Huma Duel port and probe question

[SniperM]

Question on Huma dual port and pellet probe on 25 cal FX Impact MK II. I installed both tested before install shooting JSB Heavies MKII speed was 905 avg for 10 shots 2 fps spread.

After installation same settings it 875 fps with 2 fps spread, question why the slow down Iam puzzled anybody else have this happen.

 

[jtnm]

Check to see if the pellet is covering the transfer port or pellet probe. Mark the pellet probe with a sharpie while installed and bolt closed. Pull out barrel and probe. Insert probe to sharpie mark look at transfer port hole. If it’s covering you will have to adjust the length. 

 

[SniperM]

Thanks will have a look at that tonight. I did check the end of the probe and the mag clearence it was flush with the back of the frame where you insert mag. Will look at again with marks and see if there is a problem. I knew there should be a gain in speed but was surprised when it was slower then stock. Thanks for the info I appreciate it.

 

[Odoyle]

Had similar phenomena with other not FX specific brand type mod a long time ago when I used to be into tinkering. Haven't had a need nor desire to do this mod to an Impact but I wouldn't worry about it just bump the power up simple.

 

[Kurt110]

I installed both in my brand new Mk2 Impact .22. 600mm. Went from 938fps avg to 988 average with the same extreme spread with H&Ns 27 grainer. On the exact same settings 

 

[SniperM]

Thanks guys it was a timing issue. Talked with a guy at Huma he explained how and what to do. When i checked the openings were off adjusted got it spot on reassembled and now I get 970 on 5 with 34 grain slugs and the avg spread 6 fps on power wheel 2 fps with 26 gr is 930. More testing an tuning then to get it sighted back in and dope card made then to the woods.

 

[qball]

Very interesting, might have to try this. 

 

[jps2486]

The velocity on my MK2 went up 50 fps.