Jsb .25 heavys in fx impact settings?

Trying to shoot the 33.95 grain heavys out of my impact but struggling to get them to shoot consistent speeds at 840-850 fps range. I was curious of what you guys have set the regulator at and how big your hammer spring gap is. I currently have mine set at 17.1mm and reg at roughly 135-140 hard to really tell on the stock guage. Ive got them at the speed i want but i can just tell the gun doesnt feel great, speeds are kinda inconsistent. I had the 25 grainer shooting 905 fps with a spread of 7fps and deviation of 1.9 and you could just feel the gun liked it.
 
I found my best success mark2
set power wheel on max making sure adjustment screw has 99% of play out.
my reg is on 130 works for me
start w/ valve on 3 and turn out while shooting over chrony
when you get max fps start shooting group while dialing down wheel
when you find best group [mine is 4) note your fps 
Now if you think it can be better (if you're 1/2" @50 quit) you can decrease or increase valve for fine tuning fps.
mine likes 870-875. All barrels are individual.
after shooting a few 1000 youll figure it out!
Barrel fully seated and tight, check it. These are race cars and must be monitored constantly.
 
"Dts327"I settled on 836 average fps with the mk1, shot a 10 shot 3/8th inch group @50 with them. I should get the mk2s in the mail today so ill take your advice about the hammer spring and take some more slack out of it, id really like to find accuracy around 850-860 fps
I personally wouldn't touch your setup. What works for someone else might not work for you. I know you want a little faster, but 20fps isn't much of a difference and definitely not enough to mess with an accurately shooting setup.
 
Dts327, man if I was getting groups like that with MK I's I wouldn't bother with the II's. I think you're there. Don't touch it..haha. Also, I don't think an extra 15-20 fps is gonna make a difference. Like EliteAirgunr said, all our guns are different. 

CHUCK, on the HUMA REGULATOR thread said MKII's do great at 880-900 out of his Streamline and Wildcat. I tried it and they don't do so great at that speed out of the Impact. Wish they did but I'm actually happy to save on air consumption between 830-860. 

I need to start all over again and try Matt Dubber's regulator harmonic tuning but FX states in their Impact troubleshooting pamphlet, (for .25 cal), to set the regulator to 120 bar and the hammer spring gap to 18.00 mm and I think they are very close to spot on...I'm sure they have researched this setting to be best. A little bit of tweeking to get the hammer spring hitting at the ideal force for a particular reg setting may be needed but just a little and sounds like your setting of 17.1 mm is legit.

KP

 
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DrumsngunsDts327, man if I was getting groups like that with MK I's I wouldn't bother with the II's. I think you're there. 

I got the mkII in the mail and have shot about 100 or so and they shoot about as good as the 25gr kings. Kinda disappointed lol most people seem to say they are better then the mkI but i guess my gun just prefers the longer skirts of the mkI. Heres a pretty consistent 50 yard 10 shot group with them