Canadian Airgun Forum

found out the ruger airhalk shoots over the legal limit with 520 fps with 7.8 grain pellets and 640 with those crosman high velocity pellets. i don't think it is dieseling or anything, just thought it was weird a Canadian airgun shoots that fast. anyone else choreographed their ruger airhalk before, or whatever Diana model its a clone of? just wanted to know if you've had similar results.

Hi.
It's difficult to tune or detune a springer (any gun for that matter) to shoot 495 fps since there is so much variability in the system. It is not unusual to chrony a non PAL (springer in particular) and get numbers above 500 fps. Two major reasons could be: dieseling caused by combustible oil and grease in the compression chamber and barrel, and light weight pellets.
You can prevent dieseling with a good clean out and use only silicone oil in the compression chamber and no combustible oil or grease in the barrel. Chrony with standard weight pellets after a break in period of about 250 pellets afterward. Standard weight in .177 would be those around 7.9 gr.
And yes it happens that you may still be slightly over 500 fps. As long as you haven't shimmed the spring or plugged a bleed hole I wouldn't worry about it.
And the Air Hawk is based on the Diana 34, but isn't a 100% clone, meaning not all parts are interchangeable. Springs, piston seals are interchangeable. I believe stocks are not, and cocking arms are not as well.

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Well it would be nice as Canadians if we were told the exact pellet weight tested for fps checks...
I've heard 7.4 as the .177 standard and also .7.9...since you did not alter the gun I assume you would be okay...Myself I have a pal anyway but if I didn't I'd probably lop off a coil......just to be on the safe side...it is odd though..never heard of one shooting over before...sometimes they are well below the 495 mark

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The cave you fear to enter....holds the treasure you seek

If you don't think its dieseling. I think issue with your chrony.

Since mine out of the box shot around 480 FPS with 7.9grns and 7.4s was still under 500. I put a full power spring and 8.4 grns was 880 FPS.

Mine shot 510-520 fps C de-tuned version with 7.9gr no matter licensed for all.