FX IMPACT .25 ?'s

Not sure what the twist rate is, I would like to know that too, but I have the .30 caliber impact and the polymags do not fit in the magazine, so I feed them in one at a time single shot if I use them. Hope this helps

Polymag does not fit the magazine and not accurate for 75 + yards range

"GQ"Polymag does not fit the magazine and not accurate for 75 + yards range

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How accurate out to 50yds? 25yds?

50 yards can be not regular grouping,,,1.5 inches I would say
25 will be .30 inches or tighter

Twist rate of the few inches of rifling in the end of the barrel is 1:16 The pellets skid through this part of the barrel and don't full engage with the rifling so it can vary. Can pick up as little as 1/3 of the twist rate. For ballistic calculators I use 1:30 Pellet weight and speed will give differing twist rates. 
I think it's R/H twist. Someone else may know for sure. 

It is left hand twist. Harry (yrrah) did some investigation about the twist rate, it is posted somewhere on this forum. Interesting stuff.

Thanks Gijs. Here is a link to Harry's post. http://www.airgunnation.com/topic/twist-rate-of-fx-smooth-twist-barrels/
Managed to post on that tread by accident... Now it back on page 1. 
Got fat fingers. 
Michael