FPS jumps up, what can be the cause...

I have the same sort of issue when shooting over the chrony. Shots will be pretty close to each other firing from the same mag. Except #1. But the first shot out of the second mag will be high. The rest of the mag will be ok. Figured it out. I wasn’t waiting long enough between shots. But when I took longer to insert the second mag, my 1st shot was higher. I now count to 5 or so before pulling the trigger. All shots from both mags are close. I can really see this when shooting 4 mage in the Prod. Shots 1,11, 21 and 31 are faster then the rest of the mags. I also know this is worse when regulated. 

try to sort your pellets by weight

I have been trying to tune my .25 FX Impact today but noticed that 1 out of lets say 5 shots will be a much higher FPS for example.

902

910

905

912

923 <----

905

904

909

930 <----

what would cause something like this? 

I do have a C3 delrin installed and I have checked it.

This happens even with hammer stopper fully open



Thank!

Click to expand...

I’m glad you posted this and I’m even happier that I read it .I was tuning my prod today and ran into this same problem. Thanks

I have been trying to tune my .25 FX Impact today but noticed that 1 out of lets say 5 shots will be a much higher FPS for example.

902

910

905

912

923 <----

905

904

909

930 <----

what would cause something like this? 

I do have a C3 delrin installed and I have checked it.

This happens even with hammer stopper fully open



Thank!

Click to expand...

I’m glad you posted this and I’m even happier that I read it .I was tuning my prod today and ran into this same problem. Thanks

Click to expand...

My guess is that you both are shooting pellets? These speeding pellets are smaller. If you weight sort them you should eliminate the random faster speed. Sort to the tenth of a grain and shoot the same weight until gone and move up or down from there.

Hum, MKi or MKiX or MKii or PPMKii, where's your regulator set? On which line is the valve adjustment at? How much slack is in the hammer grub screw when set to max? What pellet? What croine? What barrel?

I've never had any luck sorting pellets for fps changes.

I guessing, MKII, Jsb's 25.4 grain pellets. 600mm barrel, 140-145bar on the regular. Grub screw .060 slack on max, 3.5 line on the valve adjustment.

We can help, there small difference's that will help us help you

One other question. Was there more time between the shots with the higher velocity? Could you have a slow regulator? Is the first shot high when you fill it and it sits?

On the impact, it will probably help to turn in the valve stop, until the average velocity drops some.

I just got through going through a very similar ordeal and what I found is what tor47 recommended.

Jimmy