HELP me Tune my Mk2 PP .25 cal impact!

[RC_Bladeworks]

I have a fx impact (factory power plenum) in 25 cal shooting jsb mk2 33.95 king heavys. I have a 600 mm barrel. What reg setting and hammer adjuster distance should i shoot for? Ive been at it for a week and i can't get good consistent fps spread. Help!

 

[2manyAirGunz]

I have a fx impact (factory power plenum) in 25 cal shooting jsb mk2 33.95 king heavys. I have a 600 mm barrel. What reg setting and hammer adjuster distance should i shoot for? Ive been at it for a week and i can't get good consistent fps spread. Help!

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Have you checked this video:

https://airgun101.com/index.php/component/allvideoshare/video/fx-impact-power-plenum-tune-sight-in-for-long-range?Itemid=456

 

[JamieUK]

Hi RC,

If you havent watched the fx masterclass or 68whiskey tuning vids start there first...

You cant really be given a magic formula, depending on what fps you are looking for (880-920?) best bet would be to start at 125b/ valve at 4 with play in HSTA, walk up the HSTA until you stop seeing an increase in velocity. If you havent reached your desired fps increase reg pressure by 5b ( unless your miles off desired fps then increase by 10b)

Walk up the HSTA as before ( and then reg/ HSTA as required) until you are about 20 to 25fps above your desired fps. You should be on the right side of the curve at this point. You can then tighten your ES spread with the valve adjuster.

Unless you know all this already, in which case it sounds like you have an issue....

 

[RC_Bladeworks]

Hi RC,

If you havent watched the fx masterclass or 68whiskey tuning vids start there first...

You cant really be given a magic formula, depending on what fps you are looking for (880-920?) best bet would be to start at 125b/ valve at 4 with play in HSTA, walk up the HSTA until you stop seeing an increase in velocity. If you havent reached your desired fps increase reg pressure by 5b ( unless your miles off desired fps then increase by 10b)

Walk up the HSTA as before ( and then reg/ HSTA as required) until you are about 20 to 25fps above your desired fps. You should be on the right side of the curve at this point. You can then tighten your ES spread with the valve adjuster.

Unless you know all this already, in which case it sounds like you have an issue....

What's a good standard deviation to shoot for? Over how many shots? Does shooting too fast affect the results?

 

[JamieUK]

Someone with more knowledge will have to answer that one mate, I tune whilst shooting targets until I see a rough ES of around 10fps over a mag. After that I forget it and hunt....

 

[DShepard]

The final tune on my gun with the 700 barrel was 959 fps, ES of 4, 140-145 bar. 

 

[Drumsnguns]

My Impact is shooting JSB MKII at 870 with an ES of 6-7 and an SD of 1. This is exceptional. I achieved it by turning the valve in no more than 1/8 turn, (one line on the knob), each time and shooting over the chrony.

I would say an ES of 10 would be good and an ES of 10 to 15 would be considered decent. 

The lower the ES the better but if you're shooting slugs then I'd guess you might be hunting and shooting targets at distances over 100 yards, so ES 10-15 is probably fine for those needs. Better ES for competition shooting.

 

[Ginuwine1969]

What’s your Reg set at?