Daystate owners

I've have noticed that my Air Ranger 80 will only
seal up when I use the O-rings that are purchased
from Daystate they seem to be a little thicker in the 
outside diameter ( darn that metric system ) .

Something you could try is to polish the lead in your barrel 
Daystate does leave the rifling in the barrel and your probe 
o-ring is always grinding across the rifling in the barrel .
 
It appears that you have two different guns of different manufacturers in which both have recently experienced a velocity drop within the last one to two months time, a Daystate and a Kaliburgun.
Based on this fact alone, I would suggest you check your chrony and always shoot at a consistent set distance from the muzzle and chrony test at the same location such as your home or at the range as a set constant to be sure you are not trying to compare numbers at different altitudes or temperatures.
 
Yes my cricket was leaking, I sent it back they fixed but is not giving me the speed that he said, but is only 28 fps slower than what i was told.. and my daystate has been dropping fps a while ago I sended to Airguns of Arizona to be checked and they told me that it was shooting 820 when I bough it it was shooting 840, now it is shooting 790fps so that means that is getting worse.. I got a new chrony to make sure that wasn't me doing mistakes,, I did a test puting a little piece of paper on the bridge and it fly away when I fire the pellet. Anyway I will contact AOA .. thanks to everyone for the advices,I'm new to the airguns hobby, I have a lot to learn..