FX Impact Pellet Spiral - Possible Root Cause Found

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Thank you. I've been scouring the web for a solution and this might be it. What is disconcerting is that the gun literally just came back from repair. They replaced the probe screw (not really sure why), increased reg pressure, adjusted the magazine opening, and accurized the barrel. For a gun that's about a month old, that stuff should have been done before it left Sweden? Either way, thank you for the link. I am going to go through it and see if I can figure it out. Thanks again..
 
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"Ginuwine1969"Why would a transfer port alignment issue cause inaccuracy? Doesn't that just control the flow of air into the barrel that the regulator is supplying? If there is a transfer port issue you should see that with a chronograph (FPS being low or all over the place)???


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It shouldn't.
I only suggested ensuring the transfer port was aligned as a means to ensure the barrel was properly aligned in the breach block.

Yes, the size of the transfer port does influence the flow and volume of air released into the barrel directly behind the skirt of a seated pellet when a gun is fired.

A misaligned transfer port occurs when the of the transfer port's circular opening is not centered with circular cutout in the bottom of the barrel that sits directly above the transfer port. This would restrict the flow of air (whether regulated or unregulated) that is released from the air reservoir when the gun is fired. A drop in pellet velocity.is the end result.
 
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Hello all ,
i see this post is old, but like you i'm owner of fx impact and the spiraling problem appear with heavy mk2 only, 
what i do is to polish inside the breech before and after oring (of course i removed the oring first) and now the pellet feed perfectly in the breech and no spiraling problem at all even at 150 yards. by the way i have opened the transfert port to 6mm and finely polished the inside , now is perfect

visibly smooth twist barrel are really created to shoot 25.4 grains pellet, now the heavy load in the breech in the same way than the 25.4 grains

have a good day all

Thierry
 
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"mag_de_mars"Hello all ,
i see this post is old, but like you i'm owner of fx impact and the spiraling problem appear with heavy mk2 only, 
what i do is to polish inside the breech before and after oring (of course i removed the oring first) and now the pellet feed perfectly in the breech and no spiraling problem at all even at 150 yards. by the way i have opened the transfert port to 6mm and finely polished the inside , now is perfect
visibly smooth twist barrel are really created to shoot 25.4 grains pellet, now the heavy load in the breech in the same way than the 25.4 grains
have a good day all
Thierry
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Are you talking about the inside of the barrel where the pellet feeds in and where the transfer port is? What did you use to polish it?

How much additional velocity/power did you gain with the 6mm port opening? What was the transfer port size before you opened it?
 
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yes i talk where the pellet feed, just removed the inside oring, i use sanding paper 2000 to do the job and for a good finish an old product called Mirror for copper use
concerning transfert port the original was 4mm and the max setting regulator (150 bars valve set 4) give me 250 m/s
today with a 6mm transfert port and a reg setted to 130 i shoot mk2 at 255 m/s
 
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just a quick overview of the capacity of the Impact,
i have 3 days of work on the barrel 
it's a shame Fx airguns can't do this at factory, when we paid a rifle at this price!!!!

don't forget to work on the charger too, the spring is too heavy to properly extract the pellets.

1525439072_1169697365aec5a60349d34.89880896_IMG_20180504_140150_2.jpg

it's a 93 yards 3 shots group with 3 m/s wind 
the mk2 load now like the king standard
 
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