received my impact .25 from SPAW a few days ago. He tested with jsb 33.95s. I am shooting jsb 25.39s. Reg came set at 100. Valve at 4th line. Average 894 FPS. My first shot was 1010 FPS at max wheel and stayed right around there. 
What would you guys do to get it down? It doesn’t shoot good at that high FPS. I increased reg and lowered the hammer and it’s better now but I am new to tuning so just want to make sure I am on the right path.
Impact PP tuning help needed
- Thread starter b121774
- Start date
Mine came from Utah airguns with the reg set at 90#, wheel on 3 and shooting the 25.9 at 920FPS. Not sure which valve line it is on. Shoots very accurate though.
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Just turn the valve adjuster in a bit to lower speed. Its probably tuned to shoot the heavies at around 900, lower the hammer spring wheel and/or turn in the valve adjuster a turn or so.
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I wouldn't recommend increasing the regulator pressure to slow it down, I'd lower the pressure down to 80-85bar ( remove the bottle and dump the gun the starting point of the regulator will be about 1/2 of a turn CC out from fully in tight) start the Va at the 4th line and the hammer on 1. Shoot 5-6 shots over the cronie, click the hammer up to 2 then take a couple of shoots if the fps stay the same,inch the regulator up 2-3bar and turn down the hammer to 1. If it increases speed when hammer is click up. Click it up until it stops building speed, click down one level and then turn up the regulator. Then start over with 5 shoots. When you get to 10-15fps over your goal start turning the Va in 1/8th of a turn for each 3-4 shoots until nice consistent shoot start coming near your goal. If you go to far the speed gets jumpy
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With your reg set at 100, I would think just taking some spring off the hammer should do the job. (Different chronos may give different readings).
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This is what you can expect according to Ernest.
What you can expect from a stock .25 cal 700mm with power plenum at 160b with all adjustment at max:
1. 38.5gn slug 960fps
2. 36.2gn slug 975fps
3. 33.2gn slug 1000fps
4. 29gn slug 1040fps
5. 26gn slug 1070fps
6. 33.9gn pellet 1000fps
your speed my very with each impact have different tolerance. 52mm or 57mm hammer spring or 16mm or 18mm HSTA
Ernest
What you can expect from a stock .25 cal 700mm with power plenum at 160b with all adjustment at max:
1. 38.5gn slug 960fps
2. 36.2gn slug 975fps
3. 33.2gn slug 1000fps
4. 29gn slug 1040fps
5. 26gn slug 1070fps
6. 33.9gn pellet 1000fps
your speed my very with each impact have different tolerance. 52mm or 57mm hammer spring or 16mm or 18mm HSTA
Ernest
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