FX Impact puff leak

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When I shoot , i feel a puff air leack from the hole beside the regulator gauge.
Anyone can tell me witch ring I have to change ?

 
That's a grub screw that hold and aligns the valve housing. Orings around the valve housing 29B.
I'm not an expert but that would be my guess. Have a look at Ernst video on how to pull it apart. . Bit of work to get to them. Someone may be able to confirm for sure. 
http://www.airgunnation.com/topic/fx-impact-schematic-and-list-of-orings/

I just got the rebuild kit and did all of them in mine. 
Michael
 
I been testing Viton oring 1X2 and buns 70 side by side after a tin the Viton seem to swell up a bit and the 70 got smaller, don't know if it matters but I have less leak issue with the Viton. It's a habit for me to indicate the CS 1st, 1.02 CS will not fit. go by the web site details below:

http://www.oringsandmore.com/viton-fkm-o-ring-2-x-1mm-price-for-25-pcs/
 
"sniperlabyo"I been testing Viton oring 1X2 and buns 70 side by side after a tin the Viton seem to swell up a bit and the 70 got smaller, don't know if it matters but I have less leak issue with the Viton 

http://www.oringsandmore.com/viton-fkm-o-ring-2-x-1mm-price-for-25-pcs/
Thank you Ernest and gixxer3000 for those imformations
Now I am ready to order and install.
Without your videos and informations Ernest we would have to ship our Impact for maintenance.
Thank you
GQ
 
No more leak.
I have changed the o-ring following video from Ernest carefully with 100%"success.
I have appreciate the experience and that make me feel much more informed about the Impact.
Dont be scared to change o rings guys.
The Impact is a very accurate air gun and it is not a airgun for someone who wish to drive a Ford Tempo .
This is a Formula One and need maintenamce properly done.
For me this is lot of fun, havimg all my time and not rocket sience. Just simple mechanic.
Thank you again Ernest.
Without your video I would have be in a situation,to ship my impact for repair with shipping cost and manpower repair and servicing cost.
I just saved a bunch of money and did not have to wait 2-3 weeks for my gun to come back home , not knowing if they made the proper job.
Regards
GQ