faster twist liners are available if they will still shoot the 25 grain with same accuracy as the slower twist liner. sylvan
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Sounds good. I had Utah Airguns tune it up for me. The adjusted the regulator up for me. But I will see when I get it how it is shooting. I may drop the regulator down a bit to be able to shoot the 34 grains. Around 840 to 850 and shoot the 25 grains at a good speed. I think UA said they set the regulator at like 145/150. So I will see when I get it. My gun is on its way now it’s just a waiting game and it’s killing me. UPS has not updated my tracking yet so I don’t know where the gun is.
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It's funny how waiting for Brown Santa to come is almost painful 
It seems to me that a higher twist rate is going to take more energy to force the pellet through it and maybe rob a little of the fps. So even if we get it spinning faster, we'll lose some speed. Trying to regain that speed will cost some efficiency . I think it is going to be a tuning trade off.
Crusher
It seems to me that a higher twist rate is going to take more energy to force the pellet through it and maybe rob a little of the fps. So even if we get it spinning faster, we'll lose some speed. Trying to regain that speed will cost some efficiency . I think it is going to be a tuning trade off.
Crusher
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