Pentagon barrel of the FX Impact

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fe7565

fe7565

Member
Oct 13, 2015
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VA, United States
I figured I post some photos of the pentagon shaped barrel end of the FX Impact .22. Also some history on the polygon barrels I was not aware of. Apparently, polygonal barrels seal better around the projectile.

https://en.wikipedia.org/wiki/Polygonal_rifling


Question: I guess a pentagon shaped "crown" is normal? Or the crown only looks pentagon shaped, and in reality it is perfect round? Not talking about the barrel end "rifling" which is clearly pentagon shaped.
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Only took it out shooting to the range once with JSB 18s, can't tell for sure yet about consistency because I totally messed up the scope shimming.. Had some good groups close to half inch but mostly over one inch overall. I know the pentagon shape is normal, just wondering if the crown itself is supposed to be round or follow the shape of the barrel (i.e. pentagon)..
 
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The above post is correct. (jgburks)

The OP's pic 2 shows the internal smoothly rounded 'humps' (rifling) created by the Smoothtwist process well.

But I have concerns about the finish / crown shown in the above (OP's) photos - they dont look to be the genuine article.

EDIT (3 seconds later).


IN FACT - they are shots of a cut-off / HACKED ST barrel.


The OP 'fesomething) is not a 'straight talker'.

 
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@BRS...it's not a cutoff barrel. Why would someone cut off a brand new $2K barrel? Appreciate your thoughts, but let's think logically and put the conspiracy theories away :)
Now, back to the question at hand: These are the photos taken by the iphone in the flashlight mode. For #2 photo I used "fill shadows" to bring out the details of the crown otherwise you cannot see the crown and the outside of the barrel at the same time. The light from the iphone is just plainly not enough. Does anyone know if the crown itself is supposed to be a circle or it conforms to the pentagon shape of the barrel? The most inner circle which is gray is the crown.

Uploaded a photo of the same barrel taken without the iphone's light.

 
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The ST barrel is mostly a smooth bore, but in the last 2 inches the profile is pressed into the barrel from the outside.
The last 2 inches (with 1/2x20UNF thread for a silencer) actually screws off, then you can see the markings of the "rifling" process. Totally normal for a ST barrel.

Watch the vid and find out :) :

https://www.google.be/url?sa=t&source=web&rct=j&url=https://www.youtube.com/watch%3Fv%3DV_HTQwrTG6s&ved=0ahUKEwizgdzN_5TMAhUCaxQKHXF2Bx0QtwIIIjAD&usg=AFQjCNGslPNFaHJdcm6HPl4av8P35TLT8Q&sig2=HJaMlf5cFTrlde_YcxQZjg
 
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You know whats funny about that video, the claim that the smooth twist barrel is FX's idea. It's not. Another air rifle which started being built in the early 1900's, known commonly as the swedish excellent shot lead ball from a smooth bore barrel with 2 inches or so of pressed rifling in the end. Just like FX barrels. So much for that claim huh.
 
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"John_in_Ma"You know whats funny about that video, the claim that the smooth twist barrel is FX's idea. It's not. Another air rifle which started being built in the early 1900's, known commonly as the swedish excellent shot lead ball from a smooth bore barrel with 2 inches or so of pressed rifling in the end. Just like FX barrels. So much for that claim huh.
Click to expand...
Please read this article, assuming it is correct, the difference between ST barrels and the one you are talking about is significant.
Tom Gaylord says it is cut rifled.

http://www.pyramydair.com/blog/2016/03/swedish-excellent-part-1/
 
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"I_Like_Irons"The barrel is crowned before the rifling swaging process. That is why the crown bevel looks pentagonal in shape, because it is, just like the muzzle end of the bore.
Click to expand...
Was just wondering, because grooved barrels have round crowns and in essence the twist added to the FX barrel by the swaging creates lands and grooves also. My understanding is that these "lands and grooves" kind of flow together up and down and not sharply raised in relation to each other. Apparently, this "crown" works...just wondered how the obviously not round outer edges of the crown do not effect the pellet as it leaves the barrel.
 
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I pointed an arrow to the outer rim of the gray color (enhanced photo) "crown". If this crown would be on a rifled barrel (i.e. CZ, Lothar Walther, etc) it certainly would be of concern that is not a perfect circle and when the pellet leaves the barrel then the shape of the rim could affect it. However, all smooth twists must be like this so apparently it's a non-issue.

 
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