GBB pistol jump in FPS
 

I wouldn't really call this an issue or problem which is why I didn't post in the Doc section.

Got my KWA ATP about 2 weeks ago and when I first got it I got a chrono average of about 275 which I though was fairly low. Over the course of the past two weeks I have shot a couple hundred rounds and taken apart and cleaned and relubed as this gun comes fairly dry. Now my gun is consistently putting out a FPS of about 320 or so. (A 45fps jump from 2 weeks ago when I got it).

I guess my question is, is this normal for gbb to rise as the gun get's 'broken in' or is it a possiblity that as a gbb noob I may have been putting too much propane in the mag? (if thats even possible). Now I put a max of 3-4 sec of propane and it lasts about 3 full mags.

Wasn't really liking the 275fps when I first got it but now that it's risen to 320 it's been a nice surprise!

What was the ambient temperature when you chronoed it the first time and then the second time? If you were doing it outdoors both times and it was much colder the first time you tested it, and warmer the second time you tested it, this maybe be why. A big "maybe".

No I have my chrono set up indoors and have done every test from indoors. At first I thought it may have been just the temperature of the propane from the trip from walmart to home (but thats only about 5 min). I am thinking that as a gbb noob I filled the mag too full because at the beginning I was seeing some propane shoot out of the ejection port on my first few shots. But I chronoed 2 mags straight so even when the mag was only filled up about half with the propane it was still shooting sub 300fps. It has been rising over the past 2 weeks and seems to have settled around the 215 - 225 mark.

You can't fill it too full. When liquid propane spits out of the fill valve, it's full and can't be filled more. I can't be bothered to count do I just wait until it spit propane or I listen until I can't hear it transferring anymore.

How many different weight BB's do you own? Have you used a different weight by accident?

Was it a new/full tank of propane vs. a half full tank?

It's also possible that his hop up rubber has swelled a bit and is causing a better seal... Just playing devils advocate... FPS raise is odd.

True, with the regular take downs and frequent lubing, could be creating better seals all around

Full tank of propane and using .20 bioval bb's. I tried some of the .20 red dyed Ultimate Airsoft bb's also. Both were shooting the same fps. As you guys implied I too believe that it is just a fact of the gun being better lubed. The ATP is notorious for coming very dry from the factory I hear.

probably a seal getting worked a bit softer and settling in to do its job. the other thing is depending on the type of chrono, some chronos will see a puff of gas and measure it before it measures the BB. you could have had a 270fps puff.

I have a hell of a time trying to chrono my 226 because the chrono sees the gas more often than not... and then when you hold it farther out, the BB never goes through cleanly.

Its an xcortech 3200. I understand what you are talking about and makes sense but I don't think that was what was happening. (but possible). I would shoot full mags thru with the fps at that 275 range. The next day it went up and then a few days later it hit the 300fps range. Kinda surprised me but I just figured it was the 'working-in' of the gun. Like i said before i have done about 3 takedowns and put new silicon oils and greases on the gun. To me the swelling of the seals makes the most probable cause as it would take time for the seals to expand a bit....i guess...haha

I agree with the above theories of lubing seals. KWA's shoot pretty hot for pistols so seeing it shoot 275fps would raise some questions. 320-350 is more normal for KWA pistols.